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THE PEANUT—
THE UNPREDICTABLE LEGUME

THE PEANUT

THE UNPREDICTABLE LEGUME

A SYMPOSIUM

Prepared by
FRANK SELMAN ARANT _ B. B. HIGGINS
ROGER W. BLEDSOE BEN W. SMITH
W. E. COLWELL D. G. STURKIE
KENNETH H. GARREN J. T. WILLIAMSON
WALTON C, GREGORY COYT WILSON
HENRY C. HARRIS JOHN A. YARBROUGH

E. T. YORK, JR.

Sponsored by
THE PLANT FOOD RESEARCH COMMITTEE OF
THE NATIONAL FERTILIZER ASSOCIATION
Published by
THE NATIONAL FERTILIZER ASSOCIATION

WASHINGTON, D. C.

MAL

right to reproduce this book, or portions thereof,
in any form.

S38

35]
P3
P3s

PRINTED IN THE UNITED STATES OF AMERICA
First Printing 1951

178301

Typography, Layout and Printing by

THE WILLIAM Byrp Press, INc.
RicHMOND, Va.

The National Fertilizer Association
and the chapter authors
take pleasure in dedicating this book
to the advancement of American Agriculture

PREFACE

Tue PEANUT—THE UnprepicTasLe LecumeE has brought together
between two covers authoritative information on this crop. From a mass
of data, much of which is contradictory, inconsistent and erratic, here is
presented a consolidation and interpretation of present-day ideas which
forms a sound foundation for further needed research on the economic
production of peanuts—the most peculiar of all major farm crops. This
volume is a valuable contribution to the understanding of the peanut
plant and its economic production. It should not be construed as an end
point to the problems in agronomy, plant nutrition, plant physiology,
plant pathology, biochemistry, agricultural engineering and entomology.
Many of such problems, however, are clarified by the material presented.

Generous credit is due the chapter authors upon whom the burden of
preparing the subject matter fell. Years of patient work in consolidating
and interpreting the results in each field of investigation are represented
by THE PEANUT—THE UNPREDICTABLE LEGUME. The con-
tributions of the chapter authors have been unselfishly made in the in-
terest of the advancement of agricultural science. They deserve the grati-
tude of all producers, processors and consumers of peanuts.

The development of this volume began in 1937 when the great prob-
lems of varying results involving fertilizer field trials engaged the atten-
tion of the Plant Food Research Committee of The National Fertilizer
Association. The need for more research was presented to and approved
by the Southeastern Agronomy Research Committee of the Southeastern
Experiment Stations, January 31, 1939. Then followed a series of confer-
ences of research workers. These scientists contributed data and obser-
vations which stimulated new research and clarified previous findings.
Annual conferences were held from 1939 to 1944, inclusive, and, after a
year’s omission, were resumed in 1946 and continued through 1948.

Personalities involved in the many investigations and contributing to
the understanding of peanut production problems at the various con-
ferences included many distinguished authorities.

Chairmen of the conferences during the various years were: W. E.
Stokes, Florida Agricultural Experiment Station, N. J. Volk, Alabama
Agricultural Experiment Station, and R. W. Cummings, North Carolina

Vili THE PEANUT—THE UNPREDICTABLE LEGUME

Agricultural Experiment Station, all of whom gave generously of their
time.

Financial support for the annual conferences and for the publication
of this book was contributed by The National Fertilizer Association.

It would be a great injustice not to recognize the efficient work of
H. R. Smalley, R. H. Lush and M. H. McVickar, all of The National
Fertilizer Association, who served as secretaries of the various confer-
ences.

Members of the Plant Food Research Committee of The National
Fertilizer Association who served on the Peanut Research Committee at
various times include: T. F, Bridgers, C. J. Cahill, Leroy Donald, Myron
S. Hazen, G. N. Hoffer, Frank L. Holland, Wallace Macfarlane, H. B.
Mann, R. D. Martenet, F. W. Parker, J. R. Taylor and the undersigned
Chairman.

Respectfully submitted,
Davin D. Lone, Chairman
Subcommittee Peanut Fertilization
Plant Food Research Committee
The National Fertilizer Association

CONTENTS

PAGE
PREFACE . www eV
CHAPTER I
Economic IMporTANCE OF PEANUTS . . . . . 3
B, B. Higgins
CHAPTER II
ORIGIN AND EARLY History oF THE PEANUT . . .... 18
B. B. Higgins

CHAPTER III

~ MorpHotocy, GENETICS AND BREEDING é ‘ 28
Walton C. Gregory, Ben W. Smith, John A. Po chndua

CHAPTER IV
PHysIOLOGY AND MINERAL NUTRITION . . . . . . 89
Henry C. Harris, Roger W. Bledsoe . 4
CHAPTER V 2
Soi. Properties, FERTILIZATION AND MAINTENANCE OF SOIL
Fertility . . Sh tag, 1) Ma gee, tt, “ns, le

E. T. York, Jr., W. E Colwell

CHAPTER VI
CULTURAL PRACTICES .. “ee ae Oe Oat. See Ge, ES

D. G. Sturkie, J. T. Walllamsam

CHAPTER VII

Insect Pests .. me es RS OR Ate OS eds 3 6: SEO
Frank Selman or

CHAPTER VIII

Peanut DISEASES .. oe. Gowe Se. Se <a 3262
‘Kenneth H. Garren, Coyt Wilson

THE PEANUT—
THE UNPREDICTABLE LEGUME

; CHAPTER I

ECONOMIC IMPORTANCE
OF PEANUTS

B. B. HIGGINS?

The peanut is generally recognized as one of the important crop
plants of the world. This recognition has arrived very slowly. Although
the plant has been known to Europeans since the sixteenth century, it
was only approximately 100 years ago that the oil mills of Marseilles,
France, began importing and crushing peanuts grown in North Africa.
This may be considered the beginning of large-scale industrial use of the
crop, though an oil mill was established at Valencia, Spain, 50 years
earlier (7). The desirable qualities of the peanut oil brought early success
to the enterprise, and mills for crushing peanuts were quickly established
in other European countries. Since then, the commerce in peanuts has
expanded slowly to its present proportions. In 1947 the commercial crop
of the world amounted to 10,579,000 tons.

The relative importance of the producing areas of the world is shown
in table 1. While figures given for many countries are admittedly only
estimates, they do indicate the relative importance of various world areas
insofar as the commercial production of peanuts is concerned. They in-
dicate that the peanut is now an important crop in the warmer areas of all
six continents of the world. The wofld trade depends largely on the
European demand for oil. India, China, Burma, Sumatra, Java, and the
French African colonies have long been the principal exporters of peanuts.
At present, the supply is inadequate to meet the demand. World War II
so upset and confused agricultural production in Europe that there is an
enormous shortage of edible fats and oils. Increased production of peanut
oil appears to offer the most feasible possibility for early and permanent

1B. B. Higgins is botanist, Georgia Agricultural Experiment Station.

4 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 1.—PEANUT ACREAGE AND PRODUCTION IN SPECIFIED AREAS AND COUNTRIES.*
Sources of data: Foreign Crops and Markets, U. S. Dept. Agri. 55 (22): 371-373;

57 (22): 427-430.

Average
Average 1935-39 Average 1943-47 1943-47
Continent and
Countries Acreage | Production Acreage | Production | Acre
Yield
acres tons acres tons pounds
North America
Mexico............ 33 ,000 12,200 98 , 333 43,750 890
United States..... .| 1,659,000 614,700 | 3,409,000 | 1,052,580 618
Ch ene = 3,400 95,800 27,200 | 568
Dominican Republic — 3,800 35,400 8,180 462
Total>......... 1,800,000 640,000 | 3,494,000 | 1,136,200 650
Europe
Bulgaria........... 5,000 2,200 3,400 940 553
Tiel Ausine shes 2,000 1,600 7,600 5,320 | 1,400
SPAIN oi o.a chow 24 ,000 23,300 16,333 11,433 | 1,400
Total’. ........ 35,000 28,000 33 ,000 20,000 | 1,212
Russia
(Europe & Asia).... 29 ,000 _— _ = _
Asia
Burma............ 784 ,000 192,200 636 ,250 127,050 399
China proper... ... 3,639,000 | 2,913,400 | 3,444,000 | 2,614,300 | 1,518
Manchuria........ — 121,600 — — —
French India......... 7,000 5,600 7,000 5,633 | 1,609
French Indo China. 42,000 16,000 107 ,000 27,000 505
Dad ibe ccce anes tins 7,535,000 | 3,295,700 |10,123,800 | 4,005,258 791
Japan proper...... 19 ,000 14,600 —_ 19 ,800 —_—
Formosa.......... 77,000 57,700 —_ —_ —_—
Kwantung......... 101 ,000 91,100 _— — —_
Netherlands Indies. 572,000 289 ,100 430 ,400 190 ,440 885
Philippine Islands. . 18 ,000 4,700 — — —_—
Total auasaeine 13,200,000 | 7,040,000 |15,238,000 | 7,246,600 | 951
South America
Argentina......... 207 ,000 87 ,300 330 , 800 154,120 932
Brazile. cs sionden tue — 14,800 87 ,000 34,133 785
Paraguay.......... 29 ,000 19 ,400 21,500 13,250 | 1,233
Uruguay.......... 5,000 1,200 16 ,400 4,700 573
Total> 400 ,000 129,000 520 ,000 208 ,000 800
Africa
Anglo-Egyptian’
udan........... 43,000 8,100 55,000 500 418
Belgian Congo..... 245 ,000 65,100 540 ,000 —_ —
Tanganyika........ 277,000 23 ,400¢ — 6 ,620¢ _
Uganda........... 156,000 2,200°| 333,333 9,550°) —
Gambia........... — 58,100 —_ 84,900 —_—
Evy pt.cesoeeax as si 23 ,000 17,200 25,800 19,760 | 1,532
Fr. Equatorial
Africa and
Cameroun....... 388 ,000 58 , 800 —_ _ _—

ECONOMIC IMPORTANCE OF PEANUTS 5

Table 1—Continued

Average
. Average 1935-39 Average 1943-47 1943-47
Continent and -
Countries Acreage | Production | Acreage | Production | Acre
: Vield
acres tons acres tons pounds
Fr. West Africa... .| 2,955,000 875,900 — 527,340 _
Madagascar....... 14,000 6,600 26 ,400 7,980 605
Mozambique....... — 42 ,900° _— 19,525 —_—
Nigeria and
Cameroons...... _— 354, 700°} 2,500,000 538 ,400° 431
Angola............ 18,000 6,200 — 7,267 =
Portuguese Guinea —_ 28 ,000¢ —_ 33 ,733 —_
Union of South
Africa........... 56,000 12,000 95,000. 22,600 | 476
Totalb......... 6,120,000 | 1,673,000 | 6,000,000 | 1,461,600 | 487
Oceana
Australia.......... 14,000 6,100 23 ,800 23,900 | 1,168
Totalb......... 15,000 6,500 27,200 13,800 | 1,015
Wor .p ToTAL....... 21,600,000 | 9,531,000 |25,380,000 |10,090,600 795

® Harvested crop statistics not complete for all years of periods covered,
b Continental totals include estimates for other minor producing countries.
° Exports only.

relief. A large government-sponsored project for increased peanut pro-
duction in the Belgian Congo is already in operation ; another, sponsored
by the British Government, has for its objective the mechanized produc-
tion of peanuts on 3 million acres in Tanganyika and Northern Rhodesia ;
and production in French West Africa and Nigeria is being vastly
expanded.

Previous to development of the peanut oil industry, the world trade
in peanuts was unimportant. However, in every country where grown,
they were considered an important item of food and considerable local
trade sprang up. The peanuts were most commonly roasted in the shell
and sold for immediate consumption. They were also used for making
candy and other confections. While a peanut paste similar to peanut
butter was apparently made and used by the South American Indians,
utilization of peanuts in this type of product has not reached commercial
importance except in the United States. In Spain and in some Spanish-
American countries, peanuts are ground, mixed with cocoa or with
honey and utilized for food; but exact data as to the extent of this utili-
zation are not available.

6 THE PEANUT—THE UNPREDICTABLE LEGUME

DEVELOPMENT OF THE PEANUT INDUSTRY
IN THE UNITED STATES

“Groundnuts” are mentioned (19, 20) in some of our earliest Colonial
records, but this name was used for other plants as well as for peanuts,
“and we are often not sure what plant was indicated. Whether or not
peanuts were grown within the present limits of the United States by the
Indians of pre-Columbian times is still questionable, but we do have
authentic records of peanut culture during Colonial days. The following
quotation from a report by Sir William Watson (27) to the Royal Society
and published in the Philosophical Transactions for October 1769 is of
special interest :

“It is with this view, that I lay before you some pods of a vegetable
and the oil pressed from them. They were sent from Edenton, in North
Carolina, by George Brownrigg, whose brother, Dr. Brownrigg, is a
worthy member of our Society; and are the produce of a plant well
known and much cultivated in the Southern colonies and in our American
sugar islands, where they are called groundnuts, or ground pease. .. .
Mr. Brownrigg, from whom as I before mentioned, I received the oil,
considers the expressing oil from the ground pease, as a discovery of his
own: It may, perhaps, at this time, be very little practiced either in
North Carolina, the place of his residence, or elsewhere. But certain it
is that this oil was expressed above fourscore years ago; as Sir Hans
Sloane mentions it, in the first volume of his History of Jamaica; and
says that this oil is as good as that of almonds. . . . After the oil has
been expressed from the ground pease, they are yet excellent food for
swine.”

Thomas Jefferson (6) mentioned peanuts as being commonly
grown in Virginia, but implied that the crop was of little importance
Commercially. Before the Civil War, they were grown commercially
at least for local consumption throughout the South and even in Cali-
fornia. Ramsey (23) in his history of South Carolina, 1809, mentioned
among vegetables, groundnuts used as a food, as a substitute for cocoa,
and as a source of oil for domestic use. In discussing Edisto-Island, he
again mentioned groundnuts, saying, “They are planted in small patches
chiefly by negroes for market. They produce 80 bushels per acre. They
are commonly sold for five shillings sterling per bushel. . . . price in
1768 was eight pence sterling per bushel.” The fact that they were being
grown commercially in South Carolina is shown also from records of
exports from the port of Charleston. We find a shipment of 51 casks of

ECONOMIC IMPORTANCE OF PEANUTS 7

groundnuts recorded (8) for the year November 1786 to November
1787. Williams (28), in discussing the agriculture of the Territory of
Florida (1830) says: ‘““The peanut produces a large crop and is a useful
article in the dessert.” Burke (9), in describing life on a slave-operated
plantation near Savannah, Georgia, during the first half of the nineteenth
century, says: “Great quantities of peanuts are raised there, not only as
an article of export, but to fatten swine upon. They are planted in the
Same manner as potatoes and when they have come to maturity the
swine are turned in upon them to dig their own food. It is not usual for
planters to feed their swine in any other way. . . .”

Several others writing from Georgia (4, 23), Alabama (13), Missis-
sippi (22), Louisiana (17) and California (5).at about this date spoke
of peanuts as a valuable crop, especially for hog feed. In 1851, W. B.
Easby (15) of Vernon, Tennessee, wrote: “The goober pea is extensively
raised here, and so far has proved the most profitable crop that can be
raised. The first ever raised for market was sold in Nashville in the fall of
1845. Since that time there has been upwards of 20,000 to 25,000 bushels
raised within 10 to 15 miles of this place each year, and sell for 65 cents
to one dollar per 22 pounds. The vine is equal to clover hay for stock, if
well saved.”

During and after the Civil War commercial production increased
rapidly. Exact statistical records for the period are not available, but
in the Annual Report of the U. S. Department of Agriculture for 1868 +
is found a 4-page discussion of the crop. It is stated that the Virginia |
crop for that year was estimated at 300,000 bushels, selling at $2.75 a
bushel (22 pounds). Two varieties are mentioned: Virginia and the
Carolina or African:

At this time most of the commercial crop was roasted in the shell
and sold freshly roasted by street vendors. The work of harvesting, pick-
ing and preparing for market was all done by hand or with crude home-
made equipment. Lack of commercial shellers undoubtedly retarded
utilization of peanuts. Lack of uniformity and poor quality discouraged
trade in peanuts even for roasting. Some farmers built crude equipment
for scrubbing and shaking dirt from the peanuts and blowing out trash
and “pops,” and hand-picked the discolored nuts; but this practice for
improving the uniformity and quality of the product was not general.
In 1870, P. D. Gwaltney (7) began buying peanuts from growers about
Smithfield, Virginia, cleaning them as best he could with such crude
equipment as available, and reselling. Ten years later, he, in partnership
with A. Bunkley, built what is said to have been the first factory for

8 THE PEANUT—THE UNPREDICTABLE LEGUME

cleaning, grading, and polishing peanuts to be roasted in the shell. Ap-
parently, however, another factory was built in New York City about the
same date (21), probably for cleaning imported stock.

Figure 1—Typical modern peanut processing plant.

More important for development of the peanut industry was the in-
vention and manufacture of machinery for planting, cultivating and
harvesting the plant, picking the nuts from the plants, and for shelling
and cleaning the seed. Without these labor-saving machines, peanut
production would undoubtedly have declined with the gradual increase
in cost of human labor. In 1872, H. E. Colton (12) writing about pea-
nuts, said that under stress of producing peanuts for oil during the Civil
War, a mechanic, Thomas L. Colville of Wilmington, North Carolina,
built machines for threshing the nuts from the vines and winnowing them
and also built machines for removing the shells. Neither machine was
patented and many variations and improvements were tried before a
really satisfactory picker was built about the beginning of the present
century. Development of a successful planter, of the scraper plow, the
weeder, and the peanut wing for cutting the roots in harvesting, are
among the important inventions that materially reduced the labor of
producing peanuts and led to vast expansion of the peanut industry
during the present century. The mechanical sheller has been an espe-
cially important factor in increasing the use of peanuts and peanut pro-
ducts such as peanut oil, roasted and salted nuts, peanut butter, peanut
candy, and other confections.

ECONOMIC IMPORTANCE OF PEANUTS 9

Apparently pre-Columbian Indians of America (14) and the African
natives (11) made and used both peanut oil and a peanut paste com-
parable with our peanut butter long before the white man used either
product. Apparently, peanut butter was first made commercially about
1890 by a physician (25) in St. Louis, Missouri, who prescribed it for
some of his patients as a nutritious, easily digested, high-protein food, low
in carbohydrates. The idea spread rapidly. Winton (29), in 1899,
published analyses of two brands; and in 1914, Utt (26) analyzed and
examined for adulterants 23 brands bought on the markets of Kansas
City. At present, more than half the peanuts shelled for the edible trade
go into the production of peanut butter.

The increased need for oil for various uses in time of war has caused
great expansion of peanut production during each such, period since
1860, and other uses have usually absorbed the increase in each sub-
sequent period. Several writers agree that rapid expansion occurred
between 1860 and 1870. Again referring to the article by Colton (12),
published in 1872, we read: “Instead of 1,000 there are fully 550,000
bushels sold annually in the city of New York alone. Previous to 1860,
the total production of the United States did not amount to more than
150,000 bushels, and of this total fully five-sixths were from North Caro-
lina. Now, North Carolina produces 125,000 bushels; Virginia, 300,000
bushels; Tennessee, 50,000 bushels; Georgia and South Carolina, each,
25,000 bushels; while from Africa come about 100,000 bushels a year.”
We may feel inclined to doubt Colton’s data, but his estimates as to the
size and the distribution of the industry cover a period for which we
have no authentic records. It seems probable that the estimates were
based on only that portion of the crop which entered interstate commerce,
since statistics on crop acreage in Georgia, furnished by the Comptroller
General to the Georgia Agricultural Society (6), gave for the peanut crop
16,619 acres in 1873 and 21,162 acres in 1874, several times the acreage
necessary to produce 25,000 bushels.

: Acreage and production of peanuts are recorded in the Eleventh
Census Report for the year 1889, and are included in all subsequent
enumerations. The U. S. Department of Agriculture, through its system
of crop estimates, has kept fairly accurate annual records of total acreage
planted, acreage harvested, and the production by States. During the
period of acreage limitation, from 1934 to 1942, more exact data were
obtained as to the harvested acreage and production.

“In order to facilitate marketing the crop, three producing areas have
been designated: The Virginia-Carolina area, including Virginia, North

10 THE PEANUT—THE UNPREDICTABLE LEGUME

Carolina, and Tennessee; the Southeastern area, including South Caro-
lina, Georgia, Florida, Alabama and Mississippi; and the Southwestern
area, including Louisiana, Arkansas, Texas, Oklahoma and New Mexico
(figure 2). The division into these three areas is based somewhat upon
the type of peanut grown. The Virginia-Carolina area produces the
Virginia-type peanut almost exclusively, while it is, at present, of minor
importance in the other two areas. In the Southeastern area, the small
Spanish type constitutes the major portion of the commercial crop. A
small seeded runner of the African type is grown under several varietal
names and enters the trade as “Southeastern Runner.” The Virginia-
type peanut is grown in Bulloch County, Georgia, and to a less extent in
a few other localities. In the Southwestern area, the commercial crop is
almost exclusively of the Spanish type, though a small acreage of Tennes-
see Red is grown in New Mexico. See table 2 for varietal distribution.

Data in table 3 show something of the development of peanut pro-
duction for the country as a whole and for the seven States that account
for about 90 percent of the total tonnage of the country. It is of interest
to note the slight increase of acreage in Virginia and North Carolina
during the World War II period in contrast with the enormous expan-
sion in certain States of the Southeastern and Southwestern areas. This is
probably due to the restricted adaptability of the Virginia type in con-
trast with the more widely adapted Spanish ; and also to concentration of
peanut acreage. Over the past 20 years the planted acreage has surpassed
that harvested by about a million acres: Georgia, 400,000 to 600,000
acres; Florida, 150,000 to 300,000; and Alabama, about the same as
Florida, with scattered acreage in most other States of the South, grown
specifically for hog grazing.

According to the 1890 Census Report, some acreage of peanuts was
grown in 34 States the previous year, and some acreage was reported
from practically every county of the Cotton Belt. In the 1945 Census of
Agriculture, some acreage was reported in 32 States. The distribution of
this acreage, shown in figure 2, indicates all States in which 1,000 or
more acres were reported. In most of the 32 States plantings consisted of
small plots for home use only.

One can only guess as to how the peanut industry would have de-
veloped under the system of free competition prevalent prior to 1933. At
that time the policy of government guarantee of a base price, in consid-
eration of acreage limitation by growers of major farm crops, caused a
slight decrease in acreage; but this decrease had been overcome by 1939.
During the war years the abnormal demand for food by our own armed

ECONOMIC IMPORTANCE OF PEANUTS

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12 THE PEANUT—THE UNPREDICTABLE LEGUME

forces and those of our allies was such that government controls became
inoperative between 1943 and 1947. This demand at high prices caused
enormous expansion in most producing areas. Lack of machinery, espe-
cially pickers, for handling the crop and lack of marketing facilities pre-
vented expansion outside the old producing areas. With these limitations
removed, production within the United States could easily be doubled
again.

At present prices, No. 1 grade peanuts cannot profitably be crushed
for oil; and comparatively few peanuts of this grade are used for
such purpose. Those crushed are, for the most part, “off-grade” lots and
screenings, shrivels, splits and pick-outs from shelled No. 1 grade. As
an example, the proportional distribution (29) of the 1947 crop to vari-
ous usages is shown in figure 3.

HOME

16%

CRUSHED

pene ee

<
D>

Figure 3.—Proportional distribution of 1947 peanut crop to various usages.

Of the one and one-half billion pounds listed as cleaned and shelled,
80 million pounds were merely cleaned for roasting in the shell. These
were mostly Virginia-type, but included a few of other types. The distri-
bution by varieties in the shelled edible trade follows:

ECONOMIC IMPORTANCE OF PEANUTS 13

Table 2.—DISTRIBUTION BY VARIETIES IN THE SHELLED EDIBLE TRADE

Pounds Percent

Wirginias: so arch gia a gaa ee REET ase ee 174,131,000 22.6
Southeastern Runner............. 0.00. cess eee eee 193 ,904 ,000 25.2
Spanish............... ToRdis HA EE Ags Sham na are ees 401 ,224 ,000 52.2
POtaleicdeicc toni ove enoah seed healt Sees Ganeeds 769 ,259 ,000 100.0

Of this total, 189,683,000 pounds were exported, leaving 579,576,000 pounds for domestic use.

Table 3.—ACREAGE AND PRODUCTION IN THE UNITED STATES AND IN EACH OF THE
PRINCIPAL PRODUCING STATES FOR SPECIFIED YEARS BETWEEN 1889 AND 1947.

Acreage Harvested (000 acres)
Year
U.S. Va. N.C, Ga. Fila. Ala. Texas Okla.
18898 204 59 18 52 26 24 2 b
18992 517 | 117 96 100 69 79 11 2
1909 537 145 180 45 15 60 48 1
1919 919 | 133 126 201 55 300 90 8
1929 1,269 | 153 220 375 51 213 142 50
1939 1,787 | 148 245 670 85 300 322 53
1940 2,052 | 158 257 730 90 310 335 82
1941 1,900 | 134 229 650 85 315 340 72
1942 3,362 | 148 270 1,060 | 115 516 870 218
1943 3,492 150 300 1,127 110 574 850 200
1944 3,068 | 154 295 1,050 | 100 _ 520 680 178
1945 3,160 159 320 1,070 100 487 750 185
1946 | °3,142 | 150 295 1,070 95 472 767 221
1947 3,389 | 162 292 1,092 | 105 452 877 325
Production, Harvested Nuts (000 tons)
Year :
U.S. Va. N.C. Ga. Fila. Ala. Texas Okla.
1889 43.1 12.9 5.1. 8.7 5.0 3.9 0.6 —
18992 | 143.6 40.8 41.5 20.1 13.6 14.3 2.6 0.7
1909 177.0 49.3 60.8 15.8 4.9 19.5 13.2 0.4
1919 344.1 70.4 70.8 57.8 18.6 82.5 25.9 2.8
1929 449.1 78.8] 112.2 | 121.9 16.0 58.6 29.8 12.5
1939 606.1 89.5] 195.8 | 184.3 18.7 71.3 66.8 2.0
1940 883.3 | 107.8] 183.8] 301.1 34.2] 113.9 97.2 22.6
1941 737.6 84.8] 137.4] 234.8 28.9 | 126.0 79.9 18.9
1942 |1,096.4 85.1 169.4 | 333.9 32.8 | 167.7 | 208.8 60.0
1943 |1,088.3 85.5 | 153.8] 394.5 37.4 | 208.1} 140.3 26.0
1944 |1,040.4 90.9 | 177.0] 304.4 31.3 | 166.4] 153.0 42.3
1945 |1,021.1 74.7 152.0 361.1 33.0 170.5 161.3 43.9
1946 {1,019.2 95.6 | 136.4] 358.5 27.8 | 129.8] 197.8 58.6
1947 {1,094.0 99.6} 171.6) 390.4 32.8 | 146.9 | 186.4 75.6

® Total acreage and production for all areas
b Only 17 acres reported

14 THE PEANUT—THE UNPREDICTABLE LEGUME

The per-capita consumption of peanuts has just about doubled during
the past 20 years, and now amounts to more than 10 pounds per person.
Most of this increase has occurred since 1939 and is doubtless due in
some measure to extensive use by the armed forces during the war period,
though civilian use increased during the same period because of scarcity
of meat. However, during this same period an intensive advertising cam-
paign was carried on, stressing the food value of peanuts. This campaign
doubtless had considerable influence. An example of the information
used in this campaign is shown in table 4, where the nutritive value of

Table 4.—NUTRITIVE VALUE OF ONE PouND OF SELECTED Foops As PURCHASED.

Beef Pork
Roasted| Beans
Item Unit Peanut in |\common| Beans Rib | Round | Fresh
butter | shell or - lima® | roast | steak ham
kidney* rolled
Refuse..... Percent 0 28 0 0 0 11 14
Food
energy...| Calories | 2,808 | 1,961 | 1,588 | 1,548 | 1,252 789 | 1,326
Protein....| Grams 118.5 | 88.0] 99.9] 94.0 79.0 | 78.0} 59.3
Fate, oc cuss Grams 217.0 | 144.5 6.8 5.9 104 53 121
Carbo-
hydrates.|_ Grams 95.3 | 77.2 | 281.9 | 279.7 0 0 0
Calcium. . .|Milligrams 336 242 672 301 45 44 35
Phosphorus|Milligrams | 1,784 | 1,285 | 2,102 | 1,730 854 840 640
Iron.......|Milligrams 8.6 6.2] 46.8] 34.0; 11.8) 11.7 9.0
Vitamin A Z
value.... 1.U. 0 0 0 0 0 0 0
Thiamin. ..|Milligrams .89 .96 | 2.71 | 2.71 49 48] 3.75
Riboflavin |Milligrams .72 .52 1.07 1.07 1.07 .62 73
Niacin..... Milligrams] 73.5 | 53.0 9.6 9.6] 21.3 | 21.0} 16.0
Ascorbic
Acid... .|Milligrams 0 0 8 8 0 0 0
« Dry seed.

peanuts is compared with that of four other common foods (8). Con-
tinued publication of such information can be expected to have a decided
influence upon the demand for peanuts and encourages the hope that the
per-capita consumption of peanuts and peanut products may continue to
increase rather than recede to the former level.

Much money and effort have been expended upon development of
new ways of introducing peanuts into the diet, utilizing the whole peanut
or the defatted peanut flour ; but none of these new items has yet become
important commercially. The important channels for disappearance of
the edible peanut stocks are shown in figure 4.

ECONOMIC IMPORTANCE OF PEANUTS 15

OER

WIR
Hs

wo
fi
x

Figure 4.—Important uses of edible peanut stocks.

Peanut butter now accounts for disappearance of more than 50 percent
of our edible stock. Of the 1947 crop, nearly 325 million pounds were
utilized in peanut butter. This was 56 percent of the shelled edible stock
retained for domestic use. At present considerable research is being di-
rected toward improving the quality of peanut butter, and there are indi-
cations that consumption will continue to increase.

SELECTED REFERENCES
(1) ANon.

1947. WORLD PEANUT PRODUCTION EXCEEDS PREWAR OUTPUT. Foreign Crops
and Markets. (mimeo.) 55 (22):371-373. U.S. Dept. Agr.

(2) ———
1948. PEANUT STOCKS AND PROCESSING REPORT. U.S. Dept. Agr. Weekly
Peanut Report. (mimeo.) 30 (51) :3-4.
(3) ———
1789. GENERAL EXPORTS FROM THE PORT OF CHARLESTON, S. C., FROM NOVEM-
BER 1786 TO NOVEMBER 1787. The American Museum or Repository.
5:253. Philadelphia.
(4) ———
1848. GROUND PEAS. Southern Cultivator 6:40.
(5s) ———

1859. CULTIVATION OF THE PEANUT. Southern Cultivator 17 (3):79.

16 THE PEANUT—THE UNPREDICTABLE LEGUME

(6) ANON. -
1874. AGRICULTURAL STATISTICS. Ga. State Agr. Soc., Proc. 46:64. August.
(7)
1904. PEANUTS FROM VIRGINIA FOR UNCLE SAM AND THE WORLD. 8 p. booklet
published by Gwaltney-Bunkley Co.
(8)

1945. TABLES OF FOOD COMPOSITION. U.S. Dept. Agr. Misc. Pub. 572:1-30.
(9) Burke, Emizy P.
1850. REMINISCENCES OF GEORGIA, vili + 252 pp. James M. Fitch, Ohio.
(Peanuts p. 126)
(10) CHEVALIER, AuG.
1934, MONOGRAPHIE DE L’ARACHIDE CH. vil. Rev. Bot. Appl. & Agr. Tropical
14 (158) :833-864. (see p. 840)
(11)

1933. MONOGRAPHIE DE L’ARACHIDE. VI HISTOIRE DES EMPLOYS DE L’ARACHIDE,
Rev. Bot. Appl. and Agr. Tropical 13 (147) :747-752.
(12) Corton, H. E.
1872. ABOUT PEANUTS AND PEANUT OIL. Rural Carolinian 3:428-429,
(13) Dent, JonN H.
1850. LETTER TO DIRECTOR OF PATENT OFFICE. Patent Office Rpt. 1849:
148-149,
(14) DuTeERTRE, R. P. J. B.
1667. HISTOIRE GENERAL DES ANTILLES. (ref. p. 121)
(15) Eassy, W. B.
1851. LETTER TO COMMISSIONER OF PATENTS. Rpt. Com. Patents 1851 (2):
353-355.
(16) FisHer, W. H.
1946, PEANUTS IN THE FIFTH FEDERAL RESERVE DISTRICT. Research Dept.
Fed. Res. Bank of Richmond, x + 139 pp. Richmond.
(17) Gasso, J. G. C.
1855. THE PEANUT, OR PINDAR. Rpt. Com. Patents 1855:259.
(18) JEFFERSON, THOMAS.
1904. NOTES ON THE STATE OF VIRGINIA. Works of Thomas Jefferson (Federal
Edition by Thomas Ford) 3:408. G. P. Putnam’s Sons.
(19) JossELYN.
1924. NEW ENGLAND'S RARITIES DISCOVERED. (reprinted in) Archaelogia
Americana 4:121-122.
(20)

1924, DESCRIPTION OF THE NOW DISCOVERED RIVER AND COUNTRY OF VIRGINIA
(reprinted in) Archaelogia Americana 4:60-61.
(21) MacC Lenny, W. E.
1935. HISTORY OF THE PEANUT. Suffolk News Herald. Jan. 18, 1935.
(22) PAULETTE, J. C.
1848. CULTURE OF THE GROUND PEA. Southern Cultivator 6 (3) :53-54.
(23) Puitips, M. W.
1852. LETTER TO COMMISSIONER OF PATENTS. Rpt. Com. Patents. 1852:65-67.
(24) Ramsey, Davip
1809. THE HISTORY OF SOUTH CAROLINA. David Longworth, Charleston.

ECONOMIC IMPORTANCE OF PEANUTS 17

(25) Sessions, L. H.

1942. THE PROBLEMS OF THE PEANUT BUTTER INDUSTRY. National Peanut
Council Yearbook, 1942 :29-32.
(26) Urt, C. A. A. ‘

1914. SOME DATA ON PEANUT BUTTER. Jour. Ind. & Eng. Chem. 6 (9) :746-747.
(27) Watson, Str WILLIAM

1769. SOME ACCOUNT OF AN OIL, TRANSMITTED BY GEORGE BROWNRIGG OF

NORTH CAROLINA. Phil. Trans. Roy. Soc. London. 59:379-383.

(28) WiILLiaMs, JoHN LEE.

1837, TERRITORY OF FLORIDA. 112 pp. A. L. Goodrich, New York.
(29) Winton, A. L.

1899. PEANUT BUTTER AND PEANOLIA. Conn. Expt. Sta. Rpt. 23:138.

CHAPTER II

ORIGIN AND EARLY HISTORY
OF THE PEANUT

B. B. HIGGINS’

What are the origin and the history of the cultivated peanut, and what
are its close relatives in the plant world? One would think that a plant
with such striking botanical characteristics and with such economic possi-
bilities could not long escape notice of botanists or of those interested in
production of food crops, and that these questions would be readily answer-
able. However, the New World presented to the eyes of explorers and
colonists so many new plants: Indian corn, Irish potato, sweet potato,
cassava, cacao, beans, tobacco and many other plants of even greater
interest that the peanut received scant attention. Consequently, the origin,
history, introduction into various countries, and the affinities of the culti-
vated peanut are still hazy. Many points have been cleared during the
past 25 years and with the accelerated investigations now in progress
much more information should be available within a decade.

In 1933, August Chevalier (6) wrote, “Je probleme de le origine de
Vv Arachide a fait couler des flots d’encre.” (Translation: The problem of
the origin of the peanut has made floods of ink flow.) During the nine-
teenth century a number of authors attempted to prove that the peanut
originated in Africa and cited plants with subterranean fruits described by
Theophrastus and Pliny as occurring in Egypt and other Mediterranean
countries. Chevalier (6) has summarized the opinions of various students
as to the identity of these plants and the evidence is conclusive that neither
Pliny nor Theophrastus saw or mentioned the plant now known as
Arachis hypogaea. The Arachidna of the ancient Greeks was evidently
applied to a species of Lathyrus, Arakos referred to Lathyrus tuberosa,
the Ouiggon mentioned by Theophrastus as occurring in Egypt was

1B. B. Higgins is botanist, Georgia Agricultural Experiment Station.

ORIGIN AND EARLY HISTORY OF THE PEANUT 19

Calocassia antiquorum, and the Oetium of Pliny referred to Cyperus
esculentus. Arachis hypogaea was introduced into Egypt only in recent
times as indicated by the vernacular name “ful sudani.”” The confusion
was accentuated by the fact that the name Arachidna was used for the
peanut by several naturalists and voyagers near the close of the seven-
teenth century. ‘

Likewise, there is nothing to support the suggestion of Asiatic origin.
Tradition in China and in India indicates recent introduction into the
Asiatic mainland from the Philippine Islands or other of the South Pacific
Islands.

Many attempts have been made to trace the distribution of the peanut
through the vernacular names which might have been passed from one
locality to another with seed of the plant. Chevalier (7) lists several hun-
dred but, with few exceptions, these are local names which in that dialect
are more or less descriptive of the seed or fruits of the plant as, for ex-
ample, the English names, peanut, groundnut, and groundpea ; the French,
“pistach du terre,” (ground pistache) ; and the Portuguese, ‘““Amendoim.”
Exceptions to be cited such as “pindar” and “goober” are undoubtedly
corruptions from some African names by African-born slaves who had
known either the peanut or Voandzeia in Africa. The two common names
in use in Spanish-speaking countries are: ‘“Cacahuate,” used in Spain
and Mexico, derived from the Nahuatlan (Aztec) name “‘tlalcacahuatl”
(earth cacao) ; and the other, “mani” used throughout Spanish America
except Mexico, is Thalail name heard by the Spaniards in Hispanola,
now Haiti-Santo Domingo. The Brazilian name ‘‘Mandubi” is apparently
derived from the Indian name which is variously written from the Indian
articulation as “Mandobi,” “Manobi,” “Mun dubi,” “Mondorvi” and
“Minui.”

In 1838, Bentham published his “Flora Braziliensis” describing five
species of Arachis, all from Brazil. This caused botanists generally to take
with favor the claim for American origin of the cultivated 4. hypogaea L.
because, as stated by A. de Candolle (4), “A genus with all its known
species thus confined to a single region of America can hardly have a
species common to both the New World and the Old. That would be too
great an exception to a common principle of phytogeography.” But posi-
tive proof as to American origin came with the discovery of peanuts,
similar in appearance to varieties now grown in Peru, in ancient graves
excavated at Ancon, Pachacamac, and other points in the desert region
along the coast of Peru, about 1875. E. G. Squier (21), a United States
Commissioner to Peru, gives a vivid description of these burial grounds:

20 THE PEANUT—THE UNPREDICTABLE LEGUME

“During my residence in Lima, I visited the ruins of Pachacamac, twenty
miles south of the capital... . Pachacamac is one of the most notable spots
in Peru, for here, as we are told by the old chroniclers, was the sacred
city of the natives of the coast before their conquest by the Incas....In
Pachacamac, the ground around the temple seems to have been a vast
cemetery. Dig almost.anywhere in the dry nitrous sand, you will come
upon what are loosely called mummies, but which are the desiccated
bodies of the ancient dead. ... I will record what I found in a single tomb,
which will illustrate how a family, not rich, nor yet the poorest, lived in
Pachacamac.... Besides the bodies there were a number of utensils, and
other articles in the vault; among them half a dozen earthen jars, pans
and pots of various sizes and ordinary form. One or two were still in-
crusted with the soot of the fires over which they had been used. Every
one contained something. One was filled with groundnuts familiar to us
as peanuts.” Since the coast tribes occupied this region before develop-
ment of the Incan Empire, some archaeologists consider these graves as
possibly antedating our Christian era, but overlapping of the various
culture periods of the area makes dating of the graves uncertain. There
can, however, be no doubt that they are very ancient, certainly pre-
Columbian.

Monardes (16), who lived in Peru about 1550, described briefly the
subterranean fruits without giving a name for the plant. He said it was
grown along the Maranon River and was highly esteemed by both
Indians and Spaniards. -

Garcillosa de la Vega, son of an Incan princess and a Spanish father
and born in Peru in 1539, published in 1609 his “Los Commentaries
Reales” in which mention is made of ‘“‘ynchic” as an important food of the
Incas.

Thus, Peru has become conspicuously associated with the peanut,
and development of the cultivated forms is frequently cited as one of the
accomplishments of the Incas; but continued study of old manuscripts
has shown that cultivation of the peanut was by no means confined to
Peru and Brazil at the time Columbus visited the New World. It is of
interest in this connection to remember that the two common names for
the plant in Spanish-speaking countries, ‘mani’ and “cacahuate,” are of
North American origin.

Las Casas (5), a priest who lived in “New Spain” (now Haiti-Santo
Domingo) from 1510-1530, mentioned “mani” among the food plants
being grown by a tribe of Indians on the island. Likewise Oviedo (17),
the official historian of “New Spain” 1513-1524, mentioned “mani” as

ORIGIN AND EARLY HISTORY OF THE PEANUT 21

one of the important food plants very commonly grown by the Indians of
“New Spain” and other islands of the West Indies. The complete record
follows: “Del mani, que es cierto genero de fructa e mantenimiento
ordinario que tienen los indios en esta Isla Espanola e otras islas destas
Indias.

“Una fructa que tienen los indios en esta Isla Espanola, que llamen
mani, la qual ellos siembran, e cogen, e les es muy ordinaria planta en
sus huertos y heredades, y es tamana como pinones con cascara, e tienenla
ellos por sana: los chripstianos poco caso hacen della, si no son algunos
hombres baxos, 0 muchachos y eschlavos, o gente que no perdona su
gusto a cosa alguna. Es de mediocre sabor e de poca substancia e muy
ordinaria legumbre a los indios, e hayla en gran cantidad.” (Translation:
“Of the peanut, which is a certain kind of fruit in common use by the
Indians in this Isla Espanola and other islands of the Indies. A fruit
which the Indians in this Isla Espanola have, they call mani (peanut)
and they plant it, and harvest it and it is a common plant in their gardens
and fields, and it is the size of a pine nut with a shell, and they think it is
healthful ; the Christians pay little attention to it, unless they are common
people, or children, or slaves, or people who do not have a fine taste. It
is of mediocre taste, and little substance, and is a very common food of the
Indians who use it in quantity.”)

About the same time (1518-1521) Cortes conquered Mexico and this
was quickly followed by exploration and colonization. Many voluminous
reports on the natural resources of the country and on the Aztec civiliza-
tion and customs were sent to the king of Spain. Few of these early docu-
ments have been available for study and no clear-cut picture of the cul-
ture and use of peanuts by the Indians of Mexico-has been obtained. In
reporting on medical practice among the Aztecs, Sahagun (19), historian
and instructor in a mission school at Tlatalalco, 1529-1590, mentioned use
of tlalcacauatl (Nahuatlan name for peanut, from tlatle = earth and
cacauatl = cacao seed) as a poultice for swollen gums; but he did not list
it under this name among the plants used for food.

Jean de Leary (15), who lived at Rio de Janeiro about 1555, pub-
lished a description of the fruits under the Brazilian Indian name
“manobi.” According to Filcalho (11), it was again noted in Brazil in
1570 by Gabriel Soares de Souza, and again in Peru about the same time
(1571) by Joseph de Acosta (1).

During the next 200 years the plant was described or mentioned by
many botanists and explorers in the New World, and by botanists in
Europe; but it was not until about 100 years ago that the range of the

22 THE PEANUT—THE UNPREDICTABLE LEGUME

wild species began to be extended beyond the borders of Brazil. Since
then the wild species have been found abundantly distributed from the
Amazon River through Brazil, Bolivia, Paraguay, Uruguay and northern
Argentina to about 35° south latitude. The wild species of Arachis form
an important part of the herbage for supporting the vast herds of cattle in
this region. Some species seem especially adapted to growth and survival
in hard clay soils and under conditions of close grazing. Others occur
mostly in loose-textured sandy or alluvial soil. The cultivated forms are
even more widely distributed and appear to be especially numerous and
diverse in northern Argentina. E. C. Clos (9), in 1939, published on the
types of cultivated peanuts, apparently indigenous to Argentina. He as-
sembled 46 collections, including those grown commercially as well as
those grown by various groups of Indians. These were grown and
grouped according to characteristics such as: Vine type, bunch or
runner ; pod size and shape; size and number of seed; and color of seed
coat, black, red, flesh, white, and white with red splotches. The 46
strains appeared to be quite homogenous and fell into 15 distinct classes.

There is considerable evidence indicating that the cultivated forms of
the peanut originated in the Gran Chaco area including the valleys of the
Paraguay and Parana rivers, and were at an early date distributed
throughout the tropical and subtropical regions of both South and North
America.

The various Indian tribes were not so isolated as one might suppose.
In this connection, it is of interest to remember the Incan legend that they
came to Peru from the South; also that the Incan Empire included a
part of northern Argentina well east of the Andes. Archaeologists and
ethnologists are convinced that a great influx of South American Indians
came to Central America in a pre-Maya era. Central American Indians
told the Spaniards of the fabulously wealthy Incas in Peru and of the
great cities of the Aztecs in Mexico. Apparently there were regular trade
routes between the Aztecs and the pueblo-dwelling tribes in what is now
New Mexico. Archaeologists (13) also find evidence of communication
between the Indians of the West Indies and those of the entire Gulf
Coast.

It is not unbelievable, therefore, that the peanut was carried by the
Indians to most areas suited to its culture, just as they spread corn,
bean, pumpkin, cassava, sweet potato, and Irish potato.

How can we account for rapid establishment of peanut culture in other
portions of the world, particularly in Africa and in Asia?

Chevalier (6) reviewed the argument of Brown, Ficalho, and Wiener

ORIGIN AND EARLY HISTORY OF THE PEANUT 23

supporting the contention that Arachis hypogaea was indigenous in
Africa, and concluded that there is absolutely no proof of the presence of
this plant in Africa in pre-Columbian times. Continuing, he says that
after 1502 communication between the west coast of Africa and Brazil
Cwas frequent. Portuguese ships going to Brazil always touched the
African coast to take on fresh water and food, and the return trip was
made by the same route. Naturally, having established colonies and trad-
ing posts on both coasts, the products of each were introduced to the
other country. They introduced the African Voandzeia subterranea into
Brazil where it was grown to some extent under the name “Mandubi de
Angola.” Pedro Alvares Calval, sailing for India with a large fleet, swung
too far west and touched the Brazilian coast on April 22, 1500. He took
possession of the land in the name of Portugal, then sailed on around the
Cape of Good Hope to the East Indies. After this time, the Portuguese
were very active in exploration and establishment of trading posts in
Brazil, in Africa, and in the East Indies. Apparently they introduced
maize, cassava, tobacco, and peanuts to the coasts of Africa. All four
spread so rapidly that travelers in Africa a hundred years later thought
all indigenous to Africa. It seems likely that the Portuguese introduced
the plants at many points along the African coast, since they had already
established small colonies and trading posts even along the east coast of
Africa prior to 1522, when Juan Sebastian del Cano, in command of the
“Vittoria” in the final lap of Magellan’s voyage around the world, feared
to put in at any point along the African coast, although many men of his
crew were dying of starvation; because he feared interception by
Portuguese.

Both Portuguese and Spaniards probably carried peanuts to the East
Indies during the early years of the sixteenth century. Waldron (23) and
others have suggested that the peanut was carried to the Philippines and
the Moluccas by Magellan on his circumnavigation trip, but this seems
hardly probable. According to Pigafetta’s (18) account, Magellan’s fleet
wintered at Port St. Julian, southern Patagonia, and the following spring
passed through the Strait of Magellan and then sailed west-northwest
for 3 months and 20 days without seeing land. He did not touch Peru as
suggested by Badami (3). Since his crew was reduced to eating rats,
sawdust, and leather from the ship’s rigging, they certainly would have
eaten any peanuts that were aboard. Furthermore, Pigafetta does not
mention any seed or any agricultural products among the articles traded
or presented to the islanders. He did mention that Chinese trading vessels

\ visited the islands during Magellan’s stay. After Spanish colonization of

24 THE PEANUT—THE UNPREDICTABLE LEGUME

the Philippine Islands, the islands were governed from Mexico and a
regular trade route was established between them and the west coast of
Mexico, and it would seem likely that peanuts were carried there from
Mexico.

The statement that the peanut was not known in North America until
introduced on slave ships from Africa has been made so frequently that
we have accepted it as true, in spite of the evidence that it was being
grown in Mexico and Central America (12, 19, 23) as well as in various
islands of the West Indies before the arrival of Europeans. This state-
ment was based upon a single paragraph in which Hans Sloane (20), in
his natural history of Jamaica, mentioned peanuts grown by Mr. Harri-
son from “Guinea seed” and ignores the fact that he mentioned other
collections. The first reference to the plant is in Volume I, pages 72 and
73, under the paragraph heading : ““Arachidna Indiae utriusquetetraphylla
Par. Bot. pr. p. 314.” Then follows the synonomy with 36 references and
ends with the statement: ‘In Caribearum Insularum una hanc plantam
collegi, sed qua non memini.” (Translation: I collected this plant on one
of the Islands of the Caribbean, but which (one) I do not remember. )

On page 184 we find the commonly noted reference: “XXII.
Arachidna Indiae utriusquetetraphylla. Par. Bot. pr. cat. p. 72. Mandobi
fructus pisonis Mus. Swammerd. p. 15. An Terfez. Ogilb, Africa p. 22.
I found this planted from Guinea seed, by Mr. Harrison, in his Garden
in Liguanee. The fruit, which are called by seamen earthnuts, are brought
from Guinea in Negro ships, to feed the Negroes withal in their voyage
from Guinea to Jamaica. . . . An oil is drawn out of them by expression,
as good as that of almonds. . . . This is the nut Clusius speaks of,
wherewith the Portuguese victual their slaves to be carried from St.
Thome to Lisbon.”

Reference is also made in Volume II, page 369: “Mandubi quadri-
folium Americanum fructus subterraneous flore luteo Amenduinas
Lusitanorum. Surian. An Junsa Linchot. cap. 8, or cap 6, C.B. Pin. 346?
Arachidna quadrifolia vellosa flore luteo. Plum. pl. Amer. p. 49. Pasta-
ches des Isles, autrement Manobi Labat. T. 4 p. 49. Mr. Barham says, in
his observations, they are eaten raw, roasted, or boiled and never occa-
sion any headache.”

There are other incidental references, but each of these three notes
evidently refers to different collections and indicates clearly that peanuts
were commonly grown in the islands visited by Sloane, and probably of
more than one type. It seems probable that he mentioned the peanut

ORIGIN AND EARLY HISTORY OF THE PEANUT 25

grown by Mr. Harrison from “Guinea seed” because it differed from
those commonly found in the Caribbean Islands.

Du Tertre (10) gave a very good description of the peanut plants so
that one can easily recognize the runner type, pods with two or three
seed with red seedcoats. This same type of peanut was also observed by
Labat (14) and described as apparently a wild plant on Guadeloupe in
1697.

Apparently the Indians of the West Indies and those of the Florida
mainland had occasional contacts and in this way the Florida Indians
probably obtained the peanut. However, proof of the pre-Columbian
presence of peanuts in either Florida or the Texas-New Mexico area has
not yet been found.

The records found to date are not clear as to the origin of the various
types grown in the United States. Several authors mentioned importa-
tion, for the New York market, of peanuts from Africa; and the small-
seeded runner, known successively as African, Wilmington Runner,
North Carolina Runner, Georgia Runner, Southeastern Runner, etc.,
very probably came from Africa. The Spanish variety was imported
from Spain in 1871 (2). Valencia was probably received from the same
source. The origins of the Virginia type, the Tennessee Red, and the
Tennessee White are still uncertain. The two latter resemble closely the
peanuts most commonly grown in Mexico and Central America. Che-
valier (8) described 4. hypogaea L. var. macrocarpa A. Chev. to include
Jumbo, Virginia Runner, Virginia Bunch and Samatiga, with Jumbo as
the type. He states further that Jumbo originated at Bahia, Brazil, but
failed to indicate the authority for this statement. Jumbo, as known in the
United States, is not a variety distinguishable from Virginia Runner and
Virginia Bunch. It should be thought of as a large-seeded strain of
either Virginia Runner or Virginia Bunch and considered as a market
classification rather than a variety of peanuts.

SELECTED REFERENCES

(1) Acosta, JOSE DE.
1571. HISTORIA NATURAL Y MORAL DE LAS INDIAS.
(2) ANON.
1898. JOURNAL OF COMMERCE (NORFOLK, VIRGINIA). November 5.
(3) Bapami, V. K.
1935. ARACHIS HYPOGAEA LINN. GROUNDNUT OR PEANUT. ORIGINAL HABITAT
AND ITS DISTRIBUTION IN THE WORLD. Jour. Mysore Agr. and Exp.
Union 15 (4) :141-154,

26 THE PEANUT—THE UNPREDICTABLE LEGUME

(4) CANDOLLE, ALPHONSE DE.
1882. L’ORIGINE DES PLANTS CULTIVEES.
(5) Casas, BARTOLOME DE LAS,
1909. APOLOGETIC HISTORIA DE LAS INDIAS. Serrano y Sanz ed. Madrid,
(‘“Mani” p. 29).
(6) CHEVALIER, AUG.
1933, HISTOIRE DE L’ARACHIDE. Rev. Bot. Appl. & d’Agr. Trop. 13 (146 &
147) :722-752.

(7)
1933. NOMS VERNACULAR DE L’ARACHIDE DANS LES DIFFERENTS PAYS. Rev.
Bot. Appl. & d’Agr. Trop. 13 (146 & 147) :740-747,

(8)

1933. LE GENRE ARACHIS ET SA SYSTEMATIQUE. Rev. Bot. Appl. & d’Agr.
Trop. 13:753-789.
(9) Cros, E. C.
1939, LOS TIPOS DE MANI CULTIVADOS EN LA ARGENTINA Y SU DISTRIBUCION™
GEOGRAPHICA. Phisis 18:317-329.
(10) Du Tertre, R. P. J. B.
1667. HISTOIRE GENERAL DES ANTILLES. (ref. p. 121)
(11) FItcaLHo, DE
1884. PLANTAS UTEIS DE AFRICA PORTUGUEZA. Lisbon.
(12) Grecory, C. V.
1929. FARMING THROUGH THE AGES. FIRST FARMERS OF AMERICA. Prairie
Farmer 101:77, January 19, 1929.
(13) Kriecer, H. W.
1931. ABORIGINAL INDIAN POTTERY OF THE DOMINICAN REPUBLIC. U.S. Nat.
Mus. Bul. 156, 165 p.
(14) Lagat, R. P.
1742.VOYAGE AUX ILES D’AMERIQUE. 4:365-369.
(15) Leary, JEAN DE.
1578. HISTOIRE D’UN VOYAGE FAIT EN LA TERRE DU BRESIL, AUTREMENT DIT
AMERIQUE. La Rochelle.
(16) Monarpes, N.
1574. DE SIMPLICIBUS MEDICAMENTIS EX OCCIDENTALI INDIA DELATIS, QUORUM
IN MEDICINA USES EST. 88 p.
(17) OvrEDO Y VALDES, GONZALO FERNANDEZ DE.
1944-45. HISTORIA GENERAL Y NATURAL DE LAS INDIAS. 14 vols. Asuncion,
Paraguay. (ref. Vol. 2:176)
(18) PrGaFETTA, ANTONIO.
PRIMO VIAGGIO INTORNO AL MONDO. IN BLAIR AND ROBERTSON. The
Philippine Islands, Vol. 33.
(19) SAHAGUN, BERNADINO DE.
1946. HISTORIA GENERAL DE LAS COSAS DE NUEVA ESPANA. 3 Vols. Mexico.
(ref. Vol. 2:262-263.)
(20) SLoANE, Hans,
1698. CATALOGUS PLANTARUM QUOQUE IN INSULA JAMAICA SPONTE PROVE-
NIUNT, VEL VULGO COLUNTUR, ETC. D. Brown, Temple Bar. London.

ORIIGIN AND EARLY HISTORY OF THE PEANUT 27

(21) Squigr, E. G.
1877, PERU; INCIDENTS OF TRAVEL AND EXPLORATION IN THE LAND OF THE
incas. New York.
(22) VERRILL, ALPHEUS.
1937. THE MIGHTY PEANUT. Foods America gave the world. Vol. 1, p. 95-100.
(23) Wavpron, R. A.
1919, THE PEANUT (ARACHIS HYPOGAEA)—ITS HISTORY, HISTOLOGY AND
uTILiITy. Contr. Bot. Lab. Univ. Penna. 4:301-333.

CHAPTER III

MORPHOLOGY, GENETICS AND
BREEDING

WALTON C. GREGORY, BEN W. SMITH AND
JOHN A. YARBROUGH’

Beginning with Oviedo’s (47) account of the West Indies published in
1535 and Schmidel’s (64) description of his travels in the La Plata Basin
during the years 1534 to 1554, the reader of the peanut literature is con-
fronted with works in Japanese, Chinese, Dutch, Danish, German,
French, Bulgarian, Russian, Italian, Spanish, Portugese, and English.
Here and there, keen observers have recorded their findings regarding the
structure and development of the peanut plant, only to have them buried
in the passage of time by an accumulation of inaccuracy and trivia.
These inaccuracies have been doubly impressed upon the writers
who find that the 77 titles listed at the end of this chapter omit little
indeed of the information contained in the 700-800 references at their
disposal.

Prior to 1949 we have found only a single description (which was
wrong!) of the morphology and development of the seed and seedling,
only two inadequate descriptions of the internal reproductive morphology
of the peanut, and only a few correct accounts of the relationship between
the aerial flower and the subterranean fruit. In 1569 Monardes (45) was
so confused by the subterranean occurrence of peanut fruits that he
failed to associate these with the plant at all! A century later Marggraf
(43) illustrated the fruits as growing on the roots! The first accurate
description of the peanut Hower was published by Poiteau (52) in 1806
and confirmed by Richard in 1823 (58), but Bentham’s (10) erroneous

1 Walton C. Gregory is Professor of Agronomy, North Carolina State College, Ben W. Smith is

Associate Professor of Agronomy, North Carolina State College, and John A. Yarborough is
Professor of Biology, Meredith College.
28

MORPHOLOGY, GENETICS AND BREEDING 29

interpretations of 1839 are still to be found in many recent textbooks.

Beginning with a consideration of the peanut seed and seedling and
passing to the mature root, stem and leaf, this chapter then deals with
the reproductive morphology of the plant and concludes with a discus-
sion of its genetics and breeding. Without attempting to cite all the
known references which have some bearing on the topics discussed, the
writers have attempted to cover the topics themselves with as much
thoroughness as existing knowledge permits. This chapter does not in
any sense represent a botanical or genetic monograph on the genus
Arachis but does summarize botanical and genetic information as it re-
lates to a single species of the genus. It is our purpose to present the
status of knowledge on peanut morphology, reproduction, variation, and
breeding.

SEED AND SEEDLING

Outstanding features of the seeds of cultivated peanuts are their
variable sizes, colors, and shapes. They may be red, white, purple, pink,
flesh, rose, tan, light brown, or even red and white. The actual range of
seed size in peanuts is probably unknown, but we have seen and planted
seed ranging from 0.2 of a gram to 10 times that size. Seeds may be
almost spherical, elliptical or much elongated.

Each seed is composed of two massive seed leaves (cotyledons), upper
stem axis and young foliage leaves (epicotyl), and lower stem axis and
primary root (radicle). A thin papery seed coat covers the seed (figure
1). In contrast to most papilionaceous legumes the axis of the embryo
proper is straight. All of the leaves and above-ground parts which the
seedling will have for the first 2 to 3 weeks of growth are already present
in the dormant seed. The epicoty] consists of three buds, one terminal and
two cotyledonary laterals. In the terminal bud there are four foliage
leaves and in the cotyledonary laterals one or two leaves. Thus the dor-
mant embryo has from six to eight differentiated leaves, all of them
ready to expand and go to work immediately upon germination (76).

When peanut seeds are put to germinate at 80°F. the radicle appears
after 24-36 hours. Reporting from Senegal, Bouffil (13) stated that
hardly 2 days elapse before the appearance of the radicle. In Germany
Richter (59) found that 8 to 10 days were required for germination in
damp sphagnum in the hothouse. In outdoor plots at Raleigh, North
Carolina, 8 to 10 days were required for emergence. Discrepancy be-
tween the appearance of the young root (24 to 48 hours) and the ap-
pearance of the shoot (8 to 10 days) is caused by a striking difference in

30 THE PEANUT—THE UNPREDICTABLE LEGUME

the initial growth between shoot and root. The root grows very rapidly,
reaching a mean length of 46 mm. in 4 days (Bouffil, 13) and 100 to 400
mm. in 4 to 5 days (Yarbrough, 76). During the first 2 days of this rapid
root growth no lateral roots develop (figure 2). But by the time the

Figure 1—Mature peanut seed. One cotyledon has been removed to show the
straight embryo with its well developed epicotyl and massive radicle. The papery
seed coat is visible around the edge of the cotyledon.

seedling is 4 to 5 days old, 25 to 50 lateral roots have appeared (Yar-
brough, 77). Figure 3 shows the hypocotyledonary axis grown to a
length of 164 mm. while the entire epicotyl has not exceeded the length of
the cotyledons, about 20 mm.; in other words, an epicotyl-hypocotyl
ratio of %. In 11% days this root system reaches a length of 30 cm. and
produces 100 to 116 laterals (figure 10). Meanwhile the shoot expands

MORPHOLOGY, GENETICS AND BREEDING 31

Figure 2.—Peanut seedling, 2 days old. The well defined collar below the smooth
hypocotyl marks the region of transition from root to stem. Lateral roots are
absent and soil particles cling to the roughened surface of the primary root.
(after Yarbrough, 76.)

32 THE PEANUT—THE UNPREDICTABLE LEGUME

Figure 3.—Peanut seedling, five and one-half days old. The epicotyl barely exceeds
the cotyledons but hypocotyl and primary root have a total length of 164 mm.
Note the distinct collar at the transition region and the belated appearance of
lateral roots. (after Yarbrough, 76.)

% MORPHOLOGY, GENETICS AND BREEDING 33

the foliage leaves laid down in the seed, but no new growth is visible
until about 21 days after planting.

ROOT

In a young peanut seedling the root is sharply differentiated from the
hypocotyl by an abrupt constriction (figures 2 and 3). This constric-
tion or collar marks precisely the transition zone (59, 76). Just at this
collar the intact epidermis of the hypocotyl gives way to the non-epi-
dermal outer layers of the primary root. Even superficial examination
reveals the fact that no true epidermis exists on the peanut root. Figure
2 shows the soil clinging to the broken, sloughing surface. This condition
in peanut roots, and its expected morphological corollary, the absence of
root hairs, have been observed by Pettit (50) and Richter (59). Richter
suggested that the ragged, uneven surface of peanut roots, where the
root hairs would normally be expected to occur, served as an active ab-
sorptive surface. Waldron (75) reported root hairs on peanuts and
showed that under ordinary conditions they usuallytappeared as rosettes
of hairs at the junctions of the lateral and main roots, but Reed (55) re-
ported that few hairs occurred under field conditions. The internal de-
velopment and differentiation of tissues in the peanut root were first
touched upon by Richter in 1899. Yarbrough (76) has recently published
a description.of their internal development. .

A longitudinal section through the growing tip of a young root
shows the root cap, root initials, stele, and cortex. Among the root initials
there is no specific differentiation into initiating layers. The root cap,
cortex, and stele are laid down by the initials most proximal to these
areas by appropriate longitudinal, tangential, or radial divisions. —

The absence of epidermal initials ultimately results in the absence of
an intact epidermis and, consequently, the almost complete lack of root
hairs. The cross section in figure 4 shows that outside the cortex there
is a cork cambium-like region which by both radial and tangential cell
divisions lays down the closely packed absorbing cells which Richter be-
lieved substituted for root hairs as absorbing surfaces. The sloughing ex-
ternal cells are thus continually supplied from within. This region of the
root extends only 8 to 10 mm. back from the root cap and has been shown
to be an actively absorbing region in dye absorption studies by both
Richter and Yarbrough. Yarbrough emphasizes the probability that the
importance of this region.in absorption is confined to mineral ions, a fact
of considerable significance when one considers the ultimate position of
such maristems in the mature root system. With respect to the limited

34 THE PEANUT—THE UNPREDICTABLE LEGUME

occurrence of root hairs, Yarbrough’s results confirm those of Badami
(3) and Waldron (75) that both high temperature and high humidity
favor their production.

If one examines a cross section of the root (figure 4), it can be seen
that the innermost row of cortex cells constitutes a typical endodermis.

seul

ere:
pei
sent oh

eeerseas ae
HE

‘
re

CAH
reent
3

Figure 4.—Primary root of peanut seedling, cross section; s, stele; c, cortex; m,

meristematic zone; sl, sloughing outer cells. No epidermis is present on the
root. (after Yarbrough, 76.)

MORPHOLOGY, GENETICS AND BREEDING 35

The central cylinder of the primary root differentiates pericycle, phloem,
xylem, and pith in normal fashion. The phloem fibers occur in four
homogeneous bands. These mature about the same time or a little later
than the last primary xylem. Thus the primary vascular structure of the
root is tetrarch, external evidence of which can be seen in the 4-ranked
arrangement of the first lateral roots.

Weise 3

Figure 5.—Older primary root of peanut, cross section. Secondary wood has ap-
: peared; cortex and pith have begun to disintegrate. (after Yarbrough, 76.)

36 THE PEANUT—THE UNPREDICTABLE LEGUME

Yarbrough (76) -emphasizes the following characteristic features of
the root system in the yourig peanut seedling:

1. The central stele shows a tetrarch or four-pointed pattern of four
xylem groups with alternating phloem groups. This is the usual radial
arrangement of conducting tissue found in roots of all higher plants.

2. Although Compton (19) stated that the peanut root has no pith,
note the large pith in the center of the cross section shown in figure 4.
Old roots are quite woody and the pith breaks down, leaving the root
hollow.

3. Old roots have their internal structure modified by two meri-
stematic zones: (a) the cork cambium which develops from the pericycle
and causes the death and loss of all tissues external to it, and (b) the
vascular cambium which develops within the phloem and forms consid-
erable amounts of wood (figure 5).

4. Sparsely scattered hairs may be seen on peanut roots under con-
ditions of high temperature and high humidity with rosettes of hairs more
common at the bases of some lateral roots.

5. No true epidermis exists on peanut roots.

TRANSITION FROM ROOT TO STEM

The hypocotyl, that portion of the peanut stem below the cotyledons
and above the root, never emerges from the soil and thus becomes part
of the anchoring root system of the plant. The transition from root to
hypocotyl, however, is marked and abrupt, both internally and externally.
The transition from radial to collateral bundles was described by Richter
(59), by Compton (19) and by Yarbrough (76). According to Yar-
brough, “. . . there are four exarch xylem groups in the upper primary
root; just below the collar there are eight endarch groups formed by
division of each original one; in the collar or slightly above some fusions
may reduce the xylem groups to seven, six, or even four ; above this level
and throughout the hypocotyl further branching and anastomosing cause
the number of xylem groups to vary from nine to eighteen.” The four
phloem groups of the primary root pass through the zone of xylem
transition without modification but finally divide and with the associ-
ated xylem give rise to the collateral bundles of the hypocotyl. Externally,
at the collar the smooth, intact epidermis of the hypocotyl gives way to
the sloughing outer surface of the root. Internally, special tannin cells are
associated with collateral strands throughout the stem and in leaves,
flowers, and fruits. These disappear abruptly at the collar. Thus the
transition zone from root to stem is defined by:

MORPHOLOGY, GENETICS AND BREEDING 37

1, The abrupt out-swelling of the collar.

2. The sudden appearance of the intact epidermis of the hypocotyl at
the collar.

3. The transition from radial to collateral arrangement of the vascular
strands.

4. The immediate appearance of tannin cells associated with the col-
lateral bundles.

HYPOCOTYL

The hypocotyl in the seedling stage is very succulent, white, and
smooth. The central stele may be quite green even though the hypocoty] is

Figure 6—Young peanut hypocotyl, cross section midway. between’ collar and
cotyledons. Note the intact epidermis, wide cortex, stele with collateral vascular
traces, and central pith. (after Yarbrough, 76.)

38 THE PEANUT—THE UNPREDICTABLE LEGUME

always underground and the stele is surrounded by a fleshy cortex. In
the dormant seed most of the radicle is actually hypocotyl tissue and is
filled with stored food. During germination the hypocotyl, cortex, and
pith may serve as way-station, storage tissues for food moving out of the
cotyledons to the roots.

The hypocotyl, when cut transversely (figure 6), shows an intact epi-
dermis covered by a thin cuticle, a wide cortex where much stored food
may be found, and a central stele in which the conducting tissues, xylem
and phloem, are arranged on the collateral plan. The vascular bundles of
the hypocotyl increase to nine or more as compared to four in the root and
surround a large pith. As the hypocotyl becomes older (10 to 30 days) it
undergoes two significant changes, the first of which is a collapse of
epidermis and much of the cortex. The collapsing layer becomes soft and
may be easily rubbed off. Secondly, the collar at the base of the hypocotyl
becomes very woody and hard. The pith breaks down and the hypocotyl
ultimately becomes a hollow woody axis (76).

COTYLEDONS

The position of the cotyledons during germination determines whether
a seedling is classified as epigeal, i.e., with its cotyledons above the sur-
face of the ground as in the green bean or the soybean, or hypogeal as
in the case of the garden or English pea. In the first case the growth of
the hypocotyl pushes the cotyledons upward until they appear above the
surface of the soil. In the latter case the cotyledons remain just where
the seed was placed when planted. Peanuts do neither. The cotyledons
rise with the hypocotyl’ until the soil surface is reached and there they
stop. Bouffil (13) said that they were hypogeal; Yarbrough (76) said
that they were not epigeal. This growth of the hypocotyl which de-
termines the position of the cotyledons is a function of the depth of plant-
ing. Bouffil planted seeds of peanuts at depths of 3, 6, and 9 cm., and
found that the position of the planted seed determined the position of the
collar, and that the length of the hypocotyl was clearly related to depth
of planting. Yarbrough (76) has made a similar statement about hypo-
cotyl length. This fact is strikingly borne out in seedlings volunteering
in newly ploughed fields in the spring following a crop of peanuts the
previous summer. Many of these peanuts germinate on the plough sole
and sometimes must rise 12-14 cm. before reaching the surface. Under
these conditions the entire food supply from the cotyledons may be
exhausted and the young epicotyls emerge pale and yellow. When this
happens it has been consistently noted that with increasing depth of

MORPHOLOGY, GENETICS AND BREEDING 39

planting the hypocotyl length approaches a maximum of 10 to 12 cm. and
any further elongation necessary for emergence is made by the epicotyl.
This elongation of the epicotyl does not await attainment of maximum
hypocotyl length but appears to develop continuously in direct pro-
portion to depth of planting. It has likewise been observed that the length
of primary root varies inversely with planting depth to such an, extent
that peanuts germinating at their maximum depth for emergence are
almost devoid of roots. Bouffil illustrates this clearly in his photograph,
figure 1, page 10. At ordinary planting. depths the cotyledons (figure 7)
begin to shrivel (figure 8) as the foods leave them and go into the ex-
panding root and shoot systems. Twenty days after germination extreme
shrinkage (figure 9) is apparent.

oe ibe vy,

Figure 7—Cotyledon from 5-day old peanut seedling, cross section. The abundance

of stored food at this stage is revealed by the deeply stained cell contents. (after
Yarbrough, 76.)

40 THE PEANUT—THE UNPREDICTABLE LEGUME
EPICOTYL

Bouffil (13) divided the life span of the peanut into three stages: 1.
germination, 2. preflowering, 3. flowering, fruiting, and maturation. The
first of these covered the period of time necessary for emergence, i.e., in
Senegal, about 4 days. The period of preflowering extended from the end of
the first period to the appearance of the first flower, or about 26 days. The
third stage, flowering, fruiting, and maturation, began with the first flower
and lasted to maturity or about 80 to 90 days. This life span corresponds to
the earliest peanuts known to growers in the United States. Comparable
periods in some of the types grown in America would be 7 to 10 days, 30
days, and 120 days.

Figure 8.—Cotyledon from 11-day old peanut seedling, cross section. In contrast to
the condition at five days, much of the stored food-has disappeared and the
cell contents are lightly stained. Irregular dark patches result from the collapse
of the tissues in these areas. (after Yarbrough, 76.) '

MORPHOLOGY, GENETICS AND BREEDING 41

The basic morphological pattern of the epicotyl is laid down in the
seed. Its main axes consists of a central stem and two cotyledonary lat-
erals (figure 10). Contrary to the situation in many plants, at least after
the first 3 weeks, the main axis of the shoot exerts little inhibitory effect
on lateral axes. The main axis develops first but is soon equalled in
length by each of the two cotyledonary laterals, and eventually may be
much exceeded by them. From the beginning the plant is provided with
three active shoot apices. The third and fourth lateral axes arise from
the central stem subtended by its first two foliage leaves. These no doubt
are the four branches described by Bouffil (13) but two of them appear
much later than he indicates. In Virginia type peanuts additional vege-
tative branch axes commonly arise from the first two nodes of each

brough, 76.)

42 THE PEANUT—THE UNPREDICTABLE LEGUME

Figure 10.—Peanut seedling, eleven and one-half days old. The root system is well
developed. Four leaves of the main axis are visible and the two cotyledonary
lateral branches have begun to expand. All of the shoot organs visible here
have expanded from fully formed structures of the embryonic epicotyl shown in
figure 1. (after Yarbrough, 76.)

MORPHOLOGY, GENETICS AND BREEDING 43

cotyledonary lateral, subtended by reduced foliar scales known as
cataphylls. These are found as the first two foliar organs of all lateral
axes. The cataphyllar internodes are usually short and on the lower
branches are frequently covered with soil during cultivation.

In Virginia type peanuts the first reproductive branch generally ap-
pears in the axil of the first foliage leaf on one of the cotylédonary laterals.
No reproductive branches occur directly on the main stem in Virginia.
A reproductive branch may occur in the axil of the second cataphyll but
none has been reported or observed in the axil of the first cataphyll. The
first reproductive branches in Spanish and Valencia types occur at the
first cataphyllar nodes on the cotyledonary laterals. Later reproductive
branches also occur on the main stem.

VEGETATIVE STRUCTURE OF THE MATURE PLANT

A detailed anatomy of the mature peanut plant has not been written.
The general morphology, habit of growth, branching habit, and general
appearance of the plant have been described with varying degrees: of
thoroughness. Much of this description is to be found in the taxonomic
treatments of the genus and its relatives. Although we are not primarily
concerned here with the systematics of peanuts, we find the published
descriptive accounts of the species one of our best sources of general
morphological information.

Root

Hoehne (34) has described the genus as perennial. The root systems
of all the wild species develop much-branched, woody structures and all,
including our cultivated form, last more than one year. In A. hypogaea

the root system may penetrate to a depth of 3 to 4 feet in cultivated |

fields (Yarbrough 76). In some wild species the root systems become
tuberous and fleshy (figure 11). This characteristic is not confined to A.
tuberosa but is also found in A. marginata (34). When. grown in the
United States, wild species received from South America show variable
development of the tuberous habit, but even in forms generally not
thought to possess tubers this character is somewhat apparent. Of the
species seen by the authors, only in A. hypogaea do the roots appear to
be entirely non-tuberous. At present we do not know whether or not
this character would develop in specimens of A. hypogaea grown for sev-
eral years. Hoehne (34) considered the tubers to be food storage organs
which assist in carrying the plants over unfavorable periods of the year.

44 THE PEANUT—THE UNPREDICTABLE LEGUME

Figure 11—Tuberous root system of Arachis marginata. Tap-rooted as in A. hypo-
gaea, this root system differs from the cultivated species in the development of
fleshy thickening.

Figure 12.—Root system of Arachis hypogaea. This root system with its well-de-
veloped tap root may penetrate the soil to a depth of 3-4 feet. Note the abundance
of lateral roots with fibrous rootlets, but the absence of fleshy thickening,

MORPHOLOGY, GENETICS AND BREEDING 45

So far as is known these structures have not been put to practical use
by man.

The root system in A. hypogaea consists of a tap root with many
laterals (figures 10 and 12) and adventitious roots from the hypocotyl
and aerial branches. The nature of the much-branched and vari-formed
adventitious roots developing from the bacterial nodules (Prevot, 54)
has not been clarified.* Prevot suggested certain possible functions for
such roots but these have not been experimentally verified. Some of the
wild species frequently develop extensive branching roots from the pegs

(Gregory, 27). A. hypogaea has been observed to do this occasionally

but in such cases the roots can usually | be seen to develop from « callus
tissue following wot wounding of the peg or pod. The development of root

hairs has not been studied ar ie in A. hypogaea or at all in the
wild species.

STEMS'

The cultivated peanut is ordinarily (1) erect (bunch) or (2) pros-
trate (running) although intermediate growth forms occur. In both cases
there is an erect primary br anch which serves as the axis of the plant and
gives rise to various lateral branches. The central axis (main stem) de-
velops from the terminal bud of the epicotyl and is flanked by two oppo-
site, lateral branches which arise from the respective cotyledonary axils.
The central axis is always erect but may be relatively short in the pros-
trate varieties. In the erect varieties the lateral branches are also erect
or ascending, but even in these types the plants may become semi-
decumbent as growth proceeds. In contrast, the main lateral branches of
the truly prostrate varieties always grow peripherally from the main axis
and usually lie within an inch of the ground except at their tips, which
may be somewhat ascending.

Working with cuttings, Harvey and Schultz (29) observed in an
erect type that main stem and lateral cuttings produced plants which
were essentially similar in flowering habit to the control plants grown
from seed. In two other varieties, characterized by non-flowering main
stems, the main stem cuttings produced no flowers on the original axis
but produced laterals in a manner comparable to the seedlings. The cut-
tings of the laterals continued to behave as laterals, however, and pro-
duced inflorescences on all branches including the initial axis which
had been cut from the parent lateral. One of these varieties was distinctly

*In his figure 13, Prevot (54) illustrated a cluster of these roots on which the nodules pro-
duced a number of white rootlets, having the appearance of roots grown under the influence of
heteroauxin. These rootlets were thickened, short, and often had claviform ends. It may be
noted that these roots appear very similar to those infested with nematodes.

46 THE PEANUT—THE UNPREDICTABLE LEGUME

prostrate and the cuttings of its laterals not only flowered, but also con-
tinued to be prostrate, growing entirely in one direction from the original
point of root attachment. Clearly in this case, the polarity in development
which controlled the original lateral branch was maintained independently
in the excised portions.

The stems of A. hypogaea are angular at first, containing a solid
pith which breaks down eventually so that old stems are hollow. The
angularity is also lost with age, the older branches becoming cylindrical.
There is no indication of woody development in the aerial portions of
Arachis. The genus consists exclusively of herbaceous perennials; pos-
sibly some forms of A. hypogaea should be considered annual.

A variety of other growth forms are found among the wild species of
Arachis. Hoehne (34) described these briefly in his monograph but at-
tached little systematic importance to the variation present. The rhizo-
matous habit is clearly present in A. glabrata, for example, while several
of the species are stoloniferous, the stolons being partially buried at times.

The pattern, order, and kinds of branching in the peanut are one of
the most interesting botanical features of the plant. Richter (59) gave a
brief description of branching orders wherein he let the central stem axis
of the plant be an axis of the » order. Branches arising from the n order
axis were of 2+ 1 order and branches arising from n+1 order axes
were 2 + 2 order, etc. Branches arising in the axils of the foliage leaves
were of two kinds, (1) vegetative and (2) reproductive. Since repro-
ductive branches normally do not give rise to further branching, their
production terminated all further orders of branching. For example, in
Richter’s material, » + 3 order reproductive branches, by their specific
morphology, terminated the branching system. Prevot’s (54) diagram
in his figure 10 shows a branching pattern similar to the type described
by Richter (59). We have observed branching systems of several varie-
ties of A. hypogaea and found that these differed widely not only in the
numbers of branching orders produced but also because they fell into
certain well defined patterns.

LEAVES

Leaves of peanuts are usually pinnate with two pairs of leaflets.
Hoehne (34) reports that at least one species, and perhaps two are nor-
mally trifoliate. The leaflets may be elliptic-obovate, (A. hypogaea), ellip-
tic-lanceolate, (4. glabrata) or almost linear (A. angustifolia). The
leaflets may have inrolled margins or varying development of marginal
hairs. Hoehne (34) makes extensive use of these characters in his de-
scription of species. The leaves of the several species may be dark dull

MORPHOLOGY, GENETICS AND BREEDING 47

green, dark blue green, pea green or yellow green. In A. hypogaea this
variation is pronounced and has been shown to be genetic in origin. The
dark dull green of one tuberous-rooted wild species (A. marginata) has
not been seen in A. hypogaea but is approached in certain Chinese forms. °
The genetic segregation for depth of chlorophyll green in A. hypogaea
leads to the general supposition that the variations in leaf color between
wild species are also genetic in nature and are not primarily a matter of
mineral nutrition as might be suggested by cultivated fields of A. hypo-
gaea differing in available nitrogen, calcium, and other mineral elements.

The arrangement of the leaves on A. hypogaea is intimately associ-
ated with the branching habit of the plant. The leaves occur alternately,
one at each node, and describe a 2/5 phyllotaxy (Richter, 59). Embry-
onic leaves on the main stem axis are well formed and ordinarily saow
little or no reduction in size. This is far from the case on all primary
and secondary laterals. As one proceeds towards the base from the tips
of such branches, the leaves usually show reduction in size and at the
lowermost nodes also show a reduction in number of parts and complete-
ness of form until at the first and usually the second node, the leaves are
represented by mere scales known as cataphylls. Branches arising in the
axils of the foliage leaves may be either vegetative or reproductive. In
either case the first two nodes are cataphyllar.

The morphology of the mature foliage leaf of cultivated peanuts has
been described rather completely. The leaf is even-pinnate with four
obovate to elliptical leaflets. Two large, long-lanceolate stipules enclose
the leaf in the bud. Stomata occur on both surfaces of the leaves. Varia-
tions in organization of leaves of seedlings and older plants include oc-
casional quinque-foliate, trifoliolate, bifoliolate, and even unifoliolate
types.

Reed (55) illustrated sections of the leaflets and emphasized the
presence of water storage cells_in_ the spongy mesophyll. This water
storage tissue, associated with typical mesophytic leaf structure, led him
to speculate concerning the intermediate ecological position of the peanut
between _xerophyte and mesophyte. These speculations may prove to be
well founded, for peanuts are capable of withstanding long periods of
dry weather but give a typical mesophytic response to relief by rains.
The peanut’s ability to withstand adverse water conditions, its adaptation
to soils of deep sand, and its geocarpic habit conform to what we know
of the habits, geographic distribution, and ecology of other geocarpic
and amphicarpic species. Whether the water storage cells of the leaflets
play a functional role in this complex of factors is unknown.

48 THE PEANUT—THE UNPREDICTABLE LEGUME
REPRODUCTIVE MORPHOLOGY
INFLORESCENCE

Kurtz (41) described the inflorescences of the peanut as two to
three-flowered, occurring in the leaf axils, but Pettit (50) merely stated

Figure 13.—-A well-developed peanut inflorescence; b, bract (cataphyll) subtending
a floral branch; f, bract (cataphyll) subtending a flower; p. peg; t, terminal
bud of the inflorescence. An axillary floral branch arises at each node of the
zig-zag inflorescence axis. The cataphylls have the same relation to the axillary
branches of this subpaniculate inflorescence as leaves have to the lateral
branches of a vegetative shoot.

MORPHOLOGY, GENETICS AND BREEDING 49

that the flowers develop in the axils of the leaves. Richter (59) described
the inflorescence with its bracts as an axillary head or compressed spike
with a 2/5 phyllotaxy in the arrangement of its flowers.

In systematic treatments of Arachis, the inflorescence is described as
spicate or subpaniculate. The inflorescences are not terminal but always
occur in the axils of foliage leaves or cataphylls. They never occur at the
same nodes with vegetative branches and form with the latter a definite
branching pattern. Each inflorescence bears three to several flowers. The
flowers usually appear one at a time but two may open simultaneously
in the Spanish type. Flowers on the same inflorescence may appear daily
or at intervals of several days.

An inflorescence (figure 13) irrespective of whether it arises in the
axil of a foliage leaf or in the axil of a cataphyll, produces a cataphyll
at its first node. Each successive node of the inflorescence also has its
cataphylf in the axil of which arises the simple flowering branch. The
flowering branch is exceedingly short and possesses a single cataphyll,
bifid or simple, in the axil of which the flower bud appears to develop.
The production of the flower terminates further branching. The in-
florescence can be seen then as a reduced and compressed replica of the
vegetative shoot reduplicating its phyllotaxy and axillary buds, differ-
ing largely from the latter in the reduction of organs and the suppression
of further growth through the production of flowers. The internodes of
the central axis of the inflorescence may later elongate, producing a
much expanded fruiting structure. The growing point of the central axis
occasionally becomes vegetative and pursues a limited amount of
growth. New inflorescences may then be laid down in the axils of the
foliage leaves occurring at the end of the oroginal inflorescence. Thus it
can be seen that what is customarily a reduced and simplified branching
system sometimes may become so involved that at maturity the untrained
observer cannot distinguish vegetative from reproductive branches.

FLOWER

The flowers (figure 14) of Arachis are yellow, papilionate, and sessile.
The dev lpr ofa remarkable perigyny involving an unusually Jong.

serted practically at the ond of the simple flowering branch and is sub-
tended directly by its cataphyllar bract. The hypanthium is pubescent.
The external portion of the tube expands above into five calyx teeth,
four of which are fused into a superior lip which stands back of the

50 THE PEANUT—THE UNPREDICTABLE LEGUME

standard. The fifth tooth is linear and lies under the keel. The petals and
staminal column are adnate at their bases and are inserted together at the
summit of the tube. The standard is broadly inserted while the wings
and keel are attached by means of claws. The staminal column is usually

\ Se

Figure 14.—A peanut flower as seen in longitudinal optical section. S, standard; W,
wing; St, stigma; A, anthers; C. calyx lobe; K, keel; T, staminal column;
Style; “C tube”, hypanthium (“calyx tube”); O, ovary; Sc, bracts (b and f
of fig. 13). At lower right the ovary (O) is shown in enlarged section; Ov,
ovule; Es. embryo sac. (after Smith, 66.)

MORPHOLOGY, GENETICS AND BREEDING 51

composed of ten filaments, eight of which are normally anther bearing.
The filaments are fused through one-half to two-thirds of their lengths.
The stamens occur in two series, four bearing oblong, adnate, introrse
anthers which alternate with four filaments bearing globose, dorsifixed
anthers. Three of the oblong anthers are biloculate; the fourth, adjacent
to the sterile filaments, is usually uniloculate. The four globose anthers
are uniloculate. In bud stages the filaments bearing the oblong anthers
exceed the others. The staminal column lies horizontally to the hypan-
thium. At the point of separation the free ends of the filaments are sharply
reflexed toward the standard, forming acute angles with their fused
bases. The pistil consists of a single, sessile carpel (Smith, 66),1.5 mm.
long and 0.5 mm. in basal diameter, surmounted obliquely by the long
filiform style which extends through the hypanthium, bends sharply
through the staminal column, bends sharply again with the reflexed fila-
ments, and ends in a club-shaped stigma above the anthers. Near its sum-
mit on the surface facing the standard, the style is clothed with upward
slanting hairs.

Twenty-four hours before anthesis the flower bud is 6 to 10 mm.
long (Smith, 66). During the day elongation of the bud proceeds slowly
but when night falls elongation accelerates. At the time of anthesis, near
sunrise the following day, the flowers may be from 50-70 mm. long. The
oblong anthers dehisce just before, sometimes after petal expansion. The
globose anthers dehisce subsequent to further elongation of their fila-
ments, which eventually equal or exceed those of the oblong group
(Badami, 3; Smith, 66).

Peanut flowers which are fresh and turgid at sunrise are usually
wilted by midday, although they last longer in cool weather. On the day
after flowering all the flower parts except the small, sessile ovary have
withered, as Didrichsen (22) clearly demonstrated in 1866. The hy-
panthium soon abscisses leaving a circular scar at the base of the ovary.
The old flower parts sometimes adhere to the tip of the ovary during early
peg growth.

wo ’
ee
The peg is the most distinctive feature of the peanut plant, for it is
by means of this structure that the aerial flowers come to mature their
fruits underground ( figure 15). The peg has been variously described as
an apetalous flower or more recently as a gynophore, a stalk upon which
the the ovary rests rests. The various interpretations and terms applied ‘to this
‘structure have been reviewed by Smith (66). He has defined the peg as

52 THE PEANUT—THE UNPREDICTABLE LEGUME

“the young fruit during the stalk-like phases of development which inter-
vene between syngamy and fruit enlargement.” Smith has shown that this
stalk-like organ is not a gynophore but in reality the ovary, elongated by
the growth of an intercalary meristem in its base. Jacobs (39) has de-
scribed the development of this meristem and the differentiation of the
tissues arising from it. He has shown that the vascular ar strands extend
through the meristematic region to the base of the ovarian cavity. The
loculus of the ovary, distal to meristem in the tip of the peg, contains
the 2 to 6 ovules.

The ovary is enclosed by cataphylls of the inflorescence, which in
turn are covered by the stipules of the subtending leaf. Peg growth be-
gins immediately after fertilization and the peg usually appears from
within the enclosing bracts and stipules several days after anthesis. Early
growth is slow but gradually accelerates until the pegs are elongating very
rapidly.

The peg is positively geotropic. Charles Darwin (21) showed in
1880 that the peg was not negatively phototropic but did respond to the
force of gravity. The later observations of Badami (3), Jacobs (39),
Shibuya (65), Theune (71) and Waldron (75) have supported this
view. The ultimate length of a peg and the time required for it to reach
the soil is determined by the initial distance from the ground. Pegs in-
serted more than 15 cm. above the soil surface usually fail to reach the
ground. In such circumstances, the peg tips usually fail to reach the
ground. In such circumstances, the peg tips usually die and pod and seed
development do not occur. Exceptionally, ovule enlargement does occur
and viable seed develop in aerial pegs, but normal pods are not formed
(Gregory in Smith, 66).

Upon penetrating the soil the peg commonly grows to a depth of 2
to 7 cm. (but may be covered much deeper than this by cultivation). For
several centimeters immediately above the soil surface the peg sometimes
becomes fleshy and much thickened, and loses its green or purple color.
Its lenticels become enlarged and irregular. Many multicellular hairs may
be found on the peg surface. Underground the peg may become similarly
expanded and have copious hairs. The function of these hairs is proble-
matical. Pettit (50) and Waldron (75) have interpreted the hairs of the
peg and pod as “root hairs” in structure and function, but Richter (59)
found their cell walls suberized. He suggested that they anchored the
peg in the soil. These hairs are not root hairs but are multicellular
trichomes characteristic of stems. “ae

MORPHOLOGY, GENETICS AND BREEDING 53

Pop
When the peg reaches its maximum penetration of the soil it loses its
geotropism and the tip turns to a horizontal position. At the same time
the pod begins to enlarge and development rapidly ensues. Enlargement
of the pod proceeds from base to apex (figure 15). Early stages resemble

Sou |

Ineh

Figure 15.—Successive stages in the development of a peanut fruit. Left to right: an
ovary at time of fertilization; young aerial peg; elongated peg after soil pene-
tration; the tip of the peg turned to a horizontai position and the beginning of
pod enlargement; early immature stage of pod development; mature fruit.
(after Smith, 66.)

one-seeded pods in appearance. The more rapid development of the basal

segment is associated with the earlier development of the basal seed.

When the apical seed aborts, as occurs frequently, enlargement of the

apical portion proceeds no further.

At maturity, the shell is usually reticulate and more or less constricted
between the seeds. According to Thompson (72) and Russell (63) the
superficial exocarp layers flake off during development. The character-
istic reticulations underlying the veins are ridges of mechanical tissue
arising as outward extensions of the sclerenchymatous mesocarp layer.
This layer is continuous except at the sutures. The endocarp consists of
a parenchymatous tissue which surrounds the ovules during development.
The cells of the endocarp lose their contents and their walls collapse as
the pod matures.

The peanut fruit is a one-loculed, structurally dehiscent, but func-

54 THE PEANUT—THE UNPREDICTABLE LEGUME

tionally indehiscent legume. Under pressure the pod tends to split along
a longitudinal ventral suture. Examining cross sections, Richter (59) ob-
served that the mechanical tissue of the mesocarp was interrupted along
this line. He demonstrated that this was the line of normal dehiscence by
cutting the pod into rings and then passing the rings over suitably sized
chick peas. The peas were allowed to swell; the rings were always broken
along the suture.

The thickness of the pericarp or shell and the ease with which it may
be broken open, differ greatly in the different varieties of A. hypogaea.
The shell may be paper thin or more than 2 mm. thick. There appears
to be a positive correlation between size of fruit and thickness of shell but
in segregating progenies of thick-large x thin-small peanuts, thick-small
and thin-large types occasionally appear. In no case, however, have the
writers observed thinnest-largest or thickest-smallest combinations.

The peanut pod varies in size from about 1 x 0.5 to 8 x 2 cm. and
may contain from 1 to 6 seeds. The seeds are suspended from the inner,
ventral (upper) surface of the pericarp. The attachment and hence the
hilum always lies toward the apex of the seed-bearing segment. A limited
elongation may take place in the isthmus between two seed-bearing seg-
ments of the pod in some varieties of A. hypogaea.

EMBRYO AND SEED

The internal processes leading to the formation of the embryo sac and
the embryo were first treated by Reed (55) and with somewhat greater
accuracy by Banerji (4). Embryo sac development and early embryo and
endosperm growth have been more recently and fully treated by Smith
(68). The frequent occurrence of seed failure, commonly observed as
“pops” and one-seeded pods in cultivated peanuts, led Smith to investi-
gate the basic reproductive processes which occur in the ovule just before
and after flowering.

In the peanut, a single megaspore mother cell in each ovule under-
goes a normal meiosis and produces four megaspores. The lowest
(chalazal) spore develops into the 7-celled, 8-nucleate embryo sac, while
the other spores degenerate. This embryo sac corresponds to the “nor-
mal type’ found in other legumes and found in the majority of the in-
vestigated cases in flowering plants. By the time of pollination, the
synergids and antipodal cells have usually degenerated so that the sac con-
sists of only the egg cell and a large central cell containing the two polar
nuclei.

The union of egg and sperm occurs 12 to 16 hours after pollination.

MORPHOLOGY, GENETICS AND BREEDING 55

At the same time, the polar nuclei fuses with the second sperm nucleus.
The primary endosperm nucleus resulting from this triple fusion divides
first, usually within 8 to 12 hours after fertilization. The zygote has
usually divided to form a two-celled embryo within 36 hours.

During the first 10 to 12 days after flowering, growth proceeds slowly
in both embryo and endosperm, but in this same period the peg, after a
slow start, grows rapidly and usually approaches or reaches the soil
surface. From the fifth to the tenth day of fruit development, the growth
and elongation of the peg accelerate rapidly. During this same period
cell and nuclear divisions are virtually absent in the embryo and endo-
sperm (Smith, 68). After the tenth day, both embryo and endosperm
begin to grow rapidly in normally developing seeds, concurrently with
the beginning of underground pod enlargement. The durations of the
early stages of both peg and seed development vary widely as a result
of position on the plant, competition with other fruits, and other environ-
mental circumstances.

More than 93 percent of the eggs have been reported as fertilized
and about 12 percent of the early embryos as aborting during the first
two weeks of growth (Smith, 67). As most of the fertilization failures
or embryo abortions occurred singly in the apical ovules, approximately
14 percent of the pegs studied contained a single developing seed in the
basal position. This value is compared with 18 percent one-segmented,
one-seeded pods which were harvested in the control sample. Failure of
fertilization and early embryo abortion appear to account for the occur-
rence of most of the one-seeded fruits so frequently seen.

It is equally evident from these results that normal megasporogenesis,
embryo sac development, and fertilization provide no basis for predicting
the occurrence of the later seed failures which give rise to the shriveled
seeds and empty pods characteristic of the pop condition. When a young
seed fails during the peg stage, the portion of the ovary containing it also
fails to grow. Failures of the seed after underground pod enlargement has
begun do not seem to inhibit the completion of pod development. Thus,
recent data (68) are in harmony with the conclusions of Burkhart and
Collins (15) and of Colwell and Brady (18) that calcium deficiency in
the fruiting zone of the soil is a principal cause of the “pop” condition.

FLOWERING AND FRUITING

Peanut flowers begin to appear 4 to 6 weeks after planting. Richter
(59) observed that in contrast to flowers of most plants, those of peanuts
are most abundant on the lower nodes. He considered this an adaptation

56 THE PEANUT—THE UNPREDICTABLE LEGUME

to the geocarpic habit of the plant. He noted that the pegs and mature
fruits are also concentrated at the lower nodes. In more suitable climates
than that of Breslau where Richter worked, flowering and peg formation
occur much farther up the stem than he suspected, flowers appearing
even at the last visible node. He was essentially correct, however, in say-
ing that peg production is suppressed at the upper nodes.

The daily production of flowers during the life of the peanut plant
has been described by Shibuya (65), Bouffil (13), and Smith (66).
Bouffil illustrated frequencies of flower production by days for five con-
secutive seasons. He compared his frequency distributions with the distri-
bution given by Shibuya for Formosa as well as with a distribution from
material grown in the neighborhood of Paris. All of his graphs and those
from Shibuya’s data are similar. Smith found also that flower-frequency
curves obtained during three seasons from North Carolina material
closely resembled those of Bouffil. Careful records of hours of sunlight
and amounts of rainfall were available to Bouffil, temperature being vir-
tually constant in Senegal, and he stated that the pattern of flowering was
not influenced by meteorological conditions. In the data from the Paris
area the number of flowers was much reduced but the general pattern was
not altered.

Bouffil’s analysis of flowering frequency led him to describe four
stages in the progression of flowering: (1) slow increase, (2) fast in-
crease, (3) flowering peak, and (4) decline of flowering. Smith described
the onset of flowering as gradual with flower production beginning to
accelerate after two to three weeks. Peak production was reached four to
six weeks after the first flowers appeared, the time depending upon variety ;
then flowering decreased at approximately the same rates as the increases
occurred. In a Spanish strain, two-thirds of the flowers were produced
during a one month period beginning six weeks after planting; in a Vir-
ginia runner, four-fifths of the flowers were produced during the third
month after planting (figure 16).

The following fertility coefficients for Bouffil’s line 24-11 are based
on means of 90, 89, and 64 plants, respectively, grown at the M’Bambey
Station, Senegal.

Mean flowers Mean pods Fertility coeffi-
per plant per plant cient, flowers /pod
QAO ssc tenis cesarean ened 599 133 4.5 (flowers)
LOB oti soled somlacreteninei ol weeders 751.3 161.3 4.65 mn
1942: oncom eur ag eane tae 578 68.8 8.4 “

MORPHOLOGY, GENETICS AND BREEDING 57

oat
a
5
= oisb
a
2
wo
=
a io L
4
o
=
D>
Z si
2
a
=
VIRGINIA JUMBO RUNNER
30.~7 4. tSC« " ie. 25 8
JUNE JULY AUGUST SEPTEMBER
DAILY FLOWER PRODUCTION IN ARACHIS
1944 SEASON
RALEIGH, N.C.

Figure 16.—The seasonal distribution of flower production in a Virginia peanut.
(after Smith, 67.)

Gregory’s data (26) from artificially pollinated flowers, all flowers
not used being removed from the plants, showed a fertility coefficient of
nearly 2, twice as efficient as Bouffil’s 1940 and 1941 values and 4 times
as efficient as his 1942 figure. Smith (67) reported that 63 percent of
the flowers studied produced pegs and one-third of the pegs developed
pods, but only 13.5 percent of the original flowers produced mature
fruits (figure 17). Expressed as flowers per fruit the fertility coefficient
was 7.9.

AERIAL FLOWER—SUBTERRANEAN FRUIT

From the time that the peanut first became known to Europeans, its
flowering and fruiting habits attracted widespread attention. In spite of
perennial interest in this botanical curiosity, many misconceptions have
arisen concerning the structure of its flowers and their relation to nor-
mal fruiting. Even today one can hear the statement that the yellow
flowers of peanuts have nothing to do with the production of fruit and
that there exist peanuts capable of producing 2000 pounds of nuts per

58 THE PEANUT—THE UNPREDICTABLE LEGUME

acre without bearing a single yellow flower. Smith (66) has recently
written a review of the controversy which arose among botanists over
the manner in which peanuts produce their fruits, and the resulting mis-
conceptions which still persist.

The first accurate description of the peanut flower was published by
Poiteau in 1806 (52). Nevertheless, in 1839, Bentham (10) stated that
peanuts possessed two kinds of flowers, one of the showy, yellow, flower

PER CENT
Es Selva eth een Bay eiot ay SSS Sym ie, 100.0 OVULES PRODUCED

(9 cin eRe SeEwee ase eREeeh Ss 93.3 EGGS FERTILIZED

Sel eicransistc Sereibis ecleraerets 63.5 OVULES IN PEGS AND PODS

Wns sites e ss pee 21.4 OVULES IN ALL PODS

weees Heelies 13.5 OVULES IN MATURE PODS

">. 11.2 SEEDS, SOIL GALCIUM ADEQUATE
“7.1 SEEDS, SOIL CALCIUM DEFICIENT

REPRODUCTIVE EFFICIENCY IN ARACHIS HYPOGAEA

10 VIRGINIA JUMBO RUNNER PLANTS
5233 FLOWERS, 2 OVULES PER FLOWER

Figure 17. The production of flowers, pegs, pods, and seed in a Virginia peanut.
(after Smith, 67.)

considered to be sterile; the other, with neither calyx, corolla, nor sta-
mens, which produced the fruit. In other words, he not only did not see
the relationship between the flowers and the fruits, but he also thought
that the pegs were some kind of peculiar flower. Later Bentham was in-
volved in a controversy with a gentleman from Georgia named Neisler
(46) who correctly described the relationship of flowers, pegs, and ma-
ture fruits in 1855. Meanwhile, in 1853, Poiteau (53) had restated his
position of 1806. Although Bentham recognized his own error in 1856
(see Gray, 25) and corrected it (11), Didrichsen (22) in 1866, and

MORPHOLOGY, GENETICS AND BREEDING 59

Kurtz (41) in 1875, failed to discover Bentham’s retraction and criti-
cized him severely. Other writers have overlooked Bentham’s (11) cor-
rection of his mistake, and one may find his erroneous concept in many
recent reference works and texts which Smith (66) has cited. The read-
ers of these usually reliable works of the past 40 years will do well to be-
ware while perusing the section dealing with Arachis hypogaea.

VARIABILITY, GENETICS AND BREEDING

VARIABILITY

In the preceding pages of this chapter we have described in general
terms the form, structure, and reproductive morphology of peanuts. On
occasion we have given ranges of size, number, and kinds of some of the
things described. It should be borne in mind, however, that the detailed
studies necessary to the descriptive morphology of a plant cannot pos-
sibly characterize all the plants in a genus, a species, or even a single va-
riety. It is the common possession of certain basic features, however,
which leads to the establishment of such taxonomic entities. The confi-
dence with which we place a group of plants in a single taxonomic cate-
gory is based on no more than a conceived average of the almost universal
variability found in any natural group. It is the discovery that this range
of variation extends beyond the accepted but sometimes ill-defined limits
which leads to the creation of new varieties, species, genera, or higher
taxonomic categories.

The systematic position of the genus Arachis was for a long time a
moot question. In 1839 Bentham (10) first properly associated Arachis
with Stylosanthes and Chapmannia in the tribe Hedysareae. Taubert (70)
separated the tribe Hedysareae (which includes such plants as beggar’s
ticks and lespedeza) into six subtribes; the last of these, the Stylos-
anthineae, includes the peanut and its relatives. This subtribe includes
only four genera, Zornia, Chapmannia, Stylosanthes, and Arachis. They
possess in common the following features :

“Stamens all united into a closed tube; anthers alternately basally*
and dorsally attached; flowers in terminal or axillary spikes or small
heads, seldom somewhat raceme-like; leaves pinnate, mostly with few
leaflets, without stipels.” (Taubert, 70. Translated from the German).
Arachis, Stylosanthes, and Chapmannia form a closely related group, all
of them possessing the characteristic tubular hypanthium, pinnate leaves,
and straight embryo. Zornia differs materially from the rest of the tribe

* Adnate, introrse in Arachis—author’s note.

60 THE PEANUT—THE UNPREDICTABLE LEGUME

in not possessing any of these distinctive features. As described by Burk-
art (14), Hoehne (34), and Taubert (70) Arachis differs chiefly from
Stylosanthes and Chapmannia in producing pegs, being geocarpic, and in
producing most of its flowers on the lower nodes of the stem, while
Stylosanthes and Chapmannia have shorter hypanthia, produce no pegs,
have aerial fruits, and produce most of their flowers in the upper axils.

The genus Arachis itself, before 1839, consisted of only one species,
the cultivated peanut, A. hypogaea. Bentham, however, described five ad-
ditional species all collected from the wild in South America. Since that
time several additional species have been described.

Hoehne (34,35) recognized twelve species in the genus Arachis.
These, with their subspecies and forms, are listed below:

A. tuberosa Benth. A. prostrata Benth.
A. guaranitica Chod. & Hassl. Subspecies: Hagenbeckii (Harms)
A. Diogoi Hoehne Hoehne
Form: typica Hoehne A. marginata Gardn.
Form: subglabrata Hoehne Form: submarginata Hoehne
Form: sericeo-villosa Hoehne A, nambyquarae Hoehne
Form: submarginata Hoehne A. hypogaea L.
Form :minor Hoehne Forms: various
Subspecies : major Hoehne A, glabrata Benth.
A. angustifolia (Chod. & Hassl.) Killip Form: typica Hoehne
A. helodes Mart. Form: major Hoehne
A. villosa Benth. Form: minor Hoehne

A. villosulicarpa Hoehne

VARIETIES OF ARACHIS HYPOGAEA L.

The different forms of 4. hypogaea have stimulated various workers
to develop varietal classifications of the cultivated peanut. Taxonomists
frequently resort to controversy concerning species delineation because
the ultimate nature of organic variation necessarily leads to intergrading
forms. If the species problem is difficult, the varietal problem becomes
nearly impossible. Yet as certain species grade into one another, varietal
clusters tend to assume sufficient distinctness to approximate specific
rank. Depending on the chance evolutionary time level at which any ob-
server may happen to approach such clusters, he will find himself con-
fronted with a continuous array of variability at one extreme or almost
species-distinct varietal clusters at the other. Cultivated peanut varieties
appear to fall somewhere between these two extremes, different enough
to be interesting yet similar enough to be exasperating.

In his study of the origin of cultivated peanuts, Dubard (23) suggested
that the forms which were transported from Brazil to the west coast of

MORPHOLOGY, GENETICS AND BREEDING 61

Africa were varietally distinct and more primitive than those peanuts of
Peru which had found their way into Mexico in pre-Columbian times,
and later travelled from Peru to the islands of the Pacific, East Asia, and
as far as Madagascar. The latter forms reached Spain via France from
Mexico. The varietal terms ‘‘African’’ and “Asian” arose from this post-
Columbian distribution of cultivated peanut forms. There can be little
question but that the peanut known in the United States as “Valencia” is
the Peruvian-Mexican-Asian-Spanish (Archbishop of Valence) form.

Chevalier (16) noted that the upright and prostrate habits of peanuts
were insufficient grounds for establishing subspecies.

Some 40 varieties were listed by Hayes (30) who gave their countries
of origin. His classification divided A. hypogaea into runner and bunch
varieties. Four groups of varieties were separated under his bunch group
on the basis of such characters as corolla color, seed-coat color, hairiness,
etc. Six runner groups were similarly separated on the basis of such
superficial characters.

John and Seshadri (40) went so far as to give a Latin description of
a variety “gigantea” which they had discovered among the segregating
progeny following a cross.

Hull (36) stated that the peanuts which he used in a genetic study
fell into three groups, runner, Spanish and Valencia. °

Clos (17) used the following ten characteristics in classifying the
types of peanuts grown in Argentina: Carriage of the plants, color of
the seed coats, number of seeds per fruit, size of fruits, constriction of the
fruits, elevation of fruit venation, color of the stalk, pubescence of the
stalk, weight of the seeds, and venation of the seeds. Like Hayes, Clos
divided cultivated peanuts into two main groups, upright and prostrate.
Then by means of the characters listed above he isolated eleven upright
types and four prostrate types known in Argentina.

More recently Bouffil (13) has stated that the only characters which
are of any value in varietal classification are (1) the carriage of the
plant, and (2) the presence or absence of a rest period in the seeds. He
further states that characters ordinarily utilized in the classification of
plants are of no value in separating varieties of peanuts. He disagrees
with Chevalier (16) and separates A. hypogaea into two subspecies on
the basis of whether the plans are prostrate or upright. His classification
follows:

A. Plants prostrate
A. hypogaea subsp. africana
(a) Early maturity, immediate germination: var. praecor
(b) Late maturity, delayed germination: var. tarda

62 THE PEANUT—THE UNPREDICTABLE LEGUME

AA. Plants erect
A, hypogaea subsp. asiatica
(a) var. praecox
(b) var. tarda

When a large collection of types of peanuts are brought together, or
segregating progenies of varietal crosses are observed, one of their out-
standing features is the fact that any ordinarily accepted agronomic va-
riety has its own cluster of seed sizes; seed-coat colors; shell thicknesses,
reticulations, and constrictions; plant types; leaf colors, textures,
margins; and many other characters.

Before Europeans brought the varieties together and began artificial
crossing, self-pollination and geographic isolation led, in pre-Columbian
times, to the formation of rather distinct varietal groups. The authors
mentioned above, with the exception of Hull, have not produced a satis-
factory classification nor have they agreed with one another. Everyone
who has worked with peanuts can recognize the three varieties known
in the United States as Virginia, Spanish, and Valencia. If the agricul-
turist can identify these peanut varieties at a glance, there must be some
obvious morphological features which distinguish them.

Richter (59) correctly understood the morphology of the peanut in-
florescence and properly described it, but French, English, and American
workers have rarely referred to his excellent work. Richter specified in
clear morphological terms just where the inflorescences are produced, but
he did not provide illustrations. Cultivated peanuts apparently never pro-
duce flowers on the main axes of the plant, but on some more or less
well-developed axillary reproductive branch. The flowers, contrary to
scientific and popular opinion, never arise from the axils of foliage leaves.
It is the reproductive branch or inflorescence which thus arises. The in-
florescences produce scale leaves similar to cataphylls and it is in the
axils of these that the subsequent branches of the inflorescences bearing
the flowers are produced. Cataphylls (unless one calls cotyledons cata-
phylls) do not occur on the main stem axis.

Virginia peanuts differ from Spanish and Valencia peanuts in seldom,
if ever, producing an inflorescence from the first cataphyll of a lateral
branch of any order. This character is common to all forms of Virginia
peanuts. They may have large, medium, or small seed, and thick, inter-
mediate, or thin shells. They may be prostrate or upright but in the
basic features which lead a farmer to say, “Virginia Runner,” “Virginia
Bunch” or “some kind of a Virginia,” they are similar and may be dis-
tinguished from other peanuts. On the other hand, Spanish and Valencia
peanuts always produce inflorescences in the first cataphylls of secondary

MORPHOLOGY, GENETICS AND BREEDING 63

and higher order branches. This fact, in addition to the extreme reduction
of the first internode of most of the lateral branches, so that in second-
order branches the first cataphyll may be closely appressed to the main
stem, leads to the erroneous impression that twin buds occur in the leaf
axils on the main stem axis.

A botanical key to the varietal groups of peanuts follows:

A. Lateral buds of the central axis all vegetative. First cataphyllar node of
n-+1 order branches vegetative; second occasionally reproductive.*

(a) n4 2 order branches occur as pairs of vegetative branches alternating

with pairs of reproductive branches. Virginia

AA. Lateral buds of the central axis vegetative or reproductive. First and second

cataphyllar nodes of n+ 1 order branches reproductive. :

(a) n+2 order branches irregularly reproductive and vegetative. Pods

two to three seeded. Spanish

(aa) n+ 2 order branches all reproductive or sometimes mostly vegeta-

tive distal to the 6th-8th node. n + 3 order branches all reproductive.

Pods 3-6 seeded. Valencia

*See previous sections, Vegetative Structure of the Mature Plant: Stem; and Reproductive
Morphology: inflorescence. ‘

} . ‘
‘

Figure 18—An 2+ 1 order, cotyledonary lateral branch of a Virginia runner pea-
nut. Two n+ 2 vegetative branches arise from the first two nodes of this
branch, two n+ 2 reproductive branches from the next two nodes, two n + 2
vegetative branches from the next, two + 2 reproductive from the next...
The same pattern of alternating pairs of nodes appears on each successive order
(n+2,n+3, n+ 4) of vegetative branches, so that the occurrence of repro-
ductive branches does not limit the extent of the branching system. The branch-
ing order may but usually does not exceed x -+ 4 vegetative and +5 repro-
ductive in Virginia runners.

64 THE PEANUT—THE UNPREDICTABLE LEGUME

1. Virginia (figures 18, 19, 20).—Plants copiously branched, con-
sisting as in Valencia and Spanish of four or more principal lateral
branches. Laterals frequently far exceeding the main stem in length,
though of approximately the same length in some erect types. Main stem
nodes all vegetative. All lateral branches vegetative in the first node and
mostly vegetative in the second node. Nodes of the lateral branches of all
orders generally occur in alternating pairs of two vegetative and two re-
productive. Upper internodes 20-25 mm. in length. The main stem usually
produces many lateral branches in erect types or few in prostrate types.
Leaves and leaflet smaller, leaflets more firm and pointed elliptic than in
‘the two following; dark, glaucous green. Stems moderate in size less
coarse than in following, erect or prostrate. Fruits from 2-5 cm. in length
1-3 seeded, mostly 2 seeded. Shells thick or thin, reticulation usually
prominent. Constrictions between seeds apparent to marked. Seeds 0.5
gm.-2.0 gms., elongated and pointed, usually germinating only after 30-

Figure 19.—An +1 order, cotyledonary lateral branch of a Virginia bunch pea-
nut. The same succession of two »-+ 2 vegetative branches and two x+ 2 re-
productive branches occurs as is found in Virginia runner. The branching pat-
tern of the higher order (n + 2, n+ 3) vegetatives also consists of alternating
pairs of vegetative and reproductive branches. As in Virginia runner, the extent
of the branching order is indeterminate, but in Virginia bunch it usually does
not exceed n+ 3 V‘andn+4R.

MORPHOLOGY, GENETICS AND BREEDING 65

360 days “rest” period, usually pink, sometimes tan, rose, wine, red or
variegated red and white. Moderately resistant to cercospora leaf spot.

2. Spanish (figures 21, 22).—Plants moderately branched, consisting
of four or more main lateral branches arising as in Valencia. Main stem
and laterals usually of approximately equal lengths. Nodes of the main
stem above the principal laterals vegetative and reproductive; nodes of
laterals irregularly vegetative and reproductive, usually continuously re-
productive for as many as six nodes; frequently, however, vegetative at
nodes 3 and 4 on the cotyledonary laterals. First two nodes of lateral
branches reproductive. Inflorescences unbranched. Leaves and leaflets
similar to Valencia though usually somewhat smaller and paler green.
Upper internodes 20-30 mm. in length. Stems moderate in size, usually

Figure 20.—A Virginia bunch peanut in profile,

66 THE PEANUT—THE UNPREDICTABLE LEGUME

Figure 21—An +1 order, cotyledonary lateral branch of a Spanish peanut. The
+2 vegetative. branches occur sporadically and the »+2 reproductive
branches arise at the remaining nodes. The upper nodes are all reproductive as
are all the nodes of the »+2 vegetative branches. This is in contrast to the
regularly paired situation present in the Virginia variety. As in Valencia, the
branching een is determinate, ending with the production of #-++ 2 V which
producen+3R °

MORPHOLOGY, GENETICS AND BREEDING 67

smaller than in Valencia, mostly erect, green. Fruits variable in size, 1-3
cm., usually about 2 cm.; 1-3 seeded, mostly 2 seeded, clustered near the
base of the main stem. Shells thin, prominently veined ; beak small or
lacking. Constriction moderate to pronounced. Seeds variable, spherical
to rounded elliptic, sometimes red or pink, usually flesh, sometimes white,
0.2 gm.-0.5 gm., germinating immediately upon maturity. Highly sus-
ceptible to cercospora leaf spot.

3. Valencia (figures 23, 24).—Plants sparsely branched, consisting
usually of four (sometimes six) main lateral branches, one from each
cotyledonary axil and one from each of the first two foliage leaf axils of
the main stem. Main stem and laterals usually of approximately equal
lengths. Nodes of the main axis above the principal laterals mostly re-

Figure 22,—A Spanish peanut in profile.

68 THE PEANUT—THE UNPREDICTABLE LEGUME

productive. Nodes of the n + 1 laterals often continuously reproductive
for eight or more nodes. Vegetative branches occasional, rarely more
frequent on the n + 1 laterals and main stem axis. Highest order of vege-
tative branching, n + 2, frequently only n + 1. First two nodes of lateral
branches reproductive. Inflorescence sometimes branched. Leaves and
leaflets large. Upper internodes 30-35 mm. in length. Stems large, laterals
sometimes 7.5 mm. in diameter, coarse, mostly erect, occasionally lax;
frequently purple, but sometimes green. Fruits variable in size 2-6 cm.
long; 1-6 seeded, mostly 3-4 seeded. Shells variable, usually moderately
thick with only slightly raised venation ; sometimes thin with prominent
venation and beaked ; constrictions between the seeds slight, occasionally
more evident. Seeds variable, spherical or elongated, usually red or
purple-black, sometimes pink or flesh; 0.2 gm.-0.8 gm., usually about
0.5 gm.; germinating immediately upon maturity. Highly susceptible to
cercospora leaf spot.

Beattie (9) lists the following varieties grown commercially in the

Figure 23.—An +1 order, cotyledonary lateral branch of one form of Valencia.
The »+J branch produces »+ 2 reproductives at its lowest nodes, then
several 2 + 2 vegetatives, finally the upper nodes produce 2+ 2 reproductives.
All the nodes of the n + 2 vegetatives bear » + 3 reproductives which terminate
the branching system. ;

MORPHOLOGY, GENETICS AND BREEDING 69

Figure 24—An n+ 1 order, cotyledonary lateral branch of a Valencia form. In this
form the peanut branching system is reduced to the n order main stem and four
n-+1 order vegetative branches. Two of these arise from the cotyledonary
node and two from the next two main stem nodes. All further » + 1 nodes and
all »+2 nodes bear reproductive branches which terminate this branching
system.

70 THE PEANUT—THE UNPKEDICTABLE LEGUME

United States. They are shown here as they could occur if classified by
the foregoing system.

1. Virginia Runner — Prostrate
2. Jumbo Runner _ oy
3. N.C. or Wilmington Runner —- " — Virginia
4. African — ie
5. Virginia Bunch — Erect
6. Spanish — Erect
7. Improved Spanish _ Me — Spanish
8. Small Spanish _— e,
9. Tennessee White _ ‘a
10. Tennessee Red — me — Valencia
11. Valencia _— oe

If this scheme of classification based upon the orders and patterns
of branching were generally employed, the understanding of reported
experiments, not only in breeding, but in essentially all other types of
peanut research would be greatly facilitated. Where original varietal dis-
tinctions have been obliterated through crossing and segregation, the
parentage and a brief description in the above terms would furnish the
needed information. Prevot (54) has already indicated the relationship
between branching habit and the problem of fertilizer treatments with
peanuts. It is obvious, however, that this relationship could not be the
same for both Spanish and Virginia peanuts.

GENETICS AND BREEDING

The problem of the improvement of peanuts through selection is not
a simple one. The peanut is a plant which is, in our experience, for all
practical purposes 100 percent inbred, difficult to cross, and productive
of so few seeds per plant that the recovery of improved types in small se-
gregating populations is rendered highly improbable. Consequently to-
day’s peanut breeder must not only increase the precision of estimating
genetic differences within segregating populations, but also must over-
come the sterility barriers between the various species of peanuts, gather
fundamental biological information on the structure and physiology of the
peanut and its relatives, and relate these to the problem of improvement
through selection.

The reproductive behavior (i.e. self-pollination) of peanuts is such
that new forms tend to be preserved and isolated from one another.
Nevertheless there has been hardly a breeder from the time of Van der

MORPHOLOGY, GENETICS AND BREEDING 71

Stok (74) to the present, who has not been able to isolate distinct
strains from within varieties. The’ question of selection within varieties
as opposed to selection within hybrid populations has claimed the at-
tention of peanut breeders. Men with long experience have maintained
that pure lines of peanuts tend to break down if selection pressure is re-
laxed. The instability of the pure lines may have arisen from (1) acci-
dental seed mixture (2) natural outcrossing, or (3) chromosomal insta-
bility. The first possibility need not be discussed. According to Kushman
and Beattie (42) natural hybridization occurs with low but significant
frequency. In experiments designed to clarify this point numerous cases
in which crossing had occurred between Spanish and Valencia peanuts
were studied. The observed segregation of seed coat colors followed the
expected pattern. Three years of work demonstrated a small but definite
amount of natural crossing. Critical experiments of this nature have not
been conductive ive by other workers so this is the only reliable published ac-
count. In contrast, the present senior author has observed the consistent
uniformity of hundreds of F, and F, plant progenies. These have included
many diverse families from experimental crosses grown side by side. If
further experimental evidence confirms the opinion that pure lines of pea-
nuts are unstable in the absence of selection pressure, this will be in
harmony with the known behavior of peanut chromosomes. Husted (38)
observed multivalent chromosome associations at first meiotic metaphase
and concluded A. hypogaea was a tetraploid. Mendes (44) confirmed
this in 1947. The number of chromosomes in cultivated peanuts is 2n =
40 while some of the wild species examined have 2n = 20, observations
which the writers have also made. The irregularities reported by Husted
(38) provide ample basis for predicting sporadic segregation from culti-
vated strains.

Notwithstanding the fact that peanuts were subjected to genetic study
by Van der Stok (74) as early as 1910, only limited progress has been
made in the improvement of peanuts through breeding. With the advent
of World War I interest in peanuts as a source of vegetable oil stimulated
peanut-breeding activity. Thus in the United States reports of breeding
work began to appear about 1918, Beattie, private correspondence). Al-
though the U.S. Department of Agriculture continued its efforts through
the third decade of this century, active work at the various State experi-
ment stations did not begin until near its end. Breeding programs have
been reported as starting in Georgia in 1931, in Florida in 1928, in North
Carolina in 1929, During these years most of the work in Virginia, North
Carolina and South Carolina consisted of making individual plant selec-

72 THE PEANUT—THE UNPREDICTABLE LEGUME

tions from among existing stocks of peanuts. The programs in both
Florida and Georgia appear to have developed from selection within
hybrid populations from varietal crosses. Meanwhile reports from India
(1), the Philippines (24, 49, 56, 61, 62), the Dutch East Indies (12),
French West Africa (16) and elsewhere continued to reach this country.
Breeding programs have been in existence in the U.S. Department of
Agriculture for 30 years, in State experiment stations for 20 years, and
for similar lengths of time in various foreign countries. At present some
effort is being expended toward peanut improvement through selection in
nearly all warm temperate and tropical countries.

Despite the great effort put forth in various countries of the world
little success has been achieved in peanut breeding. The products of these
researches are not, by and large, the plants which fill the commercial
fields ; or if they are they have not.raised to any degree the average output
of the areas where released. For example, the average production per acre
in the Virginia-Carolina area continues at about 1,100 pounds per
acre, notwithstanding the sporadic “improvement” announcements of the
past 30 years. During these same years, while the spring wheat industry
of the United States and Canada was saved by breeding and pathological
researches, and corn production was revolutionized by breeding, the “im-
proved” selections of the peanut breeder have continued to maintain the
low State average yields (figure 25).

As yet we can only surmise the biological explanation of Bouffil’s
(13) statement that the hybridization of peanuts has been attempted but
that up to the present no positive results have been obtained ; or of Darl-
ington’s (20) declaration, in reviewing Mendes’ (44) cytological work,
that perhaps this will open the way to improved varieties from interspe-
cific crosses in this plant, which hitherto has been so unresponsive to im-
provement through the ordinary methods of cross-pollination and selec-
tion.

While there is no doubt that peanuts are difficult material, the inde-
pendent and isolated attempts of the various workers on the problem
have been a contributing factor to the slow progress made in this field.
It is misleading to take too seriously the comparison of 30 years’ research
on wheat and corn with the unconnected reports on the peanut over the
same period. Few cross-references exist in the literature on peanuts, each
man having gone his independent way. Thus there have resulted needless
repetitions of effort and the consequent elementary nature of experiments
evident in all the literature. The combination of the lack of knowledge, or
the possession of erroneous information on the biological nature of pea-

MORPHOLOGY, GENETICS AND BREEDING 73

1550
CORN Nortn Carouina

1400L

1200.

L. PEANUTS Va.,N C.,TENN.

1000)

POUNDS PER ACRE

800L

q PEANUTS S.C.,Ga,,Fua.,
600L Ata., Miss.

400L._1 1 1 1 1 n 1 1 poy 1 1 1
8-22 20-24 22-26 24-28 26-30 28-32 30-34 32-36 34-38 36-40 38-42 40-44 42.46 44-48
19-23 2-25 23-27 25-29 27-31 29-33 31-35 33-37 35-39 37-41 39-43 41-45 43-47

MOVING 5-YEAR INTERVAL

PEANUT YIELD 1918-1948

MOVING 5-YEAR AVERAGE

Figure 25.—Thirty years of peanut production in the southeastern United States.
The light line shows corn production in North Carolina during the same period.

nuts with the disparate nature of the breeding experiments conducted, is
sufficient in itself to render success improbable.

In reporting the published works on peanut breeding and genetics
we have been unable to unfold a sequence of events or to build a co-
ordinated body of knowledge culminating in recent advanced studies
logically derived from the results of previous experiments. Instead we
have attempted to preserve the mosaic of unrelated patterns and have
organized them only to the extent of presenting first, a summary of
breeding techniques ; second, inheritance studies ; third, disease resistance ;
and fourth, breeding.

TECHNIQUES

(a) Cross-pollination

Badami (1) made the following observations with respect to the tech-
nique of crossing ‘peanuts: The pollen sacs burst about sunrise on warm
days, fertilization is completed within 30 hrs,*, flowers droop in 24

*It is known to occur in 12-16 hrs; see “Reproductive Morphology’’.

74 THE PEANUT—THE UNPREDICTABLE LEGUME

hours, wither in 48 hours, pegs elongate in 72 hours, visibly so in 4 or 5
days, and complete development of fruit and seed takes about 60 to 62
days from fertilization. Badami emasculated the flowers from 5 p.m. to
midnight and pollinated them between 6 and 7 a.m.

According to investigations of Stokes and Hull (69) the stigma is
buried among dehisced anthers in the tightly closed keel of the mature
flowers. The flowers are fully opened before dawn, the anthers dehisced.
The flowers wither the day of anthesis and fertilization does not hasten
withering. The flowers were emasculated between 10 and 11 p.m. Acci-
dental pollination was considered unlikely. Thrips were about the only
visitors in the greenhouse. Pollinations were made between 8 and 10 a.m.
and were about 50 percent successful. The cross-pollinated flowers were
labelled by means of a thread attached to the flower and later transferred
to the peg. Plants were cultured in 4-gallon stone jars and kept pruned
back. Fruiting inhibited flowering and flowering could be induced by
removing the fruits.

Umen (73) used the technique of removing all the flowers from the
inflorescence except the one to be cross-pollinated. In this manner the
first flower of an inflorescence could be used, the remainder removed.
When this is the case the probability of successful development of the
fruit is greater and the opportunity for mistaken identity of the cross
almost eliminated. Emasculation was done with forceps between the
hours of 2 and 8 p.m. the day before the flowers were to open. Bagging
the emasculated flowers was found to be unnecessary. The pollinations
were made early the next day. The plants were grown in pots.

Patel et al. (48) emasculated the buds between 5 and 6 p.m. The re-
sult was checked by a hand lens. Pollination was effected between 7 and
8 a.m. Ten to 30 percent of the pollinations were successful. The flowers
were not bagged. The plants were grown in large pots. The crosses were
marked by different colored threads. After 4 to 5 days the thread was
transferred to the peg.

(b) Vegetative propagation

Many things coordinate the forces of adversity on the would-be
peanut breeder. Only a few hours are available for emasculation each
day and these fall at the rather inconvenient time when ordinary men are
preparing to go to bed. It should be added that each emasculation con-
sumes several minutes so that the total for an evening’s work is rather
small. Some alleviation of this difficulty is obtained by the propagation
of peanuts from cuttings. The number of plants grown from each hybrid
seed can be much increased by use of this technique. Sufficient work

MORPHOLOGY, GENETICS AND BREEDING 75

has now been done with cuttings to permit the employment of F, testing
should this seem to be desirable in peanut breeding. Gregory conducted
replicated F, trials of peanuts from cuttings in 1945 with sufficient suc-
cess to show the reliability of this method of propagation.

The first work recording the use of cuttings as a tool in varietal ex-
perimentation with peanuts was reported by Guerrero (28) who, on the
Island of Guam, made the first recorded comparison of yields of nuts and
forage per acre of peanuts from cuttings and from seed. It is obvious from

‘the limited data given that the experimental error was very large. No
further work has been reported from this source. Rodrigo (61) became
interested in the use of cuttings as a means of propagation to escape the
problem of seed deterioration common to the Philippines. His seed
germination averaged 94.7 percent and 89.7 percent of the cuttings rooted.
The following table gives some of the comparative figures on developed
pods, undeveloped pods, and pegs without pods at harvest for three
different varieties :

Number of:
Variety Propagating
Name Materials Developed Undeveloped Stipes
Pods Pods Without Pods
Kinorales seed 26.10 1.15] 11.90 + 0.67] 20.40 + 1.59
Kinorales cutting 23.30 + 0.89} 13.90 + 0.64] 33.10 + 2.04
Lemery seed 19.20 + 1.21] 10.70 + 0.92] 15.00 + 2.11
Lemery cutting 18.00 + 0.96} 8.60 + 0.70} 27.00 + 2.32
Valencia seed 23.40 + 0.94) 13.90 + 0.99 | 18.30 + 0.94
Valencia cutting 14.40 + 0.73] 10.10 + 0.74] 13.70 + 0.87

Rodrigo pursued the problem of yield from cuttings further. Cuttings
were taken from three varieties when the plants were 2, 3, and 4 months
old. This experiment was badly hit by ants and drought so that no com-
parison could be made between seed and cuttings; of the cuttings, how-
ever, the 3-month-old plant cuttings gave the highest percentage rooting
while the 2-month-old plant cuttings gave the greatest production of
forage and seed.

Gregory (26) found that rapidly growing plants just prior to flower-
ing produced highly successful cuttings. It should be noted, however, that
the total number of cuttings per plant under these circumstances is much
smaller than from older flowering specimens.

Harvey and Schultz (29) compared the yields of plants from cuttings
of main stems and laterals with the yields of plants from seed. It will be
recalled that the peanut produces a single main stem, primary laterals,

76 THE PEANUT—THE UNPREDICTABLE LEGUME

and other lateral branches. The test was planted in a split plot design
where the sources of plants were the subplots (main stem, lateral branch,
or seed) and the three varieties used were the whole plots. No significant
differences in yield were found between the two sources of cuttings. The
yields of plants from seed were significantly less than those of plants
from main stem cuttings but not less than those from lateral branch
cuttings. The seed were planted the same day the rooted cuttings were
placed in the field, but the plants from seed may not have been strictly
comparable in developmental stage to the cuttings. The following table
shows the results obtained :

Yields of Peanuts in Pounds/Acre

Lateral Main Average

branch stem Seed for strain
N.C. Sel. 32....... eee 1,237.8 1,514.4 890.0 1,193.9
Martin Co. Runner...... 1,002.5 1,281.6 1,173.9 1,132.4
Spanish2B.............. 1,127.6 1,026.7 1,028.1 1,101.0
Av. for source of plants... 1,122.3 1,274.6 1,030.0

Beattie e¢ al. (8) concluded after some years’ experience that the
optimum plot size for testing varietal differences in peanuts was a single
100-foot row or five to six 20-foot rows. Robinson et al. (60) investigated
optimum plot size from uniformity data. Their conclusions, briefly sum-
marized below, are perhaps the most reliable information to be had on
this subject. The uniformity data were handled in terms of decreasing co-
efficients of variation with increasing plot size. The following diagram
gives the pertinent results:

MORPHOLOGY, GENETICS AND BREEDING 77

AVERAGE CoEFFICIENTS OF VARIABILITY FOR DiIFFERENT PLot DIMENSIONS WHERE
REPLICATIONS CONSIST OF 6 ASSUMED VARIETIES.

16 |—

15 j— . 123-1 (Length and number of units per plot)
ES 14 |—
= 13 |—
8 124-2
s a 25-1
S 12
> 11 jJ—
~ Ag-3
8 10 |— .374-1
& . 25-2
8 9 |— 50-1
S .37-2

3 |— 125-3

.374-3
Ti 50-2
. 50-3
fig teh ih ae fie eh at

1 2 3 4 5 6 7 8 9 10 11 12
Plot Size (Number of 124-foot single-row units)

INHERITANCE STUDIES

Van der Stok (74) reported that red testa and light red testa segre-
gated three dark red to one light red in the F,. Badami, Hayes, Hull,
Patel e¢ al., and Stokes and Hull (1, 30, 36, 48, 69) have studied the
inheritance of various characters in the peanut. Hull (36) summarizes

the genetic results which had been published by 1937. His summary fol-
lows :*

“1. Red seed dominant to russet or tan (3:1), Van der Stok (74), Badami (2),
Stokes and Hull (69), Hayes (30). Four colors purple, red, rose, and white,
with genes Pp,Rdrd, Riri, Rere, Patel (48).

2. Prostrate habit dominant to erect, two factors, Badami (2); (15:1) Hayes
(30) ; duplicate genes, Patel, (48).

3. Chlorophyll; three factors with triple dominant dark green and triple re-
cessive albino, Badami (2) ; two genes, Patel (48).

4. Dark red stem dominant to light red (3:1), Hayes (30). Violet tinge domi-
nant, appears to be associated with hardiness, Badami (2). Purple stem, dup-
licate genes, Patel (48).

5. Long seed dominant to short (15:1), Hayes (30).

6. Fertile dominant to sterile, complementary (15:1), Hayes (30).

7, Normal leaf dominant to crinkled leaf, complementary (15:1), Hayes (30).

* This is quoted exactly except that the present writers have altered the reference numbers so
that they now correspond to the references cited at the end of this chapter.

THE PEANUT—THE UNPREDICTABLE LEGUME

. Leaf rachis presence dominant to absence, complementary (15:1), Hayes

(30).

. No constriction on pods, double dominant, two factors, Badami (2).

. Leaflet size intermediate in Fy and wide range in Fe, Badami (2).

. Large pod dominant to small, three factors, Badami (2).

. Pericarp thickness, five factors, thin pericarp linked with pygmy seed,

Badami (2).

. Deep reticulations on pericarp dominant to shallow, at least four factors,

Badami (2).

. Hairy stem dominant to less hairy, Badami (2) ; 3:1, Patel (48).
. Three or many-seeded pods dominant to less than three-seeded, at least three

factors, Badami (2).

. Long growing season dominant to short, Badami (2); 3:1, Patel (48).

. Early fading flowers dominant to late, Hayes (30).

. Deeply colored corolla dominant to light, Hayes (30).

. Red color on leaflet vein dominant to its absence, Hayes (30).

. Sine leaf shape dominant to Valencia shape, Hayes (30).

. Required rest period of seeds partially dominant to its absence, Stokes and

Hull (69).

. Variegated seed due to rupture of seed coat as found in A. namby quarae

partially dominant to its absence in A. hypogaea, Stokes and Hull (69).

. Sterile dwarf, 15:1, Patel (48).
24,

Branching over non-branching, 3:1, Patel (48).”

Hull’s own work was chiefly directed toward analyzing the genetic
behavior of dormancy in peanut seeds. In addition, however, he reported
the following results on other characters:

*A,

In crosses of Spanish and Runner peanuts long by short seeds were intermedi-
ate in the hybrid. The results indicated that seed shape was largely con-
trolled by physiological maternal influence rather than by embryo genotype.

. Russet seed coat of Runner peanuts dominant to tan in Spanish.
. Yellow seedlings from certain crosses behaved as full recessives in a duplicate

gene complex with green fully dominant. The assignment of genetic formulae
with respect to this character cuts across some interesting taxonomic lines,
for Hull states that the following genetic formulae and varietal association
was indicated from his study of this character: LiLilgl2g (Spanish) LiIyIele
(Runner group and A. nambyquarae and LiLyLeLle (Valencia and A.
Rasteiro*.) ‘i

. Valencia plant type was found in the progenies of several crosses of Spanish

x runner. It behaved as a recessive set of duplicate genes where each parent
carried alternate recessive and dominant pairs.

. Male sterile brachytic dwarf appeared in the progeny of Virginia Runner x

Tennessee Red and behaved as a simple recessive.

. The regressions of twenty-two separate characters as dependent variables, and

rest period of seeds, seed shape, seed coat color, yellow seedlings, and Valencia
plant type as independent variables were analyzed. No significant regressions
were found.

Rasteiro=a form of A. hypogaea.

MORPHOLOGY, GENETICS AND BREEDING 79

Hull measured the rest period in peanut seeds in terms of average
time to emergence with seeds planted as soon as possible after harvest. In
the Spanish and Valencia groups this time ranged from 9 to 50 days,
while in the more dormant group which includes runners, A. namby-
quarae, and A. Rasteiro it ranged from 110 to 210 days. Hull makes the
additional statement that, ‘“Peanut seeds planted soon after maturity in
conditions near optimum for germination frequently required rest periods
ranging up to 2 years before germination.” Hull assumed a multigenic
control of what he called “seed condition necessary to rest” with a normal
frequency distribution. He supposed that at about the midpoint of the
range of seed condition the threshold for germination was attained. Such
a situation would explain the marked skewness to the left of his frequency
distribution of days from planting to emergence.

Since the publication of Hull’s summary, Higgins (31, 32) has re-
ported further inheritance studies. He analyzed the genetics of seed coat
color in peanuts. Three basic colors were recognized: Red, white, and
flesh. These were further characterized as follows:

1. Flesh—Base color is a salmon flesh, pale to dark, reddish lilac markings about

the hilum and along the veins, sometimes spreading. Varieties: Spanish, N.C.
Runner (African), Virginia Runner, Virginia Bunch.

2. Red—This color also includes salmon lilac, various purples, and slate violet.
3. White—Philippine White and Pearl are greenish white to lilac white which
weathers to yellow white.
Red x Flesh Flesh x White (Philippine White)
Fy all Red F all Flesh
Fo 3 Red: 1 Flesh Fp, 15 Flesh: 1 White
White (Pearl) x Red
Fy all Red

Fo 12 Red: 3 Flesh: 1 White

White (Pearl) x White (Philippine White)
Fy all Red

Fo Red, Flesh, and White

The numbers were too small in the white x white progeny to establish
the genetic basis with certainty, but the following suggested formulae
appear to explain the results obtained:

Pearl RRFyFyFoFs didy dodo
Phil. White rrfyfyfofe D,D1DeDe

It is obvious that there are at least duplicate factors for flesh, an ad-
ditional factor which produces red in the presence of both flesh factors,

and two factors for color development, the absence of either of which
results in white.

80 THE PEANUT—THE UNPREDICTABLE LEGUME

DIsEASE RESISTANCE

Varietal resistance of peanuts to sclerotium wilt or southern root rot
has been reported by Reyes (56). From experiments conducted in the
Philippines Reyes concluded: “Different varieties of peanuts grown in
an infected field showed varying degrees of infection. Wilting ranging
from 31.3 to 50.7 per cent of the plants was noted by actual counts.

“Varieties used in field inoculation tests showed susceptibility to
peanut wilt in the descending order as follows: (a) Valencia; (b) Maca-
pno; (c) Georgia Red; (d) White Improved Spanish; (f). Biit; (g)
Cagayan No. 1; (h) San José No. 3; (i) Vigan Lupog; (j) Tirik; (k)
Tai-tau; (1) Virginia Jumbo; and (m) Virginia Jumbo (a). The least
infected varieties were Virginia Jumbo (a), Virginia Jumbo, and Tai-tau
while Valencia and Macapno were the most seriously infected.”

Bolhuis (12) stated that A. Rasteiro, A. nambyquarae, and Schwarz
21, a selection from native sources, were highly resistant to the slime,
disease (Bacterium solanacearum). Higgins (31) stated that resistance
to each of the two leaf spotting fungi is inherited separately and suggested
that a single factor is involved in each case. With respect to resistance to
Sclerotium rolfsit this author stated that ‘most of our selections show
a high degree of resistance.” Reyes and Romasanta (57) reported varia-
tions in susceptibility among 16 different varieties to Cercospora
personata. The intensity of infection was measured by leaf spot count
from a duplicated trial. It was suggested that resistance to this disease
might be attained through breeding.

BREEDING

In 1910 Van der Stok began the breeding work with peanuts in the
Netherlands East Indies. In 1938, Bolhuis gave the following as princi-
pal objectives in the breeding program: high yield, resistance to slime
disease, erect foliage, large seeds, pods with more than two seeds, pods
with slight constriction, and early ripening.

Badami (1) reported his initial hybridization results with peanuts in
1922 and in later annual reports from the Mysore Agricultural Depart-
ment he has indicated the results of subsequent selection.

Patel ef. al. (48) reported in 1936 that a breeding program had been
been in progress in Madras for about 5 years. Approximately 100 varie-
ties were grown in the two annual seasons, irrigated (February-June),
“rain-fed” July-January).

The economic importance of peanuts, their world production, and a

MORPHOLOGY, GENETICS AND BREEDING 81

short history of their cultivation in the U.S.S.R. were reported by
Piroznikova (51). A description of the peanut, its types, varieties, and
various characteristics were included. Extensive data are presented on
variety trials in various regions of the U.S.S.R. The main aims stated for
the breeding program for U.S.S.R. are earlitiess, drought resistance,
disease resistance, high oil content, high protein content, and a production
of a plant suitable for mechanical harvesting.

From Krasnodar, Umen (73) described the necessity of understand-
ing the floral biology of the peanut. He stated that pure line selection
started in 1926 had shown hybridization to be the only promising method
for improvement of the peanut. To quote from the abstracting journal,
“The method of pure line selection has not yielded very favorable results,
especially in regard to resistance to Fusarium and hybridization is re-
garded as essential.”’

Selection for improved varieties of peanuts has been attempted in
French West Africa since 1924. Many criteria for selection have been
used without success. The morphological character of the pods and the
weight per 100 seeds are now the principal characters selected. An exten-
sive series of local strains collected from the native farms is grown at the
central station. The selections are made but are subsequently increased in
the locality where the original strain is grown and known to be adapted.
Hybridization, either natural or artificial has yielded no results of con-
sequence to the French West African program. Bouffil has not entirely
abandoned the idea of the use of hybridization in peanut breeding but
feels that the existing stocks of peanuts in French West Africa must first
be purified.

In the United States, prior to 1930, the most extensive work on the
breeding of peanuts was reported from Florida by Stokes and Hull (69).
Single plants were selected from within an unselected variety, Florida
Spanish, seven of which were tested for 8 years. Some showed increases
over the original variety averaging 22.8 percent. It was concluded that
plant-to-row selection produced high-yielding strains. No heterosis was
observed in the various hybrids made.

Hull and Carver (37) have continued this work, and in 1936 pub-
lished a summary of their breeding procedures. These workers concluded
that the desired types could “hardly be obtained except by hybridization.
.. . It has also appeared that large numbers of hybrids would be neces-
sary to provide reasonable chances of obtaining the desirable types.”

In Georgia an extensive breeding program is under way with a col-
lection of varieties and strains with objectives to combine high yield,

82 THE PEANUT—THE UNPREDICTABLE LEGUME

quality, and oil of Spanish peanuts with disease resistance and nonsprout-
ing of the bunch and runner types.

Results of variety yield trials for the years 1929, 1930, and 1931 were
reported for the Holland, Virginia, Station by Beattie and Batten (7).
This work was mainly directed toward increasing seed size. It was con-
cluded that at least seven strains of Virginia type peanuts had inherent
qualities of extra large seed.

In 1943, Batten (5) reported regarding the selection work at the
Virginia Station: “The idea has been to develop a strain which would
produce a high percentage of extra large kernels, 30 to 32 per ounce.”
The method of breeding has been confined to single hill selection without
prior hybridization. The breeder stated that these selections behaved as
pure lines. Batten (6) announced the release of two improved selections
in 1945. The following table presents comparisons of these strains with
a local commercial variety :

A CoMPARISON OF YIELD AND GRADE OF Two NEw STRAINS OF PEANUTS WITH A
COMMERCIAL VARIETY

Vield pea ie Kernels | Value
Un- Meat Extra per per
shelled Shelled Large ounce acre

Pounds | Pounds | Per cent | Per cent | Number

Holland Jumbo......... 1945 1323 68.0 53 27 $182.44
Holland Virginia Runner.) 2262 1698 75.0 27 37 $223.01
Commercial Jumbo..... 1695 1170 69.0 35 30 = [$157.30

Beattie, in private correspondence with one of the writers, stated:
“Peanut Improvement by Selection: All this work has been carried on in
cooperation with the State experiment stations in South Carolina, Vir-
ginia and Georgia. Dating back to 1918 and using individual hills as
starting points, a number of high yielding, desirable quality strains have
been developed. Spanish 18-38, Improved Spanish 2-B, and several
strains of the large-seeded Virginia type are examples. Spanish 18-38 in
particular has attained considerable commercial importance in most parts
of the peanut-producing area.”

Since 1945 the North Carolina Agricultural Experiment Station has
been conducting research on the nature and extent of effective variation
in populations from peanut hybrids. These experiments have been de-
signed to indicate what, if any, breeding opportunities exist following the
varietal crossing of peanuts. Preliminary results from this work show that

MORPHOLOGY, GENETICS AND BREEDING 83

the total genetic variability in segregating populations of peanuts is large
enough to make possible a selection advance beyond the mean of the
original population. The prior conclusions of Umen and of Hull and
Carver regarding the necessity of hybridization for the success of prac-
tical peanut breeding are fully supported by these data. The contrary con-
clusion reached by Bouffil suggests, however, that further exploration of
the problem is justified.

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1933. (WHAT HAS BEEN DONE IN GROUNDNUT BREEDING). (TECHNIQUE OF
ARTIFICIAL HYBRIDIZATION IN Arachis). (BIOLOGY OF PEANUT
FLOWERING). Lenin Acad. Agr. Sci., Inst. Sci. Res. Oil Cult. Kras-
nodar, No. 5:8-12, 29-33; No. 6:1-57. (Cited from Plant Breeding
Abstracts. 5:60.)
(74) VAN DER Stok, J. E.
1910. ONDERZOEKINGEN OMTRENT, Arachis hypogaea L. (KATANG-TANAH).
Med. van het Dept. Land. 12:176-221. (Cited from Hull, 1937).

88 THE PEANUT—THE UNPREDICTABLE LEGUME

(75) WaAtpRon, R. A.

1919. THE PEANUT (Arachis hypogaea)—1TS HISTORY, HISTOLOGY, PHYSIOLOGY,
AND UTILITY. Penn. Univ. Bot. Lab. Contrib. 4:301-338.
(76) YARBROUGH, J. A.
1949. Arachis hypogaea. THE SEEDLING, ITS COTYLEDONS, HYPOCOTYL AND
roots. Amer. Jour. Bot. 36:758-772.

(77)
1950. Arachis hypogaea, SEEDLING GROWTH RATE. Amer. Jour. Bot. 37:(in
press). :

CHAPTER IV

PHYSIOLOGY AND MINERAL
NUTRITION

i HENRY C. HARRIS AND ROGER W. BLEDSOE’

The subject of this chapter is so broad in scope and so detailed that its
treatment necessitates a limited discussion of any particular topic. In a
limited space the authors have attempted to cover most contributions, al-
though some foreign publications are inaccessible (23, 24, 25) and un-
doubtedly others have been omitted unavoidably since the data are pre-
sented in many languages.

Various aspects of plant physiology have advanced considerably in
recent years, yet the application of that knowledge to the solution of
problems associated with the peanut plant has been much neglected and
little organized work has been done. After reviewing the work, the
writers have the impression that greater clarity and new information
might be gained by applying more precise methods in planning experi-
ments and in evaluating experimental results. Some authors do not in-
clude enough experimental data to enable others to repeat experiments
described. Frequently contributions deal with questions of local im-
portance. Other papers merely emphasize the inconsistencies of yields
from fertilizer trials without attempts to explain why such occurred. Some
problems, namely, the absorption of ions by the gynophore or developing
fruit and the necessity of such for fructification, have received consider-
able attention in recent years. To some extent, agreement has been
reached on the essentials of that problem. Many phases of physiology of
the peanut plant have been omitted due to the absence of published data ;
other phases are discussed briefly since they are assumed to be similar to
that of most plants as given in general references (41, 50, 56, 60).

ay
1Henry C. Harris and Roger W. Bledsoe are agronomists, Florida Agricultural Experiment
Station.

90 THE PEANUT—THE UNPREDICTABLE LEGUME

GENERAL CHARACTERISTICS
Foliage

The peanut is a low-growing, annual, herbaceous, leguminous plant
with one upright central stem (63, 68, 88) and numerous lateral branches,
the lower of which may branch several times. The varieties are fairly
well separated into the bunch and runner types. Lateral branches of
bunch peanuts are more or less upright, while those of the runner type
tend to be more prostrate. The central stem is usually taller in the more
erect varieties. The leaves are compound, pinnate, consisting of two
pairs of nearly equal leaflets, on a slender petiole of moderate length.
The leaflets show nyctitropic movement and tend to orient themselves
so as to intercept the greatest amount of light. So far as the writers
know, measurements of the total leaf area of peanuts have not been made;
however, the area would appear to be relatively large and well suited to
photosynthetic activity. The leaves are moderately pubescent, which
should aid in the retention of dust and sprays. During the latter part of
the growing season there is often a progressive defoliation of leaves from
the base toward the stem tip. While such defoliation might be associated
with disease or nutritional deficiencies, there is a natural tendency for
loss of leaves accompanying plant maturity.

The rate of leaf and flower appearance as recorded by Mohammad,
et al. (58), is shown in table 1.

Maximum increase of leaf and flower appearance occurred with the
bunch peanuts (Japan and Spanish) during the interim of 56 to 97
days after planting and from 70 to 125 days after planting with the runner

Table 1.—AVERAGE INCREASE IN NUMBER OF LEAVES AND FLOWERS PER PLANT
DvuRING DIFFERENT PERIODS OF GROWTH.

Average fortnightly increase in number of leaves and flowers
per plant between 42 and 154 days after seeding

42- 56- 70- 84- 98- | 112- | 126- | 140-
55 69 83 97 | 111 | 125 | 139 | 154

Variety Organ

Small Leaves 19 51 99 87 37 16 0 0
Japan Flowers 9 39 103 96 91 28 2 0
Small Leaves 15 76 92 71 27 10 0 0
Spanish Flowers 12 75 | 192 | 175 | 118 55 15 0
Burmese Leaves 17 76 80 98 64 44 32 26

Flowers 3 37 80 | 154 | 233 | 136 73 32

PHYSIOLOGY AND MINERAL NUTRITION 91

type (Burmese). The fresh weight of the green shoots at 140 days was
about 96 percent of the whole plant. Others (10) have found a similar
relationship.

Flower, Gynophore and Fruit

The fruiting parts of the peanut plant have been of special interest
to a number of investigators (10, 37, 45, 63, 68, 74, 81, 88, 90, 91).
Botanists have known for more than a hundred years that the flowers
were of one kind and complete, and yet the idea still persists, according
to the literature, that peanuts produce two kinds of flowers. Flowers are
borne in the leaf axils and one or more may appear in the same axil.
They appear first at approximately 50 days after seeding and then daily
throughout the flowering period. The orange-yellow flowers are fully
open in early morning and usually begin to wither and die by noon of the
same day. Therefore, an accurate record of flower production may be
obtained.

Shibuya (74) found the length of the flowering period to range from
69 to 93 days with the bunch type. That period was 74 days in one experi-
ment with the runner peanut. Maximum flower production occurred 50
to 60 days after the first flowers appeared. The bunch peanut produced
approximately 600 flowers; the runner, approximately 1,000. However,
there was considerable variation between individual plants.

Some data of flower production by the Dixie Runner peanut at the
Florida Station (10) are given in table 2. Plants produced an average of
644 flowers during a period of about 80 days when grown in sand culture
with the complete nutrient solution applied to both rooting and fruiting
zones (table 2). An unbalanced nutrient supply had a pronounced effect
on flower production, and blossoming virtually ceased when the root
treatment of the plants was changed from a complete nutrient solution
to distilled water. The results shown in tables 1 and 2 and others obtained
by Shibuya (74) indicate that the runner peanut has more flowers than
the bunch and that the flowering period ranges from 2 to 3 months or
longer.

The gynophore or peg is usually noticeable within 7 days after the
flower is fertilized. It is formed by division and elongation of cells back of
the ovaries. The organ is geotropic and by elongation it transfers the
ovaries from an aerial to a hypogeal position. Elongation generally ceases
after the gynophore has penetrated the soil to a depth of approximately
2 inches. Then rapid embryo development usually starts within 10 days,
and the fruit is mature at about 60 days after the appearance of the flower.

92 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 2.—MEAN FLOWERS PER PEANUT PLANT (VARIETY Drx1E RUNNER) AS
AFFECTED BY NUTRIENT TREATMENT. Roots or PLANTS GROWN IN COMPLETE
SOLUTIONS To JuLy 1 (80 Days) AND DEFICIENT SOLUTIONS To AuGust 20 (50 Days).

Flower production per 10-day interval | Mean | Mean

*The negative sign indicates the element was omitted from the nutrient solution.

When the gynophore fails to contact the soil, its length rarely exceeds |
6 inches, and then it eventually withers. The above-ground portion of the
peg has a stem-like anatomy, while the underground portion has a root-__
like behavior and numerous epidermal outgrowths may be present (fig-.
ure 1). The young fruit is fleshy in nature and the shell of the fruit some-
times has root-hair-like formations (81, 88, 90, 91). These characteristics
of the fruiting organ suggest that it might absorb water and nutrients. .,,

Courtesy Florida Agricultural Experiment Station

Figure 1—Gynophore with root-hair-like outgrowths.

PHYSIOLOGY AND MINERAL NUTRITION 93

A high percentage of the flowers produce pegs. Shibuya reported that
about 70 percent of the flowers of bunch peanuts and 75 percent
of those of the runner peanuts produced pegs, while with the Dixie
Runner variety 58.7 percent of the flowers produced pegs when plants
were grown in sand culture (10).

Shibuya reported that 23 percent of the flowers of the bunch type and
9 percent of flowers of the runner type produced fruit (mature and im-
mature) with an average of 45 fruits per plant for each type. Results at
the Florida Experiment Station (10) show that 9.2 percent of total
flowers resulted in fruit formation, while 24.4 percent of the pegs which
entered the fruiting medium produced fruit when plants were grown in
sand culture. In a similar experiment 17 percent of the gynophores of
runner peanuts grown in a complete nutrient solution (37) produced
fruit. Individual plants varied considerably, but the percentage of flowers
effective in producing fruits was small. The nutrient supply of the plant
(10, 37) influenced the effectiveness of the flowers and pegs in the pro-
duction of fruits (figures 2, 3). Calcium, particularly when deficient in
the pegging zone, gave a low percentage of fruit (figure 4).

Courtesy Florida Agricultural Experiment Station

Figure 2—Dixie Runner peanut plant which received a complete nutrient solution in
both the rooting and fruiting zone.

94 THE PEANUT—THE UNPREDICTABLE LEGUME

Courtesy Florida Agricultural Experiment Station

Figure 3.—Dixie Runner peanut plant which received a complete nutrient solution
in the rooting zone and distilled water in the fruiting zone.

The peanut fruit may have one, two or more seed. It has been stated
(4) that with fruit of those varieties which normally produce two seeds
7 percent of the ovules fail to be pollinated and that an additional 10 per-
cent of the ovules abort during the early growth period, resulting in about
17 percent of the fruit being one-seeded.

The majority of mature fruit are located usually on the basal portion
of the lowest branches, and results of Middleton and Harvey (55) in-
dicate that there is a tendency for immature fruit and “pops” (fruits with
aborted embryoes) to occur farther out on the branches.

Roots

The peanut plant has a well-developed tap-root system, similar to
that of beans or peas, with numerous lateral branches extending a con-
siderable distance in the soil. Several workers (17, 58, 63, 68, 88,) have
made a careful study of the root system. The soft, fleshy, fragile roots col-
lapse and dry quickly when removed from the soil. This tends to give the
impression that the root system of the peanut is relatively small.

PHYSIOLOGY AND MINERAL NUTRITION 95

Courtesy Florida Agricultural Experiment Station

Figure 4.—Dixie Runner peanut plant which received a complete nutrient solution
in the rooting zone and a calcium-deficient solution in the fruiting zone (Plant
not grown same season as the ones in Figures 2 and 3).

Bruner (17) studied root development of the peanut at different
stages of development when the plants were grown in a sandy loam soil
in Oklahoma. When the soil was removed carefully with little disturbance
of roots it was observed that the tap root of mature plants had a length
of about 3 feet and that 4 or more rows of lateral roots grew horizontally’
for several inches and then downward for a distance of 2 or more feet.
In general, branch roots were perpendicular to the main roots. Numerous
temporary roots, designated as absorbing rootlets, were present on all
roots of the permanent system. Such rootlets either deteriorated with
age or developed into permanent roots. All young branch roots were
considered absorptive rootlets. During early stages of plant growth the
absorbing rootlets developed prominently in the first foot of soil, but
later the subsoil became progressively more and more filled with them.

In India (58) a similar experiment was conducted using Burmese, a
runner type, and Small Japan and Small Spanish, bunch types, with
results shown in table 3. These data indicate that the extensive root
system of the peanut might penetrate the soil to a depth of 6 feet.

96 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 3.—Root DEVELOPMENT (PENETRATION IN SOIL AND SPREAD) IN CENTIMETERS

Variety Age in | Penetra- | Spread Age in | Penetra- | Spread
days tion days tion
Small Japan...... 18 66 31 140 130 105
Small Spanish.... 18 60 41 140 150 80
Burmese......... 18 42 47 140 190 113
Small Japan...... 110 136 132
Small Spanish. ... 110 150 87
Burmese......... 110 192 112

It would be difficult to arrive at the relative weights of roots and
plant shoots since, because of their fragile nature, many roots are lost
when removed from the soil. Mohammad et al. (58), reported the green
weight of roots of plants 18 days old to be 75.4, 84.5 and 49.5 percent of
the green-shoot weight for Small Japan, Small Spanish and Burmese
varieties, respectively. At 140 days these values were 3.8, 2.6 and 3.3
percent, respectively. The proportion of roots to shoots gradually de-
creased with increasing age. Complete recovery of all roots to depths of
5 and 6 feet, as these workers attempted, would be difficult, which prob-
ably accounts for the low values obtained for older plants. Bledsoe and
Harris (10) found that when peanuts were grown in sand culture for
130 days, the average green weight of the roots of plants was 13.4 percent
of the green weight of the tops. The collective information indicates that
the root system of the peanut is much more extensive than is generally
realized.

Adventitious roots sometimes develop on lateral branches of runner-
type peanuts when in contact with the soil during humid conditions (37,
_ 58). This has been given little attention but it is probable that such roots
occur only on the more recumbent types under favorable moisture and
weather conditions. However, at times, these roots might be effective in
absorbing nutrients, and, if so, would increase the area of the absorptive
system of the peanut.

Root Hairs

The majority of papers reviewed state that few if any root hairs occur
on the root of the peanut plant. Pettit (63) failed to find root hairs while
Waldron (88) found hairs in limited numbers as rosettes at the base of
lateral branches and at tips of vigorously growing roots of young plants.
Plants in larger containers with less air drainage did not produce tip
hairs. Reed (68) observed few rosettes of hairs and no root-tip hairs on
field-grown plants. Mohammad et al. (58), found root hairs on peanuts

PHYSIOLOGY AND MINERAL NUTRITION 97

grown in containers, but not when grown under field conditions. Failure
to find hairs on the latter was thought to result from washing them off in
the excavation process. It has been reported (3) that the epidermis of
the roots of peanuts in the seedling stage sloughs off and typical root
hairs are not produced, although peculiar tufts of hairs form at the base
of most of the branch roots. Conversely, Bruner (17) indicated that root
hairs were plentiful on the absorbing rootlets of the field plants he
studied. Since the roots of peanuts are fragile, it is possible that the root
hairs in many cases may have been lost in the harvesting process. If,
however, peanuts have very few root hairs, as many believe, the major
portion of root absorption would be through channels other than root
hairs.

In summary, the plant has an extensive root system, the branches
sometimes have adventitious roots, the gynophores produce root-hair-like
outgrowths, and the fruit develops in the soil and sometimes has forma-
tions similar to root hairs on the shell. Nutrients could be absorbed by
each of these organs.

WATER AND OXYGEN RELATION

The peanut is classified as a mesophytic plant but has xerophytic
tendencies since it grows well in areas of Texas (68) and other States
which may be considered as a transition zone between the mesophytic east
and the xerophytic western plains.

Peanuts are usually grown on well-drained soils which are frequently
sandy in nature. This ecological relationship suggests that liberal amounts
of oxygen might be beneficial and that excessive moisture is not desirable
for best development of peanuts. Shibuya (74) indicated that oxygen in
the pegging area is necessary for fruit production, but the amount re-
quired was not determined. However, data relative to drought resistance,
water and oxygen requirements of the peanut plant are not available so
far as the writers are aware.

It is usually assumed that water enters plants largely through the
root hairs. If peanuts have few root hairs, then water absorption would
have to be by other means. As stated previously, adventitious roots,
root-like hairs on pegs and sometimes on shells of fruit, may be present,
but the relationship of those structures to water absorption has not been
established. However, it has been shown that pegs and developing fruit
do absorb some mineral elements (9, 19, 84). It is assumed that water
movement through the peanut plant would be similar to that of most
other plants.

98 THE PEANUT—THE UNPREDICTABLE LEGUME

LIGHT AND TEMPERATURE RELATIONS

Peanuts do not appear to be especially sensitive to length of day.
The plant seems to grow very well from the tropics to the middle tem-
perate zone. The day length in most of that area could be classified as
intermediate, which suggests that such is satisfactory for peanut growth.
In the United States peanuts are usually planted in April or May and
maximum fruit development probably occurs during July and August
when the days have begun to shorten. There is little seasonal variation in
day length in southern India, and peanuts are sometimes planted in the
fall in which case maximum fruit development occurs in the spring when
days are lengthening.

Moore (59) found that Spanish peanuts bloomed abundantly when
illuminated continuously for several weeks. Cheliadinora (21, 22) found
that longer days increased the green weight and flower production, al-
though the latter was not consistent. However, the ratio of fertilized to
unfertilized flowers was higher with the short-day plants. Shaded plants,
especially those on the shorter photoperiods, had fewer undeveloped pods
and gynophores, which was attributed to earlier flowering when a more
favorable lime and nutrient supply was available to aid development of
fruit which had set. These results indicate the length of day has an effect
on the peanut ; however, critical studies of the photoperiodic response are
lacking.

Although the intensity of light would seem to be important, few data
have been published in reference to its connection with peanuts. Moore
(59) found that when shaded plants were grown with 3- or 4-hour
periods of daylight, blooming was practically prevented because of in-
duced carbohydrate starvation, while Cheliadinora (21) produced good
yields under partial shade. Those results indicate that slight shading is
not particularly harmful as is a pronounced shortage of light.

Peanuts grown in an air-conditioned greenhouse at California Insti-
tute of Technology? required a high day temperature for normal develop-
ment. Cool ternperatures resulted in chlorosis and poor development.
Similar results have been observed at the Florida Station. These obser-
vations seem to be in agreement with the results of Cheliadinora (22)
that the photoperiodic treatment is effective only when the temperature is
favorable during the flowering period. An increase in temperature also in-
cteased the yield of fruit (22), which agrees with the general assump-
tion that the peanut is a warm-weather crop.

2 Personal correspondence, W. P. Jacobs. Princeton University.

PHYSIOLOGY AND MINERAL NUTRITION 99

PHOTOSYNTHESIS. CARBOHYDRATE
AND NITROGEN METABOLISM

It is assumed that photosynthesis and the carbohydrate and nitrogen
metabolism of the peanut are similar to that of other plants and a general
discussion of these topics may be omitted. However, it seems desirable to
mention the work of Moore (59) regarding the carbohydrate-nitrogen
balance in the metabolism of the peanut because of its possible importance
in relation to yields of field-grown plants. Moore produced plants with
various carbon/nitrogen ratios by altering the light and nitrogen supply.
High-nitrogen plants were succulent, dark blue-green in color, with
slender stems. High-carbohydrate plants were firm in texture, light in
color, with thick stems. Both types were weakly vegetative and non-
fruitful. Plants with a carbon/nitrogen ratio intermediate of the extremes
gave satisfactory yields. However, it was pointed out that the fruiting
tendency of the peanut was less sensitive to a change in the carbon/nitro-
gen ratio than that of the tomato plant. Results given in other papers
(10, 18, 37) suggest that the carbon/nitrogen ratio as affected by nu-
trient supply has considerable influence on flower and fruit production. It
is possible that many of the conflicting results in peanut experimenta-
tion would be explainable if such interrelations were better understood.

GROWTH-PROMOTING SUBSTANCES

Hormones or growth-promoting substances have not been used ex-
tensively on peanuts. Shibuya (73) reported that B-indole acetic acid in
lanolin, (proportion of 1 to 10), hastened germination when applied to
the scratched testa of seed of freshly harvested peanuts. He also reported
(75) that the number of flowers per plant was increased when sprouted
seed were soaked % and 2 hours, and unsprouted seed soaked 24 hours
in a water solution of 0.02 percent of that compound. A lanolin prepara-
tion of the hormone applied to sprouted seed hastened flowering and in-
creased the number of flowers.

Naphthalene acetic acid and five commercial hormone preparations
were used with field-grown Spanish peanuts at the Alabama Station (1).
The former and possibly one or two of the latter compounds slightly
increased nut production. However, there seemed to be little advantage in
their use and in some cases nodulation was depressed. Best results oc-
curred when the compounds were used in association with seed
inoculation.

100 THE PEANUT—THE UNPREDICTABLE LEGUME

Liu and Lou? were unsuccessful in stimulating the ovule into seed
development by means of a variety of substances, including auxins, vita-
mins and different plant extracts. Long immersion of the gynophore in
0.02 percent naphthalene acetic acid caused roots to develop just above
the undeveloped ovary. These workers were able to initiate fruit develop-
ment by grafting gynophore tips to detached cotyledons and culturing
them until the food supply of the cotyledons was exhausted.

Jacobs‘ indicates that the auxin which diffuses out of excised tips of
gynophores exhibits polarity of transport, that is, moves only from ovary
end toward the proximal end of the gynophore.

DORMANCY AND GERMINATION

Hull and Stokes (44, 81) reported dormancy of the peanut seed to
be hereditary in nature and that the rest period of some seed might be
as long as 2 years. The rest period of seed of the Spanish and Valencia
types ranges from 9 to 50 days, while that of some runner types might
range from 110 to 210 days. Seed of the Spanish types will germinate
in the field unless harvested promptly after maturation. The longer
rest requirement of the runner type is desirable if peanuts are left in
the field to be “hogged off” during the fall or winter months. However,
difficulties in germination of the runner peanut are rarely encountered
since the rest requirement is satisfied in the interval between fall harvest-
ing and spring planting. Hull (44) reported that the time required for
breaking the rest period of Florida Runner and Spanish seed was in-
creased when stored at 3° C. and decreased when stored at 20° to 40° C.
A regular practice was followed of storing seed at 30° C. for 30 days after
harvest, when quick germination was desired. The data indicate that the
rest requirement of the peanut seed decreased as storage temperature
increased from 3° to 40° C. which is opposite of that required by seed of
many crops.

Results by Beattie et al. (7) indicate that winter storage tempera-
tures of 32°, 40° and 70° F. had no significant effect on germination of
several varieties of seed tested. Unshelled, stored seed seemed to germin-
ate somewhat better than those shelled. Additional experiments to de-
termine the effect of age on germination were conducted with Valencia
and Improved Spanish varieties. When held at a storage temperature of
approximately 70° F. there was favorable germination of Valencia pea-
nuts for 5 years and of Spanish for 3 years, after which there was a dis-

3 Personal correspondence, Dr. P. S. Tang, dean, College of Agriculture, National Tsing Hua
University, Peiping, China.
4 Personal correspondence, W. P. Jacobs.

PHYSIOLOGY AND MINERAL NUTRITION 101

tinct loss in germination. Pons et al. (65) stored peanuts at minus 18° C.,
1° C. and 27° C. for 4 years. Those stored at 27° C. were not viable,
while those stored at lower temperatures germinated perfectly. In view of
these results it appears that the viability of peanut seed may be good for
from 3 to 5 years, depending upon the variety and the temperature of
storage.

The viability of seed is usually determined by a germination test. Re-
cently Brewer (16) reported good agreement between the tetrazolium
chloride chemical test and germinability by an ordinary method. If a
chemical method for determining the viability of peanut seed could be
perfected, it might be of considerable advantage to persons involved
in germination studies.

ABSORPTION OF MINERAL ELEMENTS

Mineral elements considered essential for plant growth, with minor
exceptions, are absorbed by the roots from the soil. It is generally assumed
that plant roots absorb ions either from the soil solution or by a root-
colloid exchange.

Cations such as calcium, magnesium, potassium, sodium and hydro-
gen are sorbed by the soil colloids. Through the phenomenon of base ex-
change the cations are liberated to the soil solution and thus become
available for intake by the roots. For example, carbon dioxide resulting
from root respiration or from the decomposition of organic matter can
react with the soil water to form carbonic acid. The hydrogen ions from
the carbonic acid may displace cations attached to the soil colloids. The
cations released to the soil solution as the result of ionic exchange can
then be absorbed by the plant. The base exchange reaction is reversible
and the amount of cations present in the soil solution at any time will
depend on several factors. Jenny and Overstreet (46) contend that by a
root-colloid exchange mechanism there can be a direct exchange of
ions between the root and the soil colloid. According to this theory, ions
sorbed on colloids may be as readily available to plants as ions free in
solution.

The plant absorbs anions from the soil solution. Anions, with the
possible exception of the phosphate ion, are not retained in any appreci-
able quantities in well-drained soils and unless used by crops are usually
leached out of the soil rather rapidly. The water-soluble phosphate com-
pounds are thought to be precipitated in the soil as insoluble or relatively
insoluble compounds which largely prevent their leaching. The supply
of soil phosphorus available to the plant depends on a series of complex

102 THE PEANUT—THE UNPREDICTABLE LEGUME

reactions which are not entirely understood. Two other important ele-
ments, nitrogen and sulfur, often occur in the soil in the form of organic
matter and are released to the soil solution as a result of decomposition.

The above discussion is only an indication of some of the factors in-
volved in supplying nutrients to the absorbing areas of plant roots. The
concentration of anions and cations of the soil solution is usually in-
creased by the addition of fertilizers, cover crops, lime and farm ma-
nures, as well as by nitrogen fixation by organisms and the removal of
sulfur and nitrogen from the atmosphere by rain water.

The absorption and accumulation of ions by plant roots is a compli-
cated process involving internal factors such as transpiration, respiration,
photosynthesis and other metabolic activities associated with growth.
Aeration, moisture, temperature and other environmental conditions sur-
rounding the roots are also known to influence absorption.

The absorption of ions by roots of the peanut plant is assumed to be no
different from that by other plants. However, since the fruit of the peanut
develops in the soil, its relation to ion absorption has been given con-
siderable attention. Several investigators (63, 68, 74, 88) suggested the
possibility of water and nutrient intake by the gynophore. Van der Volk
(85) observed that a soil extract aided fruit development, while Burk-
hart and Collins (19) were the first to demonstrate that an element, lith-
ium, was absorbed by the gynophore and distributed within the plant.
The latter workers also reported fruit quality to be benefited by the pres-
ence of calcium in the fruiting medium. Brady etal. (13, 15) demon-
strated that fruit filling was significantly increased when a single calcium
salt was added to the fruiting medium, while Harris (37) found fruit de-
velopment to be negligible when a calcium-deficient nutrient solution was
applied to that medium. It was reported (37) that yields were increased
when the sulfate ion was used in the fruiting medium, while Brady et al.
(15) failed to get a favorable response from that ion. It has been shown
also that nitrogen*®* (84), phosphorus", and radioactive cobalt (37)
are absorbed in small quantities by the developing fruit and translocated
to other parts of the plant. Bledsoe et al. (9) found calcium*™* to be
actively absorbed by the shells and seed of developing fruit with some
movement to other parts of the plant when the labeled calcium was ap-

ied to the fruiting medium. Conversely, when calcium** was applied
toithe roots of the plant, a small quantity of the labeled calcium was
found in the shell, but never more than a trace could be detected in the
seed of developing fruit.

*Small number refers to atomic weight.

PHYSIOLOGY AND MINERAL NUTRITION 103

FUNCTION OF NUTRIENTS AND DEFICIENCY
SYMPTOMS

The nutrients as a group are thought to have a number of general
roles, but in most cases it is difficult to state the exact function of a given
element. A deficiency of any essential element adversely affects plant
growth and yields. Mineral-deficiency symptoms are rarely found with the
peanut when grown under field conditions but have been observed with
plants grown in nutrient solution. Burkhart and Collins (19) described.
deficiency symptoms of the Virginia Bunch peanut in the young stage,
while other workers (10, 37) have described the effects of a deficiency
of the major elements for the Dixie Runner peanut at a later stage of
growth. However, the symptoms described are, at best, roughly qualita-
tive and in many instances are not specific. The role of nutrients in
peanuts is assumed to be similar to that of other plants and is discussed
briefly in connection with observed nutrient-deficiency symptoms.

Nitrogen. This element is the main constituent of protoplasm and
occurs in a number of other organic compounds, one of the most im-
portant being chlorophyll. One of the main functions of nitrogen is
obviously its requirement for the formation of new protoplasm in growth.
Large amounts of nitrogen usually cause peanut plants to become dark
green in color, grow rapidly, producing succulent vegetation that does
not flower and fruit well (58). A lack of nitrogen in the peanut plant re-
sults in stunted growth, yellow foliage, reddish coloration of stems, and
few nodules are found on the roots (19). .

Phosphorus. Young meristematic tissue contains considerable phos-
phorus where it is utilized in the growing region in the formation of
nucleoproteins and a number of other phosphorus compounds, including
important respiratory enzymes and intermediates. Without phosphorus
nuclear division and meristematic activity is decreased. Considerable
quantities are stored in fruit and seed, hence the yield and size of seed
may be affected. This element hastens maturity and root development.
Peanuts with a low phosphorus content have a small leaf surface. The
leaves are a dull bluish green in color, and in later stages they become
yellowish and drop.

Potassium. Potassium occurs largely in the plant as soluble organic
and inorganic salts. It is transported from the older parts to the actively
growing regions of the plant under conditions of potassium deficiency.
The exact function of potassium is obscure, but it is thought to play a part
in the formation and translocation of various carbohydrates, the utili-

104 THE PEANUT—THE UNPREDICTABLE LEGUME

zation of nitrogen, and in cell division. Potassium-deficient peanut plants
(10, 37) have few necrotic “scorch” areas at the leaf margins. In the late
stages of potasium deficiency the stems near the tips of branches become
reddish in color, then brown, which is followed by death of the tissue.

Calcium. Most of the calcium of plants occurs in the foliage and very
little is found in the seed. The peanut seed is especially low in this ele-
ment. Calcium-oxalate crystals are sometimes found in plant tissue.
Calcium is considered relatively immobile in plants. Root growth of the
peanut is severely affected by a shortage of calcium. A deficiency causes
stunting and small distorted leaves near the tips of the branches. Inter-
veinal brown pitted areas which coalesce to form larger necrotic spots
develop on the affected leaves which give the leaves a bronze color. Basal
stem cracks and die-back of the affected shoots occur during later stages.
A deficiency of calcium (27) also affects the fill and quality of peanut
fruit.

Magnesium. The chlorophyll molecule contains magnesium, and since
a deficiency of this element results in chlorosis, it plays a part in photo-
synthesis. Although only a small proportion of the magnesium of the
leaf can be accounted for by that in the chlorophyll, a large proportion of
this element is carried in the green foliage, and there is a considerable
amount in the seed. Magnesium leaf deficiency symptoms of the peanut
(19) appear first as a chlorosis of margins of older leaves. In later stages
the leaf margins may become orange in color. Magnesium has been
demonstrated to be a factor in fruit production (10, 77, 78).

Sulfur. Sulfur is well distributed in the plant in the form of proteins,
volatile compounds, and sulphates. Sulfur is not a part of the chlorophyll
molecule. However, it may be required in the process of chlorophyll
formation, since deficient plants have a pale green color. It seems to af-
fect root development and to have an important part in respiration pro-
cesses and cell division. The writers grew peanuts on a minus sulfur
nutrient solution and the plants were smaller, but no other visible de-
ficiency symptoms appeared. Burkhart and Collins (19) indicate that a
deficiency of sulfur caused the leaves to be a lighter green color.

Iron. Plants grown on soils of high pH values frequently show
iron-deficiency symptoms because of its unavailability. Iron is not a part
of the chlorophyll molecule, and yet a deficiency results in chlorosis. It is
assumed to have a catalytic effect in oxidation-reduction processes within
cells, and it is found in enzymes. The quantity of iron present in plants is
very small and it is quite immobile. Typical iron chlorosis developed
when peanuts were grown in Hoagland’s and Arnon’s nutrient solution

PHYSIOLOGY AND MINERAL NUTRITION 105

FERTILIZER
ALL MINORS
Om COPPE

Figure 5.—Dixie Runner peanuts showing the effect of 10 pounds per acre of copper
chloride applied to Arredonda loamy fine sand before seeding. Right, complete
fertilizer, including microelements ; left, complete fertilizer, only copper omitted.

ryt

” a ae pes
Courtesy Florida Agricultural Experiment Station
Figure 6.—Foliage of G. F. A. Spanish peanuts grown on soil treated before seeding

with a complete fertilizer and all microelements, except copper. Note the extreme
copper deficiency symptoms. The few yellowish-white spots are associated with
the deficiency, but the relationship of the dark leaf spots has not been in-
vestigated.

106 THE PEANUT—THE UNPREDICTABLE LEGUME

(42) by the drip-culture method (76). The deficiency was corrected
quickly by spraying iron on the plants.

Boron. A deficiency of boron affects the growing tissues, similar to
that of calcium, resulting in death or growth abnormalities. The mobility
of calcium is related to the boron supply. A boron deficiency for peanuts
(19) resembles a calcium deficiency re that the necrotic areas are
localized near the leaf margins.

Manganese. Manganese is in some way related to chlorophyll produc-
tion since a deficiency results in a chlorosis of plants. It seems to play a
part in oxidation and reduction processes possibly through its effect on
enzymes. Shear and Batten (71) reported that when peanuts were grown
on heavily limed soils the foliage was chlorotic and yields were reduced
due to the unavailability of the manganese.

Copper and Zinc. A deficiency of copper results in chlorosis, prevents
nitrogen from functioning normally (32, 35), and reduces yields. Harris
reported that in copper deficiency the bud area of the peanut was affected,
the terminal leaflets were chlorotic, small and distorted, a few yellowish-
white spots appeared on many leaves, and the yields were greatly reduced
(figures 5,6). The pattern was much the same as that reported by Allison
et al. (2) when peanuts were grown on soils in the Everglades and was
similar to that attributed to thrip injury by Shear and Miller (72) and
to leafhopper injury by Metcalf (53). It is quite possible that such char-
acteristics are similar to those resulting from insect injury. However, the
symptoms described above did not occur when copper was applied to the
soil before peanuts were planted.

Zinc-deficiency symptoms of the peanut have not been described,
although some workers (2, 6) have reported that applications of zinc
have increased yields.

Molybdenum. Molybdenum is considered an essential element for
some plants (82, 86). The foliage of the peanut plant had a dark green
color when a small amount of molybdenum was applied to the soil, and
shoot growth was increased by its addition to nutrient solutions (37).

CHEMICAL COMPOSITION

The data of mineral analyses of various parts of peanut plants as
compiled from several sources (26, 33, 43, 48, 83) are given in tables
4 and 5. Few values for sulfur were found, and it would appear that the
evaluation of this element would merit more attention. The results given
in these tables merely indicate the mineral content of plants when grown
under various conditions. Therefore, caution should be used in drawing

107

PHYSIOLOGY AND MINERAL NUTRITION

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108 THE PEANUT—THE UNPREDICTABLE LEGUME

conclusions about the differences in mineral composition, because there
are practically no comparative analyses of different types of plants when
grown under controlled or known conditions.

Seed

The mineral composition of mature seed of peanuts is relatively con-
stant for a given variety. The nitrogen (protein) content of seed of the
Spanish type is reported (79) to be higher than that of the Virginia pea-
nut. However, while the data (5, 30, 33, 43, 91) of nitrogen content as
well as that of other elements indicate varietal differences, it is not known
whether such differences are significant. Data of mineral composition of
seed as compiled from several sources (26, 33, 43, 48, 83) are given in
tables 4 and 5.

Table 5.—RANGE IN. PERCENTAGE OF INORGANIC CONSTITUENTS IN THE PEANUT
KERNEL, AFTER HOFFPAUIR ET AL. (33, 43)

Potassium.............. .68-. 89 ZinGiseavivesss ieee ate .0017—.08
Calcium... cee eee .02—.08 Manganese............ .0008-.05
Magnesium............. .09-, 34 DEO a. accuacdidunestsig wessielt aca .0018-.10
Phosphorus............. .25-.66 COpper naktivet ie gets .0007-.03
Sulfur sy sega ears ediciones .19-,24 Boron sigs cvaaveaees oes .0026-.05
Molybdenum.......... .0008-.003

Hoffpauir and Guthrie (43) report that 87 percent of the nitrogen
of the peanut seed is present as arachin and conarachin. Their data indi-
cate that the amino acids usually considered essential for animal growth
are present in the seed.

The average percent oil content of seed of control treatments from
results of Middleton et al. (54) are as follows: 48.5, 49.1, 50.1 and 51.8
for Virginia Bunch, North Carolina Bunch, Spanish 2B, and White
Spanish, respectively. Others (30, 43, 91) have reported results indicat-
ing some varietal differences in oil content. Several workers (30, 54, 62,
74) have shown that the oil content of mature seed is much higher than
that of shrivels and immature seed. Those data suggest that an accurate
description of seed samples should be included when oil analyses are
reported.

The composition of oil from Spanish seed (33, 43) is given in table 6.

Peanut oil is nondrying, edible, and has a specific gravity of 0.917-
0.920, refractive index of 1.467-1.470, saponification number of 186-
194, and iodine number of 85-100 (33, 43, 93).

There is little change in the free fatty acid content or iodine number

PHYSIOLOGY AND MINERAL NUTRITION 109

Table 6.—OIL FROM SPANISH PEANUTS

Glycerides Percent
Oleic ie sone cde Gath tein 52.9
Linolei@ecs s snsgee x aee ster 24.7
Palmitiy siie.sise's cap ce te 8.2
SECARIC acs oid aoadss Gematol 6.2
Arachidic............... 4.0
Lignoceric.............. 3.1
Unsaponifiable material... 0.2
Totals 2i.0c2osnwaee oak oer 99.3

of the oil of unshelled peanuts when stored in closed cans at 1° C. for 2
years (80). Oil of seed stored at 27° C. for 4 years (65) is much less
stable than that of seed stored at 1° C. or at minus 18° C. for the same
period. The oil of immature seed (62) has a higher free fatty acid content
than that of mature seed.

Peanut seed is an excellent source of the B vitamins (33, 40, 43, 64)
but contains only small quantities of the A, C and D vitamins. The ap-
proximate range in values of vitamin content as microgram of vitamin per
gram of seed is as follows: riboflavin 1.05-1.57, thiamin 8.5-14, nicotinic
acid 88-200, niacin 144-158, pantothenic acid 25, pyridoxin 3, biotin 0.34,
inositol 1800, and folic acid 2.8. A considerable quantity of vitamin E is
also present. Heat above about 150° C. decreases the vitamin content (29,
40). Fertilization of the soil is reported to have had no effect on the B,
content of peanuts (67) but there were large varietal differences.

Values of some of the organic constitutents of the peanut seed as
compiled from the results of Fraps (30) are given in table 7. Similar
values have been published by others (40, 43). Results by Burkhart
(18), Jodidi (47) and Moore (59) show that the organic composition
of peanut seed can be influenced by environmental factors which affect the
growing plant, but the data are too limited for generalization. The litera-
ture offers little information on the organic composition of the seed dur-

Table 7.—RANGE IN PERCENTAGE OF CARBOHYDRATES AND OTHER COMPONENTS OF
THE PEANUT KERNEL

7.42 | 35.25 | 54.15 | 4.26 | 21.20) 3.05 | 0.28; 5.21; 3.18] 2.72
4.00 | 24.10 | 40.85 | 2.06} 6.02 | 1:82 | 0.06) 2.31] 0.94] 2.20

110 THE PEANUT—THE UNPREDICTABLE LEGUME

ing its development. As stated previously, mature seed have a higher oil
content than immature seed. Very immature seed are quite high in free
fatty acids (62) which decrease to a low level at maturity. Gallup and
Staten (31) report an increase of protein and oil and a decrease of crude
fiber and nitrogen-free extract of seed with shells during the last 5-week
period of development.

Analysis (43) of the skin or testa of seed shows it to be high in fiber
and ash and to contain appreciable amounts of fat and nitrogenous ma-
terials.

Shells

The mineral composition of shells is given in table 4. The mineral
content of seed is little affected by fertilization, whereas that of the shell
(28, 51, 52) has been used as an index of the calcium supply available to
the developing fruit. Indications are that at least four factors affect the
mineral composition of shells, namely (a) development of seed, (b)
nature of the soil colloids, (c) calcium and other nutrients supplied the
peanut, and (d) the length of time the fruit remains in the soil. Empty or
poorly filled shells (28) have a higher nitrogen, potassium and magnesium
content than the shells with well-developed seed, while the calcium con-
tent of the shell is not consistently affected by seed development. The
peanut fruit seems to be able to obtain more calcium (51, 52) from some
types of soil colloids than from others with the same degree of calcium
saturation. Moreover, the application of calcium to the soil where peanuts
are grown increases the calcium content of the hulls (28). Results by
Bledsoe and Harris (10) indicate that the shell of the fruit absorbs very
small amounts of magnesium and phosphorus from the medium in which
it develops but actively absorbs calcium (9) and possibly potassium. The
writers have observed also that the potassium content of shells of peanuts
which cling to the vines when harvested is much higher than that of shells
of peanuts removed ftom the soil after harvest.

The approximate organic composition of peanut hulls as compiled
from the results of Fraps (30) is given in table 8. Little work has been

Table 8.— APPROXIMATE COMPOSITION OF PEANUT HULLs,
(percentage—dry basis)

Pfotein..........000005. 7.31 Reducing Sugars....... 0.59

Ether extract........... 1.19 Disaccharide sugars..... 1.72
Crude fiber............. 65.73 StARCH ut cosie ne jelkawes 0.74
N-free extract........... 21.22 Pentosans............. 17.82

ASN i itieje gcd vne ware aceon 4.53

PHYSIOLOGY AND MINERAL NUTRITION 111

done on factors which influence the organic content of shells. However,
Moore (59) reported that shells of peanuts grown on a high nitrogen
solution had a slightly higher ether extract and nitrogen content than
those grown on a very low nitrogen solution.

Gynophores

A deficiency of any of the macro-elements (10) gives a low content
of the particular element in the young gynophores. Furthermore, a de-
ficiency of calcium or magnesium seems to cause the potassium content
to be higher, and conversely. Apparently the level of nitrogen (59) in
the nutrient solution influences the amount of the various carbohydrates
in this organ.

Roots

The data of Killinger et al. (48) do not indicate any consistent strik-
ing differences in the mineral composition of the roots of plants which had
received various fertilizer and sulfur-dusting treatments. However, there
seemed to be a gradual decrease in content of some elements of roots when
harvested at different dates after planting (table 4). The results of Moore
(59) indicate that a high nitrogen content in the nutrient solution de-
creases the starch, sugars and other carbohydrates of the roots.

Foliage

The mineral composition of the foliage of peanuts is quite variable
as shown in table 4. Some of the variation is probably due to variety dif-
ferences, but few comparisons have been made of, varieties grown under
the same conditions. Values of peanut hay reported by Collins and Morris
(26) differ from the values for the more mature hay given in this table.

Data of table 4 indicate that the mineral composition of the foliage is
affected by maturity. This is further substantiated by the results of
Burkhart and Page (20) who sampled leaf blades 2, 3 and 5 months after
planting and found that the average concentration of calcium, magnesium,
phosphate and sulfate increased with maturity, while the potassium con-
tent decreased from the first to second sampling, but increased from the
second to the third sampling. Other results (20, 61) show that different
parts of the foliage vary in mineral composition. Calcium seemed to be
highest in the middle and lower leaves, potassium and phosphate in
young tissue, magnesium in the more mature tissue, and sulfates in the
lower portions of the plant, especially the lower petioles and stems.

Results by Bledsoe and Harris (10) indicate that the nutrient supply

112 THE PEANUT—THE UNPREDICTABLE LEGUME

to the roots has a pronounced effect on the mineral composition of the
foliage. A deficiency of any major nutrient element to the root zone re-
sulted in low values of that element in the leaves. A deficiency of potas-
sium gave high calcium and magnesium values of the leaves, and a de-
ficiency of either calcium or magnesium seemed to increase the potash
content of the leaves. Other workers (19, 70) have secured similar
results. Data of foliage analyses frequently show wide variation which
is to be expected since it is known that both climatic and soil conditions
influence the mineral content of plant leaves.

Some data of organic constituents of peanut hay are given in table 9.

Table 9.—AVERAGE PERCENTAGE COMPOSITION OF MowED PEANUT Hay, CoMPILED
FROM RESULTS OF FRaps (30)

Protein.............008- 11.09 | Nitrogen-free extract.... 42.11
Ether extract........... 5.09 Sie tesa aca sie ctagtetan 9.77
Crude fiber............. 21.94 Water iune xis toe sawew fs 10.00

According to Moore (59) when peanut plants were grown on a
range of nitrogen levels from very high to very low, the foliage con-
sistently increased in total sugars, starch and dextrians, while the per-
centage of soluble solids and total nitrogen decreased as the nitrogen
supply to the roots decreased. Hemicelluloses did not seem to be related
to the nitrogen level on which the plants were grown. He suggested that
total nitrogen rather than any specific nitrogen fraction should be used
in correlating nutritional studies of the peanut.

FOLIAR DIAGNOSIS

Diagnostic methods involving analytical or plant-tissue tests have re-
ceived considerable attention in recent years. In general, analyses of the
entire plant are not recommended since specific tissues are considered
to be more reliable as an indication of the mineral condition of the plant.
Leaves are frequently chosen because their nutrient content more nearly
reflects the supply from the soil. Standardization of tissue tests for known
conditions may be useful especially when values of elements below the
limits regarded as necessary for plant growth are the ones of interest
from the viewpoint of fertilization.

Analyses of the peanut seed are of little diagnostic value since its
mineral composition is relatively constant. The mineral content of the
shell is influenced by nutrient supply but analyses of that organ would
serve only as a fertilizer guide for the coming year. It would appear that

PHYSIOLOGY AND MINERAL NUTRITION 113

analyses of leaves or stems might be best for diagnostic purposes,
especially if corrective measures are to be practiced.

Studies of tissue tests with the peanut are limited, but they seem to
merit more attention, especially evaluations for known or controlled con-
ditions. Burkhart and Page (20, 61) found variations in mineral content
of different parts of the foliage of the peanut and state that the following
tissues were most indicative for specific tests: Calcium, lower blades;
magnesium, lower petioles; potassium, top petioles; phosphorus, top
blades; sulfur, lower stems. The lower leaf blades of the peanuts were
thought to be the most suitable tissue for determining deficiencies or
excesses of all mineral nutrients in the plant. Chemical tests of the lower
blades gave results which correlated with response to fertilization of
field-grown plants.

SHEDDING OF FRUIT

Since the peanut blooms during a period of 2 to 3 months, there are
various stages of fruit development as the plant approaches maturity.
Many crops of indeterminate growth habit are harvested two or three
times during a season. This is impossible with the peanut plant, since it is
removed from the soil in the process. If peanuts are harvested early, there
will be a large number of immature fruit, and if late, the most mature
fruit will be left in the soil by the harvesting process (11, 39, 57, 66).
The amount of shedding or fruit loss is undoubtedly related to a number
of factors such as the degree of ripeness, amount of disease, insect dam-
age, and various cultural treatments. Different seed inoculations (1) have
necessitated harvesting at different times, also applications of gypsum
(19) have- resulted in early defoliation, making early harvest necessary.
Shedding was decreased by sulfur dusting (11, 39) and was also in-
fluenced by fertilizer and other treatments (39). The number of fruit
shed may be very few, but occasionally, when harvested late or under
unusual conditions, as much as 75 percent (39) of all peanuts produced
may be left in the soil after harvesting. Therefore, it is quite important
in evaluating experimental results to know whether the technique used
in harvesting accounts for all the peanuts produced.

NUTRITIONAL BALANCE

A lack of balance in nutrient supply (34, 49, 87) frequently: accentu-
ates nutritional disturbances. Published results (10, 19, 37) show that a
deficiency of any element to the peanut will quickly produce abnormal
plants which deteriorate rapidly. These deficiencies markedly affect the

114 THE PEANUT—THE UNPREDICTABLE LEGUME

vegetative character, flower and fruit production, and the mineral compo-
sition of the plants. This balance relates not only to the nutrient supply
in the root area, but also in the fruiting area. Plants are vegetative and
produce few fruit when calcium is not applied to the fruiting area (10,
37). Thus, the nature of the entire plant may be altered by the lack of
calcium in the fruit zone. This does not mean that fruit absorption of
nutrients is as important as root absorption, but the special requirements
of the fruiting organs cannot be disregarded in the evaluation of fertilizer
requirements.

A number of workers (14, 15, 19, 20, 70) have emphasized the effect
of the calcium-potassium relationship on fruit production. Others (83)
have indicated that the potassium-magnesium ratio is important in this
respect and that the relation of the calcium, potassium and magnesium
supply was indicative of the relative yield of marketable nuts. The im-
portance of a balanced ration for plants is obvious. However, it is impos-
sible to strive for a balanced nutrient program for the peanut until factors
responsible for yields are identified.

NUTRITION AS RELATED TO DISEASE

The relation of the nutritional status of the peanut plant to its disease
susceptibility is probably more important than generally realized. The
prevalence of leaf-spot infection was far greater on plants grown on a
magnesium-deficient solution than of plants grown on a deficiency of
other elements (12). Applications of gypsum have also been reported (19)
to cause the foliage of peanut to be very susceptible to leaf spot, resulting
in early defoliation.

Concealed damage of the peanut seed is any internal breakdown of the
cotyledons which is not evident upon external examination. Wilson (92)
indicates that one type of concealed damage appears to be physiological
in nature, but its occurrence was unimportant in Alabama. Internal
breakdown of the seed might be related to nutrition but experimental
evidence of such is lacking.

Sulfur dust is commonly applied to the foliage of peanuts to control
leaf spot and certain insects. The sulfur may also act as a nutrient in
some instances, especially where the supply of sulfur in the soil is low
(8, 38). Some results’ suggest that when sulfur was applied to the soil
the foliage of the peanut plant was less susceptible to the leaf-spot in-
fection.

5 Unpublished results, Florida Agricultural Experiment Station.

PHYSIOLOGY AND MINERAL NUTRITION 115
DISCUSSION

Physiological processes relative to vegetative growth and fruit pro-
duction of the peanut plant are assumed to be similar to those of many
other plants. If differences exist, they are perhaps quantitative rather
than qualitative. A balance of many physiological factors is necessary for
the production of a healthy plant with a vigorous vegetative growth, many
flowers, and adequate organic and inorganic reserves to support heavy
fruiting. Whether the physical condition of the soil has an influence on
penetration by the gynophore and subsequent development of the fruit is
unknown. It has been shown that some mineral elements are absorbed
by the fruiting organs and the data indicate that small amounts of available
calcium in the fruiting zone aid fruit development. However, most of the
mineral intake of the plant is by the root system.

In most well-drained soils the penetration of roots is limited not by
soil conditions but by factors inherent within the plant. The data suggest
that the peanut plant has an extensive root system and the roots are more
or less continuously growing through the soil and are constantly coming
in contact with soil particles from which cations can be displaced and
absorbed. There are no data comparing the mineral uptake by the peanut
plant with that of other plants from the same medium. However, it ap-
pears that the root system of the peanut is very effective in extracting
nutrients from sandy soils of low nutrient supply. Whether that effective-
ness is related to the nature of absorbing roots or to the extensiveness of
the root system of the plant or the combination of both factors is un-
known.

Physiological processes related to the nutrient supply in general
determine the yield of field grown peanuts. The peanut is rather sensi-
tive to an unbalanced nutrient supply and undoubtedly the application of
one or two elements to the soil in some instances has produced an un-
favorable nutrient balance which may account for some of the conflicting
results of fertilizer field trials (11, 26, 39, 89). The only pronounced yield
responses reported with peanuts have been on restricted areas where the
available soil supply of calcium (27, 54, 69, 70), magnesium (70, 77, 78),
or microelements (2, 6, 36, 71) has been very low. All these facts indicate
the need for additional data in order to deal more effectively with the
complex problems of soil and plant interrelations arising in the field.

SELECTED REFERENCES
(1) Avsrecat, H.R.
1944, FACTORS INFLUENCING THE EFFECT OF INOCULATION OF PEANUTS GROWN
ON NEW PEANUT LANDS. Soil Sci. Soc. Amer. Proc., 8:217-220.

116
(2)

(3)

THE PEANUT—THE UNPREDICTABLE LEGUME

ALLIson, R. V., Bryan, O. C. anD HuntER, J. H.
1927, THE STIMULATION OF PLANT RESPONSE ON THE RAW PEAT SOILS OF THE
FLORIDA EVERGLADES THROUGH THE USE OF COPPER SULFATE AND
OTHER CHEMICALS. Fla. Agr. Exp. Sta. Bul. 190.
ANON,
1947. EARLY LIFE OF PEANUTS STUDIED. N. C. Agr. Exp. Sta., 70th Ann. Rpt.,
21-23.

4) ———

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

(16)

1946, pEANuTs. N. C. Agr. Exp. Sta., 69th Ann. Rpt., 37-47.
BalLey, W. K., Pickett, T. A. AND FuTRAL, J. G.
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PHYSIOLOGY AND MINERAL NUTRITION 117

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CHAPTER V

SOIL PROPERTIES, FERTILIZA
TION AND MAINTENANCE
OF SOIL FERTILITY

E. T. YORK, JR. AND W. E. COLWELL’

Properties of Soils on Which Peanuts Are Grown

GENERAL SOIL PROPERTIES

A soil well adapted to the production of peanuts has often been char-
acterized as a well-drained, light-colored, loose, friable, sandy loam, well
supplied with calcium and with a moderate amount of organic matter.
While such a soil may be considered to be “ideal,” peanuts may be grown
on soils differing markedly in physical and chemical characteristics.

A number of factors other than the yielding capacity of a soil deter-
mines its suitability for the production of this crop,/ Peanuts are normally
grown on light sandy soils not necessarily because these soils produce the
highest yields; in fact, there are many indications that better yields
may be obtained on some of the heavier-textured soils. The principal
reason for growing peanuts on the lighter soils lies in the fact that the
crop is more easily harvested and the soil does not adhere to the pods,
Many of the heavier-textured clays and clay loams are more deeply
colored and tend to stain the pods to such an extent as to lower the
market value of the crop. These factors are of little consequence when
the crop is harvested by grazing hogs; however, it would not be a de-

1E. T. York is associate professor of agronomy, North Carolina Agricultural Experiment
Station, and W. E. Colwell is head, Department of Agronomy, North Carolina State College of
ee are indebted to J. F. Reed for his suggestions regarding the arrangement of sub-

ject matter to be presented in this chapter and to W. L. Nelson for his constructive criticisms in
the preparation of the manuscript.

SOIL FERTILITY 123

sirable practice to harvest nuts by hogs on many of the heavier soils be-
cause of the likelihood of damage to the physical structure of the soil.

Extremely heavy, sticky clays which tend to cake or crust are not
well suited to peanut production because of the difficulty of peg pene-
tration at fruiting time.

Under favorable conditions it is difficult at times to secure good
stands of peanuts, and in wet, poorly drained soils satisfactory stands are
virtually an impossibility. Peanuts have a distinct taproot and, as with
other deep-rooted plants, it is essential that they be grown on a well-
aereated soil with good drainage.

Variations in the chemical properties of peanut soils are limited some-
what by the exacting demands for proper physical characteristics. Soils
of desirable color, texture and drainage usually have a relatively low ex-
change capacity . . . in most cases between one and five milliequivalents
per 100 grams of soil. These soils are generally low in organic matter
and reserves of plant nutrients. While peanuts may appear to make fair
yields on land too poor for most other crops, it should not be implied that
this crop is best adapted to relatively infertile soils. The fact that peanuts
are grown on soils of low native fertility merely emphasizes the need for
an extremely careful program of fertilization and management in order to
maintain a high level of production of peanuts and other crops grown
in the rotation.

PROPERTIES OF SOILS IN VARIOUS PEANUT
PRODUCING AREAS

(1) The United States: The majority of the peanuts produced in the
southeastern United States are grown on Coastal Plain soils. Batten
(29) considers the Norfolk fine sandy loam as the soil best suited to
growing the large-seeded type peanut ; and a large acreage of the peanut
crop grown in North Carolina and Virginia is produced on soils of the
Norfolk series. The Sassafras, Marlboro, Moyock and Craven are also
considered to be good peanut soils, while the poorly drained Bladen and
Portsmouth soils are not adapted to growing this crop (29).

Generally, the soils of the small-seeded Peanut Belt in Georgia,
Alabama and Florida are more sandy and have a lower exchange capacity
and organic-matter content than the peanut soils of the Virginia-Carolina
area. The Alabama Agricultural Experiment Station reports (4) that
high yields of peanuts have been obtained on all the major soil areas of
that State. However, most of the crop grown for market is produced on
the light, sandy, Coastal Plain soils of the southeastern part of the State.

124 THE PEANUT—THE UNPREDICTABLE LEGUME

Most of the well-drained soils in central and northern Florida are
satisfactory for growing peanuts, according to Killinger et al. (65) at
the Florida Experiment Station. These workers have observed that some
of the waste-pond phosphate fields and areas surrounding phosphate
mines and lime quarries are especially well adapted to the production of
high yields of peanuts. The Norfolk, Arredondo, Newberry, Orange-
burg, Ruston, Red Bay and Magnolia soil series are commonly used for
growing peanuts in Florida, while the “flatwood soils” are considered
poor for the production of this crop.

Parham (84) reports that most of the peanuts produced in Georgia
are grown on Coastal Plain soils in the southern part of the State. In
areas where the peanuts are produced for market, the crop is grown on
some of the relatively heavy soils such as the Greenville, Magnolia and
Orangeburg. Lighter soils such as the Norfolk, Tifton and Ruston are
used primarily in areas where the peanuts are hogged off, according to
Parham.

Downing, Aull, Goodman and Peterson (48) have classified the soils
of South Carolina into four groups based on their suitability for growing
peanuts. A description of these groups follows:

“Group A: Excellent soil types for peanuts. Generally well drained
with sandy loam or similar textured surface layers and with friable sandy
clay loam on sandy clay subsoils beginning 10 to 24 inches below the
surface. The soil as a whole is at least 36 to 48 inches deep and may be
more. The topography is favorable for tillage operations and erosion is
not a major problem.

“Group B: Good soil types for peanuts. Soils in this group, though
generally similar to those in Group A, differ in characteristics such as
thickness or texture of the surface layer, internal drainage, gravelliness
or stoniness, or slope. The surface layer of a good soil may have either a
lighter or heavier texture and may be shallower or deeper than that of
an excellent soil.

“Group C: Fair soil types for peanuts. Soils in this group usually
have one or more unfavorable characteristics such as a fine textured,
very coarse textured, or very deep open or sandy upper layer, a notice-
able eroded condition, steep slope, or imperfect drainage.

“Group D: Poor soil types for peanuts. Soils in this group are poor
for peanuts because of characteristics that limit production or prevent
proper cultivation of the land. Included are very sandy, very clayey,
hilly to mountainous, wet or swampy, and rocky soils. If these soils are
used for peanuts, yields will be very low.” These suitability groups might
well apply to soils of other peanut-producing regions.

SOIL FERTILITY 125

The peanuts produced in other States in the South and Southwest
(41, 67, 103) are grown on soils similar in physical and chemical charac-
teristics to those used in the major peanut-producing areas in the South-
east.

(2) Other parts of the World: Workers in Jamaica (24, 25), Hawaii
(66), Mexico (70), Cuba (109), Columbia (22), the Philippines (51),
Australia (63, 64, 90, 111), Senegal (26), South Africa (79, 92, 98),
Indonesia (23) and Rhodesia (108) have reported that the soils best
suited for peanut production in their respective countries were, in general,
those having the characteristics of the “ideal’’ peanut soil described
earlier in this chapter. Hence it is evident that there is universal agree-
ment on what constitutes the most desirable soil for growing peanuts.

THE FERTILIZATION OF PEANUTS

Peanut-fertilization practices have changed little in the United States
in the past several decades; significantly, perhaps, neither have the yields.
This is in sharp contrast to most of the other crops grown in the same
areas.

A review of the peanut fertility research conducted by the southeast-
ern experiment stations reveals a multitude of inconsistent and apparently
conflicting data. The anomalous behavior of the peanut is pointed out as
follows in a report of a recent study by the Southern Research Institute

(21):

“Not only does the peanut fail to respond markedly to direct ap-
plications of commercial fertilizers, but such responses as are observed
are not constant, varying widely from field to field even on the same
soil type. This behavior is in marked contrast to that of other crops
such as corn or cotton for which the yield increase to be obtained for a
given application of fertilizer can be predicted with almost mathe-
matical certainty.”

Despite this unusual behavior, peanuts are not unlike other crops in
their basic nutritional requirements. In fact, with the normal systems
of management in which both hay and nuts are harvested, peanuts re-
move relatively large amounts of nutrients from a soil (table 1). Cer-
tainly there is little reason to suspect that the chemical and physical laws
which govern the absorption and utilization of nutrients by peanuts are
not the same as for other plants. What accounts, therefore, for the erratic
behavior of the peanut in response to fertilizer amendments?

Until recently little attention has been given to the fact that peanut
varieties exhibit marked differences in nutrient requirements. Yet, while

126 THE PEANUT—THE UNPREDICTABLE LEGUME

striking differences among varieties in their response to fertilization may
be reconciled, the anomalous, inconsistent results often obtained in ferti-
lizer experiments with a single variety have been more difficult to under-
stand. As pointed out in Chapter III, peanuts are normally self-pol-
linated, and the-plants within a given newly selected strain or variety are
essentially homogeneous. Therefore, genetic variability should be at a
minimum and observed differences within such a variety must necessarily
be a result of environmental influences. Failure to evaluate fully the
various environmental factors influencing the growth of peanuts has
made it difficult to interpret much of the experimental data.

Table 1.—NuTRIENTS REMOVED FROM THE SOIL BY ONE ToN OF PEANUTS AND Two
Tons or Hay (PouNDS PER ACRE). COLLINS AND Morris (43). ;

Part of Yield per
the Plant Acre N P05 KO CaO MgO
Pounds Pounds Pounds Pounds Pounds Pounds
Hay 4,000 78.80 10.60 82.20 55.00 25.20
Kernels 1,280 56.30 12.90 10.90 1.10 4.00
Hulls 720 4.60 0.80 9.90 2.83 1.10

Total pounds of indi-
vidual nutrients

removed 139.70 24.30 103.00 58.90 30.30
Percent of total nutri-
ents in hay......... 56.40 43.60 79.80 93.40 83.20

As pointed out previously, peanuts are often grown on soils of low
native fertility. In many cases these soils are already deficient or on the
threshhold of being deficient in a number of essential elements. It is
common knowledge that under conditions where two or more nutrient
elements are limiting growth, little benefit is derived from one nutrient
unless all of the deficient elements are supplied simultaneously. The fact
that peanuts often fail to respond to certain fertilizers may be due in part
to a state of multiple nutrient deficiency.

It is difficult to evaluate much of the peanut fertility data in the litera-
ture because of the lack of information concerning the soil on which the
work was conducted. A rather complete characterization of the physical
and chemical properties of the soil would undoubtedly facilitate a better
understanding of the experimental work with peanuts. Furthermore, an
interpretation of peanut-fertilization data must also take into account
the previous cropping and fertilization history of the soil.

Failure to appreciate fully the unique growth and fruiting habits of
the peanut has certainly led to some of the confusion regarding the ferti-

SOIL FERTILITY 127

lization of this crop. Since nutrients may be absorbed by the developing
pegs as well as by the roots (34, 40, 110), the problem of fertilizer
placement becomes of greater importance with peanuts than with many
other crops. Recent experiments (20, 38, 45) indicate that to obtain the
most beneficial effect of some nutrients, they must be supplied to the
zone of fruit formation rather than to the plant roots. On the other hand,
there are indications that it is best to supply certain other nutrients to
the rooting medium (20, 37, 40). Another problem associated with ferti-
lizer placement results from the fact that stand injury may occur when
_ certain fertilizer materials are placed too close to the seed at planting
(20, 31). Obviously the effectiveness of fertilizer materials may, to a
large extent, depend upon proper placement, and such materials may
lower yields unless they are used correctly.

The yield of peanuts may be influenced greatly by the stage of ma-
turity of the plant at harvesting. If the crop is harvested early, a large
proportion of the nuts is immature. Yet, if harvesting is delayed too long,
an excessive number of the nuts may be separated from the vines and
remain in the soil. There is evidence in the literature that certain fertility
treatments may hasten or delay the maturity of the plants (30, 89).
Certainly, plants must be harvested at comparable stages of maturity if
the effects of fertilizer amendments are to be measured accurately.

Recent work has indicated that fertilizer treatments may influence
the number of nuts which are shed and remain in the soil at harvest (35,
58). Therefore, this differential effect of fertilizers upon shedding may
influence the yield of peanuts as normally measured. Perhaps the effect of
certain fertilizer materials upon shedding is related directly to their in-
fluence upon maturity.

It should be evident from the foregoing discussion that peanut ferti-
lization practices are not as well defined as with many other crops, and
many of the anomalies associated with peanut fertilization are yet to be
explained. Without question, experimental work with peanuts presents
problems and requires techniques which are quite specific to this crop.
However, when due consideration is given to the peculiar fruiting habits
of the peanut plant as well as to the many important, but often unrecog-
nized, environmental factors which influence its behavior, the available
information pertaining to the fertilization of peanuts begins to assume a
much more orderly pattern.

No attempt will be made in this discussion to review all of the experi-
mental work with peanut fertility. Such a review would undoubtedly tend
to confuse rather than clarify the issue because of the difficulty in eval-

128 THE PEANUT—THE UNPREDICTABLE LEGUME

uating much of the data in the literature due to the lack of information
regarding the conditions of the experiments. Instead, certain data will be
presented which tend to illustrate specific principles regarding the fertili-
zation of peanuts and the maintenance of the fertility of peanut soils.
From these data, it should be possible to formulate some fairly definite
ideas regarding the use of fertilizer materials with peanuts.

EXPERIMENTS WITH NITROGEN, PHOSPHORUS
AND POTASSIUM

Nitrogen

Being a leguminous plant, peanuts might not be expected to respond
to large applications of nitrogen, and some of the experimental data would
tend to verify this supposition. However, there is also considerable evi-
dence which would indicate that nitrogen is of value in peanut fertilizers.

Recently, Prevot (91) has emphasized the importance of nitrogen in
the nutrition of peanuts. The data presented by this French worker indi-
cate that relatively large quantities of nitrogen are translocated from the
leaves to the developing fruit, suggesting the importance of maintaining
the peanut plant at a high level of nitrogen metabolism prior to the fruit-
ing period. However, no evidence is presented by Prevot to indicate that
amendments of nitrogen would be necessary when the peanut plant was
properly inoculated with nitrogen-fixing microorganisms.

Responses to nitrogen might be expected if peanuts have not been well
inoculated. While it has been generally assumed that no inoculation is
necessary if peanuts are grown on land used previously for this crop, little
has been done to determine if the most satisfactory inoculum is commonly
present in peanut soils. Symbiotic nitrogen fixation may be inhibited
somewhat in acid soils (69); hence response to nitrogenous fertilizers
might be more pronounced on such soils. Unfortunately, most nitrogen-
fertilization data in the literature are not accompanied with information
relative to soil pH and to the degree of inoculation of the peanuts grown
in the experiments.

It has been suggested (30) that nitrogen may be beneficial on soils
which are extremely low in organic matter. Certainly differences in ni-
trogen levels in soils would be expected to be reflected in the response
of peanuts to additions of nitrogenous fertilizers.

Workers at the Georgia Experiment Station (9) have found that
nitrogen applied to Spanish peanuts caused a marked reduction in the
disease, Southern root rot (Sclerotium rolfsii), and it was observed that

SOIL FERTILITY 129

the yields of peanuts closely followed the incidence of the disease. These
data would suggest that in some cases the beneficial effect of nitrogen
may be due to its secondary influence in reducing the severity of this
disease.

The results of experiments conducted over a 10-year period at the
Georgia Coastal Plain Experiment Station (13) show a small, progres-
sive increase in peanut yields with each increment of nitrogen up to 32
pounds. The maximum response, however, was only 151 pounds of nuts.
In another single-element experiment there was little effect on yields of
withholding nitrogen from a complete fertilizer (12).

As the result of several years of experimentation, workers at the
North Carolina Station (43, 47) have concluded that nitrogen fertilizers
have little effect upon the yields of large-seeded peanuts.

Several experiments conducted in Mississippi and reported by West
(112) show little beneficial effect of 16 or 32 pounds of nitrogen in a
complete fertilizer. In some cases the addition of nitrogen tended to re-
sult in a lower yield of nuts. The results of other work reported by West
show responses of 200 to 300 pounds of nuts from the application of 100
pounds of nitrate of soda as a side dressing.

"McClelland (68) in Arkansas, has reported that the addition of 18
pounds of nitrogen to a White Spanish variety resulted in an increased
yield of 1,188 pounds of nuts and 1.38 tons of hay.

Earlier work at the Alabama Experiment Station (49) indicated that
nitrogen was of little value in peanut fertilizers. However, more recent
experiments (1, 107) have revealed some marked responses from the ad-
dition of nitrogen to Spanish peanuts. The data in table 2, obtained by
the Alabama workers, show that in 1943 the yield of nuts was more than
doubled by the addition of 120 pounds of nitrogen as nitrate of soda to a

Table 2—TuHE RESPONSE OF SPANISH PEANUTS TO ADDITIONS OF NITROGEN ON A
Norrotk SAnpy Loam. REPORTED By ALABAMA AGRICULTURAL EXPERIMENT
STATION. (1) :

Pounds per Acre

Treatment 1943 1944 Average

Nuts Hay Nuts Hay Nuts Hay

No nitrogen....... MC Gan annie 787 | 2,279 | 1,508 | 4,503 | 1,148 | 3,391
120 pounds nitrogen
(750 pounds nitrate of soda)....} 1,909 | 3,395 | 2,298 | 6,008 | 2,104 | 4,702

*All plots received 1,000 pounds of superphosphate and 250 pounds of muriate of potash per acre.

130 THE PEANUT—THE UNPREDICTABLE LEGUME

Norfolk sandy loam. The 2-year averages show an increase in yield of
956 pounds of nuts due to the applied nitrogen. Furthermore, large in-
creases in hay yields resulted from the added nitrogen. These data are
sharply in contrast with those obtained in earlier experiments with
smaller rates of nitrogen.

The results of experiments conducted at two other locations in Ala-
bama in 1944 are shown in table 3. The yields of Spanish peanuts were
increased with each successive increment of nitrogen up to 80 pounds.
The seed yield of runner peanuts was not increased by applications of
nitrogen greater than 20 pounds per acre. However, the vegetative growth
of both runner and Spanish type peanuts was stimulated by the added
nitrogen. The Alabama workers (107) report that the high levels of

Table 3—Tue INFLUENCE OF AMENDMENTS OF NITROGEN UPON THE YIELDS OF
SPANISH AND RUNNER PEANUTS ON A NorFOLK SANDY LoaM. REPORTED BY ALABAMA
AGRICULTURAL EXPERIMENT STATION. (1)

Treatment Yield of runner® | Yield of Spanish
Peanuts Peanuts

Pounds per Acre | Pounds per Acre

INGHE ys. siieceds wee a uly a de Nala Gene e pihas 1,429 1,044
20 pounds nitrogen®.................... 1,617 1,202
40 pounds nitrogen..................... 1,605 1,352
80 pounds nitrogen...................-. 1,544 1,626
120 pounds nitrogen.................0.-. 1,635 1,686

® Peanuts were inoculated.
b All plots received 1,000 pounds superphosphate and 250 pounds muriate of potash per acre,
° Nitrogen applied as nitrate of soda.

nitrogen did not affect the percentage of sound or mature kernel, rotten
kernels, or pops of either Spanish or runner type.

In view of some of these data which show highly profitable responses
from the application of nitrogen to peanuts, it might be well to re-examine
some of the earlier work with this element. In most of these experiments
less than 32 pounds of nitrogen were used, and in many cases recom-
mendations are based on studies in which only 6 to 8 pounds of N per
acre were applied. The recent work at the Alabama Station suggests
that these amounts of nitrogen are insufficient to realize a measurable in-
crease in peanut yields.

In 1922, Batten (30) in experiments with large-seeded peanuts re-
ported that large quantities of nitrogen used on fairly fertile soil generally
stimulated the top growth, delayed the maturity, and resulted in peantits
of poor quality without materially increasing the yields. Other investiga-

SOIL FERTILITY 131

tors (96) have indicated that nitrogen may stimulate vegetative growth;
however, the increased growth is often of little benefit because of the cor-
responding reduction in the shelling percentage of nuts. From our present
knowledge of peanut nutrition it appears possible that the poor quality of
nuts might have been due in many cases to a deficiency of calcium. Cer-
tainly the need for calcium and other nutrients would increase as the
vegetative growth was stimulated, and little beneficial effect from nitro-
gen could be expected if some other nutrient were limiting.

In view of the conflicting evidence in the literature, it is not possible
to reach a satisfactory conclusion relative to the use of nitrogenous
fertilizers with peanuts. However, there are sufficient data to suggest the
possibility of obtaining profitable responses from nitrogen when adequate
supplies of other nutrients are present. Surely this problem warrants
further investigation.

Phosphorus

There is considerable disagreement in the literature regarding the
value of phosphorus in peanut fertilizers. Harper (56) and Pate (85)
have indicated that phosphorus stimulates the setting of fruit and de-
creases the number of unfilled pods. Other workers (89, 108) have sug-
gested that phosphorus may hasten the maturity of peanuts. While there
is no question regarding the plant’s need for phosphorus, table 1 shows
that a relatively small amount of this element is absorbed by the peanut
plant and suggests that little may be gained from large applications of
phosphatic fertilizers except, perhaps, on soils extremely low in avail-
able phosphorus.

Some of the earlier work in the United States and in several foreign
countries indicates that a greater yield response might be obtained from
phosphorus than from either nitrogen or potash. Batten (30) in 1922 re-
ported that phosphorus gave better results than any other element in
peanut fertilizers and recommended the use of 300 to 500 pounds per
acre of superphosphate. On some of the Black Belt soils of Alabama,
peanuts were found to be more responsive to phosphorus than to any
other element (3). As the result of experiments conducted in Mississippi,
Ferris (52) in 1922 concluded that “acid phosphate” gave the cheapest
increase in the production of peanuts.

Kerle (62), in New South Wales, indicated that superphosphate had
proven to be the most beneficial fertilizer for peanuts in that country.
Moses and Sellschop (79), in South Africa, reported profitable increases
in peanut yields from the use of 300 pounds of superphosphate. Krauss

132 THE PEANUT—THE UNPREDICTABLE LEGUME

(66) has indicated that applications of 250 to 500 pounds of phosphate
to peanuts in Hawaii have been very beneficial.

In a recent experiment conducted by Massibot and Vidal (71) in
Senegal, phosphate at the rate of 132 kilograms per hectare (approxi-
mately 125 pounds per acre) was found to increase markedly the yields of
peanut hay and nuts. The large responses to phosphorus were obtained on
a soil which had been fallow for 2 years. These workers also observed
that peanut yields were increased as the result of the residual effect of
phosphatic fertilizers applied the previous year to millet.

Numerous field experiments with peanuts conducted by the North
Carolina Agricultural Experiment Station (46, 47) have failed to show
any marked beneficial effect of phosphatic fertilizers when peanuts were
grown in rotation with other crops which had received liberal applica-
tions of phosphatic fertilizers. However, when peanuts were grown con-
tinuously on the same soil, yields were increased by additions of phosphate
on soils low in available phosphorus (16).

The results of a 10-year study at the Georgia Coastal Plain Experi-
ment Station (13) in which peanuts were grown after crops which had
been “fairly well” fertilized showed no effect of additions of 48 pounds
of P,O, on peanut yields. In experiments conducted at several locations
by the Georgia Experiment Station (6) on soils which had been “well
fertilized in past years,” little response was observed from applications
of phosphorus.

The behavior of peanuts toward amendments of phosphatic fertilizers
appears to be dependent upon a number of factors. If the crop is grown
on “new” land or land which has been fallow for a number of years, or in
a rotation with other nonfertilized crops, phosphatic fertilizers would un-
doubtedly be beneficial in many instances. However, when grown in ro-
tation with other well-fertilized crops, peanuts might be expected to give
little response to phosphorus amendments.

In view of the rather exacting demands of some varieties of peanuts
for calcium, some of the increases in yields which have been attributed to
phosphorus may have been due to the calcium supplied in the phosphatic
fertilizers. Evidence of this is found in the work of Albrecht (27) which
shows that the addition of superphosphate to Spanish peanuts favorably
influenced yields while triple superphosphate was of no value. O’Brien
(82) has also found that superphosphate and dicalcium phosphate were
superior to triple superphosphate as a source of phosphorus for peanuts.
Ordinary superphosphate is approximately 50 percent by weight of cal-
cium sulfate.

SOIL FERTILITY 133

Potassium

It is well recognized that peanuts are especially heavy ‘‘feeders” of
potassium. Yet, despite the relatively large amount of potassium absorbed
by peanuts (see table 1) the yield responses to applications of potash
fertilizers are often very small or negligible, even on soils of low K con-
tent. In fact, peanuts appear to be quite unique in their ability to absorb
potassium and make satisfactory growth on soils so deficient in available
potassium that many other crops would fail to grow.

An average of the yields obtained in an experiment conducted at the
Georgia Coastal Plain Experiment Station (13) over a 10-year period
shows that the use of 32 pounds of potash in combination with nitrogen
and phosphorus increased the yield of Spanish peanuts only 139 pounds
per acre. In experiments conducted by the North Carolina Station (46)
between 1938 and 1943, 12 to 48 pounds of K,O per acre proved bene-
ficial in only one of the locations. In several instances the yields were
actually reduced by the application of potash. The exchangeable potassium
level of these soils was 75 pounds or greater at each location.

CORRECTED YIELD| TRUE SHELLING
IN| POUNDS PER CENT
PER ACRE

O=NO TREATMENT
K=48 LBS. K,0

O K
(e)

Re]

-—| to

fap) a
L ttn Z
NO WITH NO WITH
CALCIUM CALCIUM CALCIUM CALCIUM

Courtesy N. orth Carolina Agricultural Experiment Station (47)

Figure 1.—The response of peanuts to potash, with g and without addi-
tions of calcium. Soil = Kalmia sandy loam; pH = 5.3; exchange
capacity = 3.13 m.e./100 grams; exchangeable Ca, Mg, and K =
0.50, 0.27 and 0.12 m.e./100 grams respectively. Calcium equiva-
lent to 130 pounds CaO was auld as CaSO4.2HeO on the
foliage in July.

134 THE PEANUT—THE UNPREDICTABLE LEGUME

Other experiments conducted in North Carolina (18, 37, 47) in
1942, 1943 and 1944 revealed some interesting relations regarding the
response of peanuts to potash. It was found that on a soil low in both
potassium and calcium there was a significant increase in yield from
the addition of potash when adequate calcium was supplied. Without the
addition of calcium, potash was found to decrease the yields of peanuts,
‘however. This relation is illustrated in figure 1. Apparently the deleteri-
ous effect of potash in the absence of applied calcium was due to the re-
duction in shelling percentage (figure 1). As shown in figure 2, the re-
sponse of peanuts to potash was found to be dependent upon the initial
level of potassium in the soil. On soils at a medium potassium level, ferti-
lizers containing this element were of little value. It was observed that
the vegetative growth was stimulated by the added potash and that the
increased yields were due to the effect of the potash on the plant size and
number of fruit rather than on kernel development. Other workers (40,
76, 96) have also observed that potash may stimulate vegetative growth

CORRECTED YIELD TRUE SHELLING

IN| POUNDS PER CENT
PER ACRE
O = NO TREATMENT Oo
K = 48 LBS K20 a
K ie
Oo « 4 K te
vs ©
0 i ie
@
6
nm
(an)
mee)
é iN
SOIL LOW SOIL MEDIUM SOIL LOW SOIL MEDIUM
IN POTASH IN POTASH IN POTASH IN| POTASH

CALCIUM REQUIREMENTS MET ON BOTH SOILS
Courtesy North Carolina Agricultural Experiment Station (47)

Figure 2—The response of peanuts to potash amendments on soils containing
different amounts of exchangeable potash. Soil low in potash was a Norfolk
sand with 0.04 m.e. exchangeable K; soil medium in potash was a Norfolk
sandy loam containing 0.10 m.e. exchangeable K per 100 grams.

SOIL FERTILITY 135

but cause a reduction in peanut quality. However, under the conditions
reported in figure 1, this harmful effect of potash on peanut quality was
overcome by maintaining an adequate level of calcium in the soil.

Other studies in Georgia (6, 7, 8, 13), Florida (5, 65, 105), Alabama
(1, 49), Mississippi (14), South Carolina (83) and elsewhere (67) have
given no consistent results with potash fertilizers, and it would be im-
possible to’: make a recommendation regarding the use of potash which
would be applicable under all conditions. Generally the consensus among
the southeastern experiment stations is that it is preferable to apply rela-
tively large amounts of potash to the other crops grown in the rotation
rather than to supply this material directly to peanuts. However, on soils
extremely low in potassium or where heavily fertilized crops are not in-
cluded in the rotation, it may be desirable to apply some potash directly
to the peanuts.

There is evidence that potash applied to peanuts may be harmful if
the material is not used properly. Experiments in North Carolina (20)
have shown that stands of peanuts were significantly reduced when
either muriate of potash or potassium metaphosphate was placed directly
underneath the seed. Furthermore, when potash was applied on top of the
row (in the pegging zone) as late as June 15, yields were decreased and
a large number of undeveloped-kernels or “pops”’ resulted. The practice of
applying potash to the top of the row as the plants come through the
ground has been found to be satisfactory in some localities (20). Investi-
gators in Virginia (31) have observed no reduction in peanut stands
when potash fertilizers were placed in bands at least 2 inches to the side
of the seed and below the seed level. Thus side placement at planting or
top dressing at emergence would appear to be the best method of applying
potash fertilizers directly to peanuts.

EXPERIMENTS WITH CALCIC MATERIALS

The calcium requirements of the peanut plant have long been recog-
nized. Jones (61) in 1885, describing a soil suitable for the growing of
peanuts, said, “Unless (the soil) contains a goodly percentage of lime in
some form in an available state, no land will produce a paying crop of
pods, although it may yield large luxuriant vines.” In a subsequent dis-
cussion, Jones pointed out that a soil must contain adequate calcium in
order to insure “solid pods.” Thus, the need for and function of calcium in
the production of peanuts was recognized some 65 years ago and perhaps
earlier.

136 THE PEANUT—THE UNPREDICTABLE LEGUME

THE IMPORTANCE OF CALCIUM IN PEANUT NUTRITION

The significance of calcium in the nutrition of peanuts is clearly de-
picted in figure 3. The data in this graph were obtained in experiments
conducted by the staff at the North Carolina Agricultural Experiment
Station (47) on soils ranging in calcium levels from approximately 450
pounds to 2,200 pounds of calcium-carbonate equivalent per acre. Very
marked increases in yields were obtained from additions of gypsum, a
soluble calcium salt, to soils low in calcium. Yet it is evident that little
might be gained from amendments of gypsum to soils already well sup-
plied with calcium. Furthermore, it is obvious that increases in yields ob-
tained from the gypsum on low calcium soils were due for a large part
to the effect of the calcium on the shelling percentage.

CORRECTED YIELD IN TRUE SHELLING
POUNDS PER ACRE PER CENT
B
B eel A=NO TREATMENT A gf
fo) BO 6) B = GYPSUM a my
A IR Oy Is
—) te ol Is o} fc
= o ¢ B B
no = = 14.9
Nt
A
ive)
an
i}
ref
LSD B
(.05)
A
©
N
i #
LOW SOIL MEDIUM SOIL HIGH SOIL LOW SOIL MEDIUM SOIL HIGH SOIL
CALCIUM CALCIUM CALCIUM CALCIUM CALCIUM CALCIUM

Courtesy North Carolina Agricultural Experiment Station (47)

Figure 3.—The effect of gypsum upon the yields and shelling percentage of peanuts
growns on soils of different calcium levels.

Soil Low | Soil Medium| Soil High
Chemical Characteristics ‘in Calcium | in Calcium | in Calcium
Disses Shes Xow x eagle deny Joy Gaaw Ease Bee Swale 6.0 5.5 5.6
Exchange Capacity—m.e./100 gms............... 000005 2.66 3.24 4.02
Exchangeable Ca—m.e./100 gms............0 000000 e eee 0.45 1.39 2.21
Exchangeable K—m.e./100 gms.............6 0.00.0 0005 0:05 0.08 0.10
Exchangeable Mg—m.e./100 gms.....................0. 0.18 0.29 0.38

SOIL FERTILITY 137

Many other investigators (80, 109) have indicated that the quality of
peanuts is influenced by calcium to a greater extent than is the quantity
of fruit. A deficiency of calcium in soils is usually manifested by a large
number of “pops” or unfilled pods. The better quality of nuts in soils well
supplied with calcium is evidenced by a whiter, firmer hull, well-de-
veloped kernels and an increase in weight per bushel of unshelled nuts.
Colwell and Brady (44) have observed that in addition to decreasing the
number of pops, calcium also functions in increasing the number of two-
cavity fruit formed by the large seeded varieties. They suggested that
calcium exerts this favorable effect by preventing abortion of the ferti-
lized ovules which apparently occurs at a very early stage of fruit de-
velopment before shell enlargement has begun. Brady, Nelson and Reed
(15) have further indicated that calcium may increase the percentage of
pegs which make shells.

As early as 1911 Duggar and Funchess (50) reported highly profit-
able increases in peanué yields from the use of lime in Alabama. In recent
tests on Alabama soils which were relatively low in calcium and which
had been subjected to intensive cultivation, Rogers (95) obtained very
marked responses from the use of lime. Increasing the calcium level of
the soil from approximately 400 pounds per acre of CaCO,, equivalent to
800 or 900 pounds by the application of lime, resulted in a five-fold in-
crease in yield of Spanish peanuts. Rogers reported that on soils low in
calcium, additions of lime up to 3,000 pounds gave marked increases in
yield of both Spanish and runner-type peanuts.

The results of a 10-year experiment conducted on a Tifton sandy loam
by the Georgia Coastal Plain Experiment Station (13) showed that lime
applied at the rate of 500 and 1,000 pounds per acre was of little value
for peanuts. It was reported that the test “followed a general rotation in
which other crops were. fairly well fertilized.”” However, there is no indi-
cation of the calcium level of the unlimed soil.

In field experiments conducted in Uganda, East Africa, peanuts have
shown no response in yields to amendments of lime (60). Workers in
Senegal have reported a 35-percent increase in peanut yields from appli-
cations of 3 tons of lime per acre (60).

In a test of some 13 different varieties and strains of peanuts by
McClelland (68), in Arkansas, increases of as much as 2,000 pounds of
nuts and 3 tons of hay per acre were obtained with certain varieties from
the application of 1,056 pounds of crushed limestone. The average in-
crease in yield from lime with all the varieties was 890 pounds of nuts
and 1.03 tons of hay.

138 THE PEANUT—THE UNPREDICTABLE LEGUME

Numerous tests conducted in Virginia have emphasized the need for
calcium in the production of large-seeded varieties of peanuts. Batten
(29) has suggested that an adequate calcium level may be maintained by
applying 1,500 to 1,800 pounds of ground limestone per acre or its equiva-
lent to peanut soils every 3 or 4 years. Large applications at one time
have been found to be harmful. It was suggested that the pH be main-
tained between 5.8 and 6.2, and on the lighter soils the pH should never
exceed 6.4. Batten reports that gypsum is almost universally used where
the large-seeded peanuts are grown. However, this material has not been
found to increase yields where lime has been used to maintain a “suit-
able” soil reaction.

The results of other experiments at different localities in the United
States are varied. The response or lack of response may be explained
in most cases by the mineralogical nature of the soil and the level of
calcium. Generally, however, the soils on which peanuts are grown are
relatively low in calcium and unless large amownts of lime have been
applied in recent years some benefit may be expected from the use of this
element.

SouRcES OF CALCIUM

There is considerable evidence that peanuts will make satisfactory
growth on relatively acid soils provided the calcium needs of the plant
are satisfied. Thus, the primary consideration in the use of lime or other
calcium-bearing materials for peanuts is to furnish an adequate supply
of the nutrient calcium. The three calcium-bearing materials most com-
monly used for peanuts are gypsum or landplaster (CaSO,.2H,O), cal-
citic limestone and dolomitic limestone. Numerous tests have been made
to determine the most satisfactory of these materials for peanuts.

Little differences in peanut yields were observed at two locations in
Mississippi (14) from the use of 400 pounds of gypsum under the seed,
400 pounds of gypsum dusted on the plants, and 400 pounds of dolomite.
However, little response was obtained from any of these treatments. In
other experiments 1,200 pounds of lime yielded somewhat better than
400 pounds of gypsum.

Comparable yields of large-seeded peanuts were obtained in experi-
ments in Virginia (30) with 500 pounds of gypsum, 2,000 pounds of
burnt shells, and 4,000 pounds of ground shells. Other studies (32) in-
dicated that ground oyster shells and dolomitic limestone were of equal
value for peanuts.

Rogers (95) studied the effect of ten sources of calcium upon the yield

SOIL FERTILITY 139

of Spanish and runner peanuts grown in a rotation with vetch. The lime
materials were applied broadcast at two rates, 1,500 and 3,000 pounds
per acre, toa Norfolk sand. The results are shown in table 4. All of the
calcium sources were found to be approximately equal in value except the
calcium silicate slag which gave profitable increases over no lime but was
inferior to other liming materials. Dolomitic limestone was found to be

Table 4.—PEANUT YIELDS AS AFFECTED By KINDS AND RATES OF LIME AND GROWTH
OF VETCH AS A GREEN MANURE Crop, AUBURN, ALABAMA.* (95)

Lime treatment Vields of Yields of
Soil vetch Spanish
Pounds pH turned peanuts,
. per acre Sept. under, pounds per
Kind of lime applied, 1945 pounds acre
1941 per acre
1942-45 1943-45
NORGE. 6.00600: sale cad haan ooee wns —_ 533 5,766 1,093
Calcic limestone (Av. of 3 sources).| 1,500 5.3 14,720 2,073
3,000 5.5 16,701 2,307
Dolomitic limestone (Av. of 3
SOURCES) sks siete densa haan bSapes 1,500 5.3 16,073 2,165
3,000 5.6 18,615 2,633
Oyster shell.........0.....0000. 1,500 5.3 16,874 1,871
3,000 5.6 16,894 2,242
Paper mill waste................ 1,500 5.3 18,743 2,203
3,000 5.7 16,757 2,415
Blast furnace slag............... 1,500 5.2 13 ,243 1,666
3,000 5.6 15,694 2,198
T.V.A. Ca-silicate slag........... 1,500 5.4 14,822 1,978
3,000 5.6 15,341 1,732

+*Maximum response to lime obtained in these tests in small plots by turning under vetch each year
as a green manure crop, close spacing of plants, and fertilizing both vetch and peanut crop with 300
pounds per acre of 0-14-10. Peanuts were planted and dug each year from these plots on Norfolk loamy
sand since 1942. (The 1942 crop was lost after harvesting.)

superior to calcitic lime on an intensively cropped Norfolk sand but was
not significantly better in larger-scale field tests on sandy loam soils.
Experiments were conducted in North Carolina (47) to compare the
relative values of dolomitic and calcitic limestone and gypsum, applied at
different dates and in different manners. The results are shown in table
5. Calcitic limestone was found to be distinctly superior to dolomitic
limestone, regardless of the time of application. Furthermore, almost
twice as much dolomite had to be applied: to furnish the same amount of

140 THE PEANUT—THE UNPREDICTABLE LEGUME

calcium as was supplied by calcitic lime. Pure magnesium carbonate was
found to decrease the yields somewhat. At one location 640 pounds of
gypsum appeared to be superior to calcitic lime while at another the lime
resulted in higher yields.

It is obviously very difficult to evaluate the effectiveness of various
sources of calcium. In many instances arbitrary comparisons have been

Table 5.—Y1ELD OF VIRGINIA BUNCH PEANUTS AS AFFECTED BY DIFFERENT CALCIUM
AND MAGNESIUM CARRIERS. REPORTED BY NORTH CAROLINA AGRICULTURAL
EXPERIMENT StTaTION 1944, (47)

Treatment To Supply Vield—Pounds per acre
Method and time of application of Location
materials and rate in pounds per acre | Calcium |Magnesium I* Ty**

Pounds Pounds
CaO MgO
per Acre per Acre

No treatment............00ee eee —_— — 74 889
Broadcast February 15

Dolomitic limestone 1974....... 600 430 928 1515

Calcitic limestone 1074....... 600 — 1174 2008

Dolomitic limestone 1316....... 400 286 533 1541
In row at planting—April 25

Dolomitic limestone 658....... 200 — 415 843
On row at emergence—May 14

Landplaster 640....... 200 = 1644 1468

Burnt lime 200 5 soe nies 200 —_— 808 1289

Dolomitic limestone 658....... 200 143 570 1011

Calcitic limestone 358.4 boos } 200 — 907 1618

Magnesium carbonate 300....... —_ 143 47 694
On foliage—July 7

Landplaster 600....... 200 _ 1209 1907
L.S.D. LOS sctvacCenasieuaiersceeee _ —_ 233 244

ROU oe pencesnct bance ar eens _— ~_ 313 329

*Norfolk sand; pH = 5.0; exchangeable soil calcium = 0.38.
**Norfolk loamy sand; pH = 5.0; exchangeable soil calcium = 0.46.

made between two or more calcium-bearing substances with little effort
made to place the materials on a comparable basis . . . that is, to add
equivalent amounts of calcium or to use quantities of liming materials of
equal neutralizing power. Furthermore, many of the calcium materials
are carriers of other elements which may also influence the experimental

results. Despite these difficulties, from the existing knowledge of the use’

of liming materials and of the calcium needs of peanuts, it should be pos-

SOIL FERTILITY 141

sible to predict the most effective means of supplying calcium to this
crop.

On most soils it would appear to be better to meet the calcium needs
of peanuts by liming materials rather than through the use of neutral cal-
cium salts such as gypsum. With the possible exception of tobacco, most
of the crops which might be grown in rotation with peanuts would benefit
from the use of lime on the more acid soils. Furthermore, on very acid
soils (below pH 5.0) peanuts themselves may respond more to liming
materials than to additions of neutral calcium salts. For example, the

loll fi,
Courtesy North Carolina Agricultural Experiment Station (81)

Figure 4.—The response of Virginia Bunch peanuts to additions of one ton of
dolomitic limestone. The stunted, light colored plants, were growing on soil
at a pH of 4.7 and with 0.46 me. of exchangeable calcium.

response to lime may be evidenced by a darker, greener vegetation and an
increase in plant size as shown in figure 4. The stunted, light-colored
condition of peanuts on very acid soils is due in part to a deficiency of
nitrogen, resulting from a reduction in activity of nitrogen-fixing micro-
organisms. Mann (69) has reported that the addition of lime to virgin
Norfolk and Coxville soils (pH 5.3 and 4.5) resulted in a large increase
in nodulation of peanuts while gypsum reduced the nodulation. In view of
recent work (53, 77, 97, 113) with other legumes, the poor growth of
peanuts on very acid soil may be due in part to a toxicity of such elements
as manganese, iron and aluminum. Too, there is evidence (28, 39, 78)

142 THE PEANUT—THE UNPREDICTABLE LEGUME

that with certain plants calcium is not absorbed as readily in acid media
as in those of a higher pH.

Peanuts are especially heavy “feeders” of potassium and the plant may
absorb considerably more of this element than is needed. Certainly it
would be desirable to reduce this luxury consumption of potash if the
yields were not adversely affected. There is considerable evidence (86,
87, 93, 113) that the addition of lime to soils will result in a decreased
absorption of potash by the plant. On the other hand, gypsum may in-
crease the uptake of K (93, 113). The differential effect of the two ma-
terials upon potash absorption provides another point in favor of the use
of limestone rather than gypsum for peanuts.

On soils ofextremely low-exchange capacity, it may be necessary to
“apply a soluble source ‘of calcium in addition to lime in order to supply
adequate amounts of calcium.

Recent fundamental studies (37, 46) have emphasized the specific
need of the peanut for calcium and have shown that cations of a similar
nature, such as magnesium, cannot be effectively substituted for calcium.
If the primary objective in using lime for peanuts is to supply the nutrient
calcium, it should be desirable to use a material which would be most ef-
fective in meeting that need. When the soil pH is increased beyond a cer-
tain point by liming, certain minor-element deficiencies may be en-
countered. Thus there is an obvious limit to the amount of lime which
may be safely used. Yet dolomitic limestone is used almost exclusively in
some peanut-producing regions, and less than one-half the amount of cal-
cium is supplied by this material in liming a soil to a given pH as would
be added were calcitic limestone used. Therefore, from the standpoint of
meeting the calcium requirements of peanuts, it should be more desirable
to use a form of calcitic limestone rather than one high in magnesium.

Some soils used for the production of peanuts are low in magnesium,
and the superiority of dolomitic limestone observed in certain experi-
ments has undoubtedly been due to a magnesium response. However, the
magnesium requirement of peanuts is relatively low and, on soils deficient
in this element, it might be desirable to supply the needed magnesium in
the fertilizer or to use a mixture of calcitic and dolomitic limestone. If
such a mixture were used, it would appear to be desirable to keep the
ratio of Ca to Mg in the liming material relatively high.

PLACEMENT OF CALCIUM

~ Recent studies (40) have shown that much of the calcium absorbed
by the peanut roots is immobilized in the leaves and stems, and insuf-

ei ae

SOIL FERTILITY 143

ficient quantities are normally translocated to the developing gynophores
to insure well-developed kernels. The studies have further shown that
calcium may be absorbed directly by the developing pods and have
indicated that for proper kernel development it is very important that an
adequate supply of calcium be present in the zone in which the fruit are
formed.

By using a technique in which the runners on one side of the plant
could “peg-down” in one medium and the fruit on the other side of the
plant could develop in a different medium, Brady (36) was able to

Figure 5.—The influence of gypsum upon the formation of well developed pods. The
fruit on the left developed in a media supplied with a calcium sulfate solution,
while those on the right were supplied with distilled water only. Brady (36).

demonstrate quite clearly the importance of proper placement of calcium.
Figure 5 shows that an abundance of well-developed pods were formed on
the side of the plant which had received calcium while relatively few
healthy fruit were produced on the other side in a medium which had not
been supplied directly with calcium. This work clearly shows that calcium
is not readily translocated from one part of the plant to the other. Other
data (table 6) reported by Colwell and Brady (45) demonstrate the im-
portance of proper placement in the use of calcium-bearing materials for
peanuts in a low-calcium environment. Gypsum supplied to the rooting
zone did not adequately meet the demands of the developing fruit ; how-
ever, large increases in shelling percentage and yield were observed
when the gypsum was applied to the fruiting medium. Obviously, for

144 THE PEANUT—THE UNPREDICTABLE LEGUME

satisfactory kernel development, it is essential that calcium be supplied to
the zone in which fruit are being formed.

The best method of applying gypsum to peanuts appears to be that of
dusting the material on the plant at the early flowering stage. This rela-
tively soluble source of calcium falls around the plant in the zone of pod
formation and is present at the time when the need for calcium is the
greatest. It is essential that the gypsum be well distributed throughout the
zone of fruit formation. Since there is little residual effect of normal
applications of gypsum (300 to 600 pounds per acre), it is necessary to
make annual additions of this material.

Table 6.—EFFECT OF PLACEMENT OF GYPSUM ON YIELD AND QUALITY OF PEANUTS
on NorFo_k FINE SANDY LoaM, DEEP PHASE, IN 19428. (45)

Percentage | True | Corrected

® Four replications
b Rate = 400 pounds per acre.

As shown in table 5, broadcast applications of lime may be as effective
as gypsum in meeting the calcium requirements of peanuts. However,
these and other data (18, 37, 45) generally indicated that lime applied in
the row at planting may be inferior to gypsum. A satisfactory plan might
be one in which 1,000 to 1,500 pounds of lime are applied broadcast to
the peanuts every 2 to 4 years, the exact amounts and frequency of ap-
plications being governed by soil characteristics. It would appear to be
best to broadcast the lime after the land had been turned but before the
peanuts are planted. By so doing, more of the calcium is concentrated. in
the surface layer and hence should be more effective in supplying the
needs of the developing pods. By applying relatively small amounts of
lime in this manner immediately prior to peanuts in the rotation, it might
be possible to maintain an adequate supply of calcium without increasing
the pH beyond the level where certain minor-element deficiencies are en-
countered.

SOIL FERTILITY 145

I-rrects oF Soi, Propertigs oN CaLciuM REQUIREMENTS

Several studies have indicated that the response of peanuts to calcium
is governed to a large extent by certain soil properties. Attempts have
been made to correlate the level of exchangeable calcium in soils with
response to lime additions. Rogers (95) found that the response of pea-
nuts to lime was related to the exchangeable calcium level of the soil and

Hor Pe °
of OOF pn em mm ne pecccorrcle
° -
x 90F
al3
|i BOF -
= >
le 7or @—e DATA FROM COLWELL ANO
ols BRADY
3/2 60r O—-O DATA FROM ROGERS
a
(a) 5
2 be 50
=
2 5 40
Z 30F CHECK YIELOS AS PER CENT OF
5 THOSE OBTAINED WITH CALCIUM
20-
1OF
iT l ] | l ] l i l l l

0 O02 04 06 08 10 le 14 16 18 20 22
M.E. CA PER !100 GRAMS OF SOIL

Figure 6.—The relationship between lime response and the level of ex-
changeable calcium in the soil. Work by Colwell and Brady (45) was
conducted on Norfolk soils in North Carolina while data by Rogers
(95) was obtained from work with Norfolk soils in Alabama.

indicated that the critical level of exchangeable calcium for peanuts on
Norfolk soils in Alabama was between 0.6 and 0.8 m.e. per 100 grams of
soil. Colwell and Brady (45) also observed a correlation between the
exchangeable calcium level of soils in North Carolina and the response
of peanuts to additions of lime. The relationships between the lime re-
sponse and exchangeable calcium level as reported by Rogers and by
Colwell and Brady are shown in figure 6. It is interesting to note the dif-
ferences in the data obtained by investigators in the two States. Little re-
sponse resulted from liming soils in Alabama which contained more than

146 THE PEANUT—THE UNPREDICTABLE LEGUME

0.7 m.e. of calcium per 100 grams. However, lime response was observed
on North Carolina soils with calcium levels up to approximately 1.4 m.e.
Two factors may have contributed largely to these differences: First,
small-seeded varieties of peanuts were grown in Alabama while the large-
seeded types were used in the work in North Carolina. It has been sug-
gested that large-seeded peanuts have a greater need for calcium than
the small-seeded type. Second, the peanut soils in Alabama are generally
of a lower exchange capacity than those used in North Carolina. The
availability of a given amount of exchangeable calcium might be ex-
pected to increase with a decrease in the base exchange capacity of the
soil.

Rogers (95) pointed out that lime response was more closely corre-
lated with the exchangeable calcium level than with percentage calcium
saturation or with calcium soluble in one-tenth normal hydrochloric acid.
Colwell and Brady also found a better correlation between response to
calcium additions and exchangeable calcium levels than with percentage
calcium saturation of the soil.

Recent investigations at the North Carolina Experiment Station (17,
18, 72, 73) have revealed some very interesting relations between soil
properties and the response of peanuts to calcium. Mehlich and Colwell
(72) studied the absorption of calcium by peanuts as affected by the type
of soil colloid using different levels of exchangeable calcium. These
workers used relatively pure colloidal materials of the 1:1 and 2:1 lattice
types and varied the adsorption capacity by diluting the materials with
quartz sand. With equal concentrations of calcium in sand-clay systems
more calcium was absorbed from the kaolonite or 1:1 type mineral than
from the 2:1 type bentonite. The effect of type of clay on calcium avail-
ability was also evidenced by the quality of the fruit produced (figure
7). A high percentage of filled pods was produced on kaolonitic colloids
even at relatively low calcium levels. In the bentonite systems larger
amounts of calcium were required to produce fruit of similar quality.
These workers observed that the uptake of calcium from kaolonite
systems was more directly related to the total calcium present than to the
degree of saturation. In the systems of 2:1 type mineral the absorption of
calcium was found to be more directly related to the percentage calcium
saturation than to the total amount present.

In a later investigation Mehlich and Reed (73) studied the behavior
of peanuts grown in systems in which the cation-adsorption capacity was
due to both organic and mineral colloids. Kaolonite, bentonite and muck
were used to prepare colloid-sand systems with different cation-ad-

SOIL FERTILITY 147

sorption capacities, different exchangeable calcium levels and different
percentage calcium saturations of the exchange complex. It was found
that at any given level of exchangeable calcium, the quality of fruit was
lower when produced in bentonite or muck. At any given cation-ad-
sorption capacity the percentage of well-filled pods increased with an in-
creasing degree of calcium saturation. Yet, when the percentage calcium
saturations were of the same order the higher calcium levels produced
the better quality of fruit. These workers pointed out that both the per-

=
= 100

@~. LO ttle ates
9--F

gob?) er KAOLIN 24 ME.
‘
/KAOLIN 0.8 ME.

Bor-
i

1O- | BENTONITE 2.4 ME.
‘

60};- 3

so. [BENTONITE 0.8 ME.

30F
20;--
1O-F-

OVARIAN CAVITIES FILLED-PER CE

et
0 02 04 06 08 1.0 12 14 16 18 20 22 24

M.E. CA PER 100 GM.-- COLLOID-SAND MIXTURE

Figure 7.—Percentage ovarian cavities of peanuts filled as affected by type
of colloid, cation-adsorption capacity and calcium level. Mehlich and
Colwelt (72).

centage calcium saturation and calcium level would have to be considered
in determining the need for calcium in peanut soils.

A comparison of the relative availability of calcium in soils of dif-
ferent types of colloids is shown in figure 8. Using the percentage of filled
nuts as a criterion of calcium availability, it is evident that a small amount
of calcium is much less effective in a soil high in organic colloids than ina
soil in which the cation-adsorption capacity arises from kaolonitic-type
minerals. Furthermore, it is evident that greater amounts of calcium

148 THE PEANUT—THE UNPREDICTABLE LEGUME

would be needed for the production of good quality peanuts in soils high
in organic matter or in those containing a large percentage of 2:1 type
minerals.

Studies by Mehlich and Reed (73) of a number of surface soils from
the Coastal Plain areas of North Carolina have indicated that the cation-
adsorption capacity due to organic fraction of the colloids varied between
8 and 70 percent of the total. Such differences in the nature of the col-

l00- TYPE OF COLLOID
E7 EX] KAOLIN —
OQ gol EA] BENTONITE
uJ
=] BB ORGANIC
* 60h
a)
tl
E 40F
>
<
(8)
‘2 20h
1.30 M.E.

EXCHANGEABLE CALCIUM
CATION -ADSORPTION CAPACITY 2.4 ME.

Figure 8.—The effect of the type of soil colloid on peanut fruit quality at different
levels of exchangeable calcium. The percentage of filled cavities may be taken
as a relative index of the calcium availability in the different sand-colloid
systems (94).

loidal material in peanut soils could well explain why soils containing
equal amounts of exchangeable calcium do not respond in a like manner to
additions of calcium materials. Apparently the response of peanuts to
amendments of calcium is influenced greatly by the type of soil colloid
and the percentage calcium saturation as well as by the level of exchange-
able calcium.

MINOR ELEMENTS

Experiments conducted by several of the southeastern experiment
stations have failed to show any widespread response of peanuts to ad-
ditions of different “secondary” and “minor” elements.

There is some evidence that certain minor-element deficiencies may oc-

SOIL FERTILITY 149

cur on soils which have been heavily limed. Batten (29) reported that
peanut yields were reduced by applications of 2,700 pounds of lime, and
recently Shear and Batten (99) initiated a study to determine the cause
of poor growth and a chlorotic condition of peanuts grown on sandy soils
which had been heavily limed. These workers found that the yields of
peanuts on heavily limed soils were increased, by the addition of 20
pounds per acre of MnSO, applied as a side dressing in June or by a
broadcast application of 300 pounds of sulfur before planting. The yield
increases were found to be associated with an increase in manganese up-
take in both cases. The addition of manganese was found to increase the
yield of nuts over the entire pH range studied; however, the beneficial
effect was most pronounced at the higher pH levels (approximately 6.9).
The shelling percentage was found to be decreased by manganese due to
the fact that the growth period was extended, resulting in more immature
nuts at harvest time.

Nelson (81), in North Carolina, has also observed “overliming in-
jury” in peanuts, apparently resulting from a deficiency of manganese.
An example of such injury is shown in figure 9.

Workers (1) at the Alabama Experiment Station report that appli-
cations of different combinations of 10 pounds of zinc sulfate, 5 pounds of
borax, 25 pounds of manganese sulfate, and 5 pounds of copper sulfate
per acre to a Norfolk sandy loam failed to increase the yield of Spanish
peanuts.

The following elements were added to a Norfolk sandy loam in an
experiment conducted by the Georgia Experiment Station (6): Sulfur,
40 pounds; manganese, 25 pounds; magnesium, 75 pounds; zinc, 10
pounds; copper, 10 pounds; boron, 5 pounds*. None of these materials
applied alone or in combination with 500 pounds of limestone gave an in-
crease in yield of nuts or hay. In another experiment conducted in a
“sulfur-deficient area,’ Futral (6) reported that sulfate of ammonia was
superior to nitrate of soda for Spanish peanuts and suggested that this
superiority was due to a sulfur response.

A summary of experiments conducted on several soils in north
Florida (5) shows little effect of additions to peanuts of a minor element-
mixture containing 10 pounds of copper sulfate ; 10 pounds of magnesium
sulfate ; 5 pounds of zinc sulfate ; and 5 pounds of borax. Harris (57) has
recently reported that peanuts grown on an Arredondo loamy fine sand
in Florida developed abnormal characteristics which were corrected by

*The rates reported in this experiment were probably for the salt containing the element rather
than the amount of the element itself, a possible exception being sulfur.

150 THE PEANUT—THE UNPREDICTABLE LEGUME

Courtesy North Carolina Agricultural Experiment Station (81)

Figure 9—“Overliming injury” with peanuts, resulting apparently from a deficiency
of manganese. The stunted, chlorotic plants in the center of the picture were
growing on soil at pH 7.7 while the soil in the surrounding area was at pH 5.9.
Such injury has been observed on soils as low as pH 6.4.

additions of copper to the soil. Applications of 10 pounds per acre of
cupric chloride to the soil were found to increase the yield of both nuts and
foliage and improved the grade quality of peanuts.

Collins and Morris (43) report that tests with iron, magnesium,
copper, borax, manganese and zinc in 12 experiments in North Carolina
over a 3-year period show little evidence that these elements were limit-
ing factors in the production of peanuts.

Piland, Ireland and Reisenauer (88) studied the effect of additions
of 5 pounds of borax on the quality of peanuts at 17 different locations in
North Carolina. The average of the results showed that boron had a
slight tendency to reduce the shelling percentage. However, the per-
centage of large nuts was increased significantly by the addition of borax.

Sommer and associates (101, 102) in greenhouse studies with several

SOIL FERTILITY 151

Alabama soils observed marked increases in nut production from the use
of magnesium. However, the soils had been subjected to very intensive
cultivation prior to planting peanuts, and the responses were undoubtedly
exaggerated because of abnormally low magnesium levels. These workers
reported that little benefit was obtained from the addition of minor ele-
ments to peanuts.

VARIETAL DIFFERENCES IN RESPONSE
TO FERTILIZATION

Many studies have: indicated that peanut varieties exhibit marked
differences in response to fertilization. Several workers (10, 106) have
suggested that the so-called small-seeded types were more responsive to
additions of N, P and K, whereas the large-seeded types might be ex-
pected to respond more to Ca amendments. However, there appear to be
decided differences in the nutritional requirements of varieties within |
either of the different major types. Such differences might limit broad
generalizations regarding the response of any given type of peanut to
fertilization.

McClelland (68), in Arkansas, reported the results of experiments
in which a number of different varieties and strains of the major types
of nuts were grown with and without additions of limestone. The results
are shown in table 7. Strains of Spanish peanuts were found to differ
greatly in response to lime. Greater increases in yields of hay and nuts
were obtained with improved Spanish and Spanish Selection than with
any of the small runner or large-seeded types. The yield of Virginia
Jumbo, a large-seeded type, was initially very high and was slightly re-
duced by the lime.

The 5-year average results of an experiment conducted on a Norfolk
sand at the Florida Experiment Station (65) are shown in table 8.
Several different varieties and strains of both the large- and small-seeded
type peanuts were grown with and without additions of 600 pounds of
gypsum. The average results show little response of small-seeded varieties
or of Virginia Bunch, a large-seeded variety, to this calcium-bearing ma-
terial. The yields of Jumbo variety were increased by adding gypsum,
while this material tended to decrease the yields of Virginia Runner, also
a large-seeded type. Therefore, although one of the large-seeded varieties
appeared to benefit from the gypsum, it is not possible to conclude from
this experiment that, as a group, the large-seeded peanuts were any more
responsive to amendments of calcium than were the small-seeded
varieties.

152 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 7.—EFFECT OF LIME UPON YIELDS OF SEVERAL VARIETIES OF PEANUTS.
ARKANSAS EXPERIMENT STATION,® 1940. (68)

No Lime Lime* Gain with Lime
Variety and
treatment Peanuts | Hay | Peanuts Hay Peanuts Hay
per acre | per acre| per acre | per acre| per acre | per acre
Pounds Tons Pounds Tons Pounds Tons
Spanish............. 3,353 3.76 3,564 4.29 211 0.53
Improved Spanish....}| 2,508 2.90 4,462 5.94 1,954 3.04
Spanish Selection....] 2,429 2.71 “4488 5.28 25059 2.57
Red Spanish (1)..... 2,429 2.71 3,221 3.70 792 0.99
Red Spanish (2)..... 3,036 3.37 3,300 3.63 264 0.26
Valencia............ 2,561 2.84 2,851 3.23 290 0.39
Tennessee Red (1)...] 1,716 2.11 2,376 3.04 660 0.93
Tennessee Red (2)...| 3,300 4.22 3,828 5.08 528 0.86
Virginia Red........ 2,112 2.51 3,168 3.96 1,056 1.45
White Virginia...... 528 .79 1,584 2.05 1,056 1.26
Virginia Jumbo...... 4,488 5.28 4,224 5.02 — 264 —.26
Jumbo; 05sec e608. 2,006 2.77 2,719 3.43 713 0.66
~ \ 7 fo 5

* Applied in the row before planting at the rate of 880 pounds of air-slacked lime per acre.

b Hay yields include weights of nuts.

© No information was presented relative to the experimental design, replications, or the magnitude
of differences which might be considered to be significant.

4 Bolivar silt loam, pH = 5.42-5.65.

Table 8.—EFFECT OF GYPSUM ON YIELD OF SEVERAL PEANUT VARIETIES. NORFOLK
SAND. FLoRIDA AGRICULTURAL EXPERIMENT STATION. (65)

5 Year Ave.» 1923/24/25 /26/28

Variety Gypsum* No Increase Over
Gypsum No Gypsum
Pounds Pounds Pounds
per Acre per Acre per Acre
Spanish (Florida)................6. 661 647 14
Spanish (Improved)............... 618 580 38
Valencia awoscaeies aslede dias s cera tide 591 552 39
Va: Bunhssecs 24 aause eaves sine ed ae 994 930 64
Va. Runner .c. .5 coaeaads chee eae 801 950 —149
JUMBO ssa ied eld ke. bscce soeiscslace: saan Wastes 1,100 786 314
Pela, RGAE Rs. ic eases auavice ok dene alec ovn 1,047 995 52

= Gypsum applied as top dressing at the rate of 600 pounds per acre as peanuts started to bloom.
b The 1927 peanut crop was destroyed by rodents. Continuous peanuts on the same plots from 1923

to 1928. All plots planted to oats in fall of year and turned in spring several weeks before peanut planting.
° The Virginia Runner was not in the test in 1923 and cdnsequently has a 4-year average.

SOIL FERTILITY 153

Stokes and Camp (104), working in Florida, have reported that
gypsum gave profitable increases in yields of Florida runner and a Jumbo
variety, but not of the Spanish, Valencia and Virginia Bunch varieties.

Experiments conducted at several locations by workers at the North
Carolina Station (46) show considerable differences in response of the
large- and small-seeded type peanuts to additions of lime and gypsum.
On soils extremely low in calcium, the Virginia Bunch variety, a large-
seeded type, was found to respond more to additions of gypsum than a

small runner and White Spanish varieties. On soils high in calcium the
response was quite erratic and no general trends were observed.

A detailed study by Middleton, et al. (74) of the behavior of four
varieties of peanuts as affected by calcium and potassium variables re-
veals some interesting variety-fertility interrelations. Some of the results
of this study are shown in figure 10. It is evident that the relative behavior
of the four varieties depended upon the fertilizer treatment. For example:
Without treatment the Spanish varieties yielded highest and the Virginia
Bunch yielded lowest. However, when all varieties received gypsum, the
yield of Virginia Bunch was the highest. The authors concluded that the

YIELD EXPRESSED IN POUNDS PER ACRE
SHELLING 60 PER CENT

G =400 POUNDS OF GYPSUM

GK GK = 400 POUNDS OF GYPSUM PLUS 45
POUNDS OF K20

O KS
& me
a Rs Ses
VIRGINIA N.C. SPANISH WHITE
BUNCH RUNNER 2B SPANISH

Figure 10.—The relative yields of four varieties of peanuts grown with and without
amendments of gypsum and potash. Gypsum applied to foliage at early bloom-
ing; potash applied as top dressing at emergence. Soil, Norfolk sand; pH =
4.6; 0.54 m.e. exchangeable calcium; 0.04 m.e. exchangeable K. Source: Middle-
ton, Colwell, Brady, and Schultz (74).

154 THE PEANUT—THE UNPREDICTABLE LEGUME

Spanish varieties might be better suited to soils low in calcium than the
Virginia Bunch unless proper steps were taken to supply adequate
calcium.

These workers at the North Carolina Station also point out that from
one experimental location to another the effects of the fertilizer treat-
ment on a particular variety were more consistent than the relative yields
of the four varieties receiving the treatment. It was suggested that even
when the calcium and potassium requirements were met some other
factor apparently influenced the yield of one variety more than another.
In view of the fact that the Spanish variety performed relatively better
on soils with high organic-matter levels, it was suggested that there
might have been a differential response to nitrogen.

Middleton and Farrior (75) reported that the Virginia Bunch
variety performed better on some North Carolina soils than did the
Jumbo Runner, whereas the reverse was true on other soils. These
workers also observed that the large-seeded varieties appeared to respond
more to the use of gypsum than did the small-seeded types.

The results of experiments conducted on a Norfolk loamy fine sand
in Georgia are generally in agreement with the findings of the North
Carolina workers. Investigators (6) at the Georgia Station found that a
Spanish variety showed little response to additions of lime or gypsum
while the yields of Carolina Runner, Virginia Bunch and Virginia Run-
ner were increased by both materials. Without calcium amendments, the
Spanish variety yielded more than did either of the Virginia varieties.
With additions of lime and gypsum the relative order was changed.

Differences in response of varieties to applications of nitrogen are
shown in table 3. Results of experiments conducted by the staff of the
Alabama Experiment Station show that relatively large increases were
obtained from additions of nitrogen to a Spanish variety, whereas the
higher rates of nitrogen were of less value with a “runner” variety. Gore
(55) in Georgia has also found the North Carolina Runner peanut to be
less responsive to nitrogen amendments than a Spanish variety.

At first glance some of the variety-fertility interaction data in the
literature appear to be quite anomalous. Some of the experimental data
would indicate that one type or variety is most responsive to a given nu-
trient at one location and least responsive at another. It is quite possible
that even though some of the older varieties used in experiments con-
ducted at different locations were the same in name, they may have been
distinctly unlike genetically. If such genetic differences did exist, it should
not be surprising if the behavior were not the same in view of the marked

SOIL FERTILITY 155

differences in lime response which have been observed with strains of
the same variety (table 7).

Some of the experimental evidence might suggest that the differences
in response of varieties or types of peanuts to fertilization are, to a cer-
tain extent, a function of seed size. Such may be the case, or the unequal
response to fertilization may be due to other genetic differences not as-
sociated with kernel size. At any rate, it is fallacious to attempt to classify
all peanut varieties in two categories, a large-seeded group and a small-
seeded group, because of the gradation in kernel size, with no sharp differ-
entiation which would permit such broad groupings. Certainly the dif-
ferences in seed size and behavior of peanut varieties within either of
the so-called major-size groups would limit generalizations as to their re-
sponsiveness to fertilization.

Considering the differences in varietal response to fertilization, it
is very evident that research programs in peanut breeding and soil fer-
tility should be inseparable. In comparative tests of several varieties, it
has been demonstrated that an apparently superior variety may be defi-
nitely inferior under different environmental conditions. Therefore, in
evaluating peanut varieties, it is essential that they be grown at different
levels of soil fertility and under other variations in environmental con-
ditions. The fact that many of the present peanut varieties appear to be
relatively unresponsive to fertilization does not preclude the possibility
that varieties may eventually be developed which would respond to
fertilizer amendments much in the same manner as do many other crops.

ROTATION AND MANAGEMENT PRACTICES AND THE
MAINTENANCE OF SOIL FERTILITY

Several factors combine to make the problem of maintaining the fer-
tility of peanut soils especially acute. First, the native fertility of the soils
used for growing peanuts is relatively low. Furthermore, peanuts remove
relatively large amounts of certain nutrients from the soil with the normal
systems of management in which both hay and nuts are harvested. Since
peanuts have not been found to be as responsive to direct applications of
fertilizer materials as are many other crops, there is a tendency to supply
much less of certain nutrients than is removed from the soil by the crop.
Considering these factors, the problem is resolved to one of determining the
most effective and economical manner of obtaining high yields of peanuts
and other crops grown in rotation with them and, at the same time, main-
taining the fertility of the soil.

156 THE PEANUT—THE UNPREDICTABLE LEGUME

ConTINUOUS CROPPING WiTH PEANUTS

Farmers have long recognized the fact that it is not desirable to plant
peanuts year after year on the same soil. The harmful effect of continuous
cropping with peanuts was aptly illustrated in a study conducted at the
Georgia Coastal Plain Experiment Station (table 9). In an experiment
in which continuous peanuts were fertilized with different combinations
of N, P and K it was found that with all fertilizer treatments there was a
progressive decline in yields with each successive crop of peanuts. There
was little effect of withholding nitrogen or phosphorus from the complete

Table 9.—THE YIELDs OF SUCCESSIVE CROPS OF PEANUTS GROWN WITH AND WITHOUT
ADDITION OF FERTILIZERS. GEORGIA COASTAL PLAIN EXPERIMENT STATION (11).

Yield unshelled nuts per acre
Treatment
1940 1941 1942 1943 1944
pounds pounds pounds pounds pounds
No fertilizer... ........ 1407 1259 804 663 488
OSS iiss cur tahssa gtais' aaa 1645 1585 1169 1088 1037
3-0-8. 6s vecypaeey hae 1744 1647 1303 1125 1106
3-8-Oleexa ei ad cay acne 1628 1410 1013 910 531
SO r Bis os cdckg tie Sadun ess 1701 1603 1272 1150 1075

8 500 pounds fertilizer per acre.

fertilizer ; however, the yields were markedly reduced when no potassium
was added. Apparently the lack of potash was the factor primarily re-
sponsible for the poor yields on the nonfertilized soil. Perhaps the yields
could have been maintained at higher levels on the plots receiving the
complete fertilizer had more than 40 pounds of potash been applied.

Work conducted at the Alabama Experiment Station (2) further
demonstrates the harmful effect of planting peanuts continuously on the
same soil. It was found that the yield of cotton planted after 7 successive
years of peanuts was only 345 pounds despite the fact that the cotton
received 600 pounds of 6-8-8 fertilizer. At the same time, plots which had
been planted to continuous cotton during this period and fertilized with
600 pounds of 6-8-4 yielded 1,269 pounds of seed cotton. Peanut yields
apparently had begun to decline also after 6 years of continuous cropping
with peanuts.

It would indeed be difficult to maintain the fertility of peanut soils
through such a program of continuous cropping and inadequate fertili-
zation. There is no evidence, however, which would indicate that the

SOIL FERTILITY 157

productivity of peanut soils could not be maintained if sufficient ferti-
lizers are supplied to compensate for the nutrients removed by the crop.
Yet, such a program of continuous cropping and heavy fertilization would
undoubtedly not be economical. Furthermore, even though the fertility
could be maintained, it would not be advisable to make successive plant-
ings of peanuts on the same land because of the likelihood of more severe
disease and insect infestation.

Crops Grown IN Rotation WitH PEANUTS

A number of crops such as corn, cotton, tobacco, soybeans, potatoes,
grain sorghum, truck crops, cereals and legumes are well suited for use
in rotations with peanuts. While there is little information relative to ro-
tation requirements, it is generally recommended that peanuts not be
grown on the same soil more than once every 3 or 4 years.

Beattie and Beattie (33) of the U. S. Department of Agriculture have
suggested that peanut rotations should include at least two soil-building
crops, one of which is a winter cover crop. Batten (30) considers the
chief requirement of a peanut rotation to be that it should furnish a con-
siderable amount of organic matter to be incorporated with the soil. Gore
(54) at the Georgia Experiment Station reports that peanuts do espe-
cially well following well-fertilized cotton, tobacco or truck crops. This
investigator reports that the only objection to rotating cotton with pea-
nuts is the tendency for Sclerotium rolfsti to be more severe. It was re-
ported that growers also found considerable disease in peanuts following
cowpeas. The North Carolina Station has recommended that peanuts
should not follow soybeans on soils where Sclerotium rolfsit is present.

The majority of the experimental work with peanuts indicates that
little response may be expected from fertilizing peanuts if they are grown
in rotation with other well-fertilized crops. The results from five rotation
experiments conducted in North Carolina (19, 20) for a period of 6 years
show that the application of 100 pounds of muriate of potash to cotton
preceding peanuts resulted in as high peanut yields as did the application
of 50 pounds to each crop. Furthermore, the yields of cotton were in-
creased upon receiving all of the potash. The result of these and other
(16, 18, 100) experiments suggests that instead of fertilizing peanuts
directly it would be better to use relatively large amounts of fertilizers
with other crops in the rotation which would respond to the additional
fertilizer.

Experiments conducted by the Alabama Station (2) indicate that the
normally recommended rates of fertilizing a crop such as cotton are inade-

158 THE PEANUT—THE UNPREDICTABLE LEGUME

quate when the crop is grown in rotation with peanuts. The results of
experiments, reported in table 10, show that when two crops of peanuts
were harvested during a 7-year period in a corn, cotton, peanut rotation,
the fertility of the soil was depleted to such extent that the cotton yields
were approximately one-half of those obtained on soil which had been
planted to continuous cotton. The injurious effect of the two harvested
crops of peanuts was overcome somewhat by applying more potash to the
cotton.

Table 10.—THE INFLUENCE OF PEANUTS IN A ROTATION WITH COTTON AND CoRN
UPON THE YIELDS OF CoTTON. ALABAMA AGRICULTURAL EXPERIMENT STATION (2).

Year

Yield of cotton
in corn, cotton,
peanut rotation®

Vield of cotton
in corn, cotton,
peanut rotation»

Yield of cotton
in a continuous
cotton rotation®

Pounds per acre

LOSS specs ciiape neces) 1696 1622 1406
1936. cei eae en aes 1368 1298 1366
BOS Os ces) au cnger atkins 652 1075 1269

® Cotton fertilized with 600 pounds 6-8-4; corn and peanuts unfertilized.

» Cotton fertilized with 600 pounds 6-8-4 in 1933 and 1936; 600 pounds 6-8-12 applied to cotton in
1936. Corn and peanuts unfertilized.

° Cotton fertilized yearly with 600 pounds 6-8-4.

d The experiment was initiated in 1932.

LEGUMES AND NONLEGUMINOUS CovER Crops IN PEANUT ROTATIONS

Very little plant residue is returned to the soil from a crop of peanuts ;
thus, as normally harvested, peanuts remove considerable quantities of
inorganic nutrients. Furthermore, when peanuts are harvested the soil is
left completely bare for several weeks during late summer and fall, pro-
viding conditions favorable for the rapid oxidation of the soil organic
matter. Certainly it would be difficult to maintain the productivity of
peanut soils unless measures were taken to replenish the supply of organic
matter. Green manure crops are well suited to peanut rotations and their
use may help maintain an adequate level of organic matter in soils.

Numerous experiments have been conducted to determine the effect
of legumes and nonleguminous cover crops upon the yield of peanuts.
Investigators at the Alabama Station (1) have studied the effect of vetch
and oats upon the yield of continuous peanuts, and the results are re-
ported in Table 11. These data show that the addition of phosphorus and
potash to peanuts resulted in a 50-percent increase in yields. When vetch
was grown and fertilized with P and K, the yields of peanuts were more

SOIL FERTILITY 159

than doubled. Oats, unfertilized and turned under while green, increased
the yields some 250 pounds. The addition of nitrogen to the oats resulted
in a further increase in yield of 275 pounds, suggesting that part of the re-
sponse to the vetch was due to the nitrogen supplied by the legume.
Vetch appeared to have little influence on peanut yields when grown prior
to cotton in a peanut, vetch, cotton rotation.

Table 11—TuHE Errect or GREEN MANURE CROPS ON THE YIELD OF SPANISH
PEANUTS. EXPERIMENTS CONDUCTED AT AUBURN, ALABAMA, ON A NORFOLK SANDY
Loam Solu (1).

Vield of Peanuts
pounds per acre

Number Cropping System Fertilizer* 4-year average
1943-46
1 Continuous peanuts............... None 626
2 Continuous peanuts............... P-K 985
3 Continuous peanuts with vetch..... P-K 1364
4 Continuous peanuts............... N-P-K 972
5 Continuous peanuts with oats as
green manure crop.............. None 851
6 Continuous peanuts with oats as
green manure crop.............. N 1121
7 2-year rotation—cotton........... P-K
peanuts.......... P-K 1094
og
8 2-year rotation—cotton........... P-K
peanuts.......... P-K
VOtChiss is wees Sere P-K 1095

®N = 36 pounds nitrogen from nitrate of soda.
P-K = 300 pounds 0-14-10 per acre.

Workers (15) in North Carolina have studied recently the effect of
several different cover crops upon the yields of peanuts in a cotton-peanut
rotation. The results are shown in figure 11. The legumes were found to
increase the yields of peanuts an average of 40 percent. It was concluded
that the increase was not due to the nitrogen supplied by these crops since
the yields of the “no-cover” plots were not affected by the addition of
60 pounds of nitrogen. Yet, as seen in figure 11, ryegrass was not as effec-
tive as were the legumes. These investigators indicated that turning under
large amounts of winter cover crops prevented packing and left the soil
in better physical condition. Penetrometer measurements indicated that
the soil in the vetch plots was more easily penetrated than in the “no-

160 THE PEANUT—THE UNPREDICTABLE LEGUME
1600,-

u
a
rw) g
<
a ”
a 1200 <
=) | ew
a
' —- ul
Va) a >
bE Ww o,
2 800} + for TER Oe
< oO 2) =
my) te aj ro < = 4
a. > Wo a fo}
ro} >be G) z n pa
re w) Os < UO
oO 400F O z 2 -
° ot bs Eo & >
a a Zz Zo x 3 e
7 <
u
= (0)

WINTER COVER CROPS PRECEDING PEANUTS
Courtesy North Carolina Agricultural Experiment Station (15)

Figure 11—The effect of different winter cover crops upon the yield of Virginia
Bunch peanuts. (3-year average).

cover” plots. It is essential that peanut soils be in good physical condi-
tion because the pegs must penetrate the surface soil in order for nuts to
be formed.

Errect oF MEetHops oF HARVESTING PEANUTS ON SoIL DEPLETION AND
GROWTH OF SUCCEEDING CROPS

A large percentage of the peanuts grown in the United States is har-
vested for market by removing both nuts and vines from the soil. As dis-
cussed previously, such a system of management is known to remove
large quantities of nutrients and to lower the productivity of the soil. In
some sections of the Southeast, the practice of harvesting the peanut crop
by grazing hogs (hogging-off) is followed. With such a practice most of
the nutrients are returned to the soil in the plant residues and animal
manures. Peanuts handled in this manner may serve as a soil-building
crop.

Results of studies conducted at the Wiregrass Experiment Station in
Alabama with different cropping systems including hogged and dug pea-
nuts are shown in table 12. Peanuts planted continuously on the same
soil, unfertilized and harvested by hogs, were found to yield quite satis-
factorily . . . as well, in fact, as those grown in rotation with fertilized

SOIL FERTILITY 161

Table 12.—Y1ELDS oF Cotton, CORN AND PEANUTS IN CROPPING SYSTEMS THAT
INcLUDE HoccEp anp DuG PEANUTS. WIREGRASS SUBSTATION, HEADLAND, ALA-
BAMA, 1939-1946, INCLUSIVE (1).

TiFTon FINE SANDY LoAM

Crop-
ping Crop Fertilizer* Average Vield
system 1939-46
Pounds seed cotton
and peanuts,
Bushels corn

1 * Peanuts—Dug.............00008- 0 602

2; Peanuts—Hogged................ 0 1524

3 Peanuts—Dug...........0.0000e 0-8-8 1455
Cottonia:.: sc% ose va ver eeme tes eees 6-8-8 975

4 Cottons schaeaes anda abbots 6-8-4 1207
Peanuts—Dug.........-.-0.0005- 0-8-4 1627

5 CottOnssisedsceeyssaeecas cig ee aes 0-8-4 1380
Peanuts—Hogged.............06. 0 1791

6 COttOfas cesaies Gelade oes Hae 6-8-4 1416
7 Com vac nio ives iach erdesdteg sss 0 10.0

8 Corti os cucthee ant cites Da Hietedeats 6-8-4 33.3

9 Cont. 2 cer sanevtieawiand « eeteeatiad he 0-8-4 23.0
Peanuts—Dug.........eeseeeeees 0-8-4 1640

10 Commis: sy ae eaeaes ge tates oe eer 0-8-4 40.6
Peanuts—Hogged..............-. 0-8-4 1777

11 COP 2.3 db cnee ei alee silico nas 0 42.1
Peanuts—Hogged................ 0 1744

COttONes ao has Gk ica dade exer aa 6-8-4 1384

12 Peanuts—Dug 0 1507
Corn 0 20.6

Cotton 6-8-4 799

13 Peanuts—Dug...........-..00005 0 1566
COP ie cask nad eldnehe esas Ha ie HE Gs 0 25.6

COPLOM a ieioled a. neeleaccuetce tienlaleranicee et 6-8-12 1176

a 600 pounds per acre. Cotton received 6-10-4 and all other crops no fertilizer. 1932-1938.

cotton or corn and dug. Higher yields were obtained, however, when
the hogged peanuts were grown in rotation with a fertilized crop of corn
or cotton. The yield of corn grown in rotation with hogged peanuts was
some 17 bushels greater than when rotated with dug peanuts. Cotton
yields were also much greater in rotation with hogged peanuts. The

162 THE PEANUT—THE UNPREDICTABLE LEGUME

higher yields of crops following hogged peanuts were probably due in
part to the nitrogen returned to the soil in plant residues.

Other experiments in Alabama (2) have shown that when peanuts
were dug the yields of the succeeding crops were decreased, but when
harvested by hogs the yields of the following crops were increased. Thus
the method of harvesting may determine whether peanuts are soil deplet-
ing or whether they may actually increase the productivity of the soil.

Table 13.—INTERPLANTED CORN AND PEANUTS IN A COoRN-COTTON ROTATION.
ALABAMA AGRICULTURAL EXPERIMENT STATION (1).

Yields per acre

Cropping® Seed cotton Corn Peanuts>
Pounds Bushels Pounds

Brewton Field*, 1938-1946

Cotton; COM 4005.0 eapeiw headers ioe hs 551 12.9 —
Cotton, corn and peanuts............ 741 11.8 394

Prattville Field, 1932-1946

COLT COs aie wend seek eee ha ed 597 13.7 —
Cotton, corn and peanuts............ 840 10.8 794

Tennessee Valley Substation®, 1932-1945

Cotton; COrn. 2 ccekeee aa aedcn es 1,129 27.8 —
Cotton, corn and peanuts............ 1,283 23.4 841

a All rows 3% feet apart; alternate rows in corn, and peanuts. All fertilizers, 600 pounds per acre
0-10-4, apolied to cotton.

b Runner peanuts all years—vines returned to the land at Brewerton and Prattville,

° Kalmia fine sandy loam.

4 Greenville fine sandy loam,

® Dewey silt loam.
It should be pointed out that the differences in yields of crops following
peanuts harvested by the two methods would undoubtedly be smaller
were more fertilizer applied to the dug peanuts to compensate for the
nutrients removed by the crop. Thus it appears likely that the produc-
tivity of these soils could be maintained to a large extent through ade-
quate fertilization.

While the peanut is considered to be one of the most soil-depleting
crops grown in this country, there is nothing unique in the ability of this
crop to reduce the productivity of soils. Other crops would undoubtedly
be equally as injurious were they harvested as peanuts normally are. In
some sections of the world, notably in certain localities in Africa, the tops
are left on the soils after the nuts are picked. When such a practice is fol-

SOIL FERTILITY 163

lowed the problem of maintaining the fertility of peanut soils is much less
acute. In view of the fact that a large percentage of the nutrients absorbed
by the peanut plant is found in the tops (table 1), the removal of the hay
from peanut soils becomes a questionable practice. This is especially true
because the organic-matter level of many soils used for growing peanuts
is critically low and could, in part, be replenished were the peanut vines
returned to the soil.

The practice of interplanting peanuts with corn has been followed in
some localities. One or both crops may be harvested for market or may
be hogged-off. Experiments at three locations in Alabama were conducted
to study the effect of interplanting corn and peanuts upon the yield of
cotton and corn grown in a 2-year rotation. The results of these tests
(table 13) show that the yields of cotton were higher following inter-
planted corn and peanuts than when grown after corn alone. Further-
more, the value of the interplanted corn plus peanuts was considerably
greater than the corn grown alone. It should be pointed out that the
greatest increases in cotton yields were observed at the two locations
where the peanut vines were returned to the land.

SUMMARY

There appears to be universal agreement on what constitutes an
“ideal” soil for growing peanuts. A soil well adapted to the production of
this crop has been characterized by many as a well-drained, light-colored,
loose, friable sandy loam, well supplied with calcium and with a moderate
amount of organic matter.

A study of the soil-fertility investigations with peanuts reveals a mul-
titude of inconsistencies. Many workers have indicated that the peanut
plant is quite unpredictable in its response to fertilization. While such
would often appear to be the case, it seems that many of the apparent
anomalies associated with the fertilization of peanuts have arisen through
failure to evaluate fully the environmental conditions under which the
experiments were conducted. Furthermore, due consideration must be
given to the unique growth and fruiting habits of the peanut in interpret-
ing experiment results. Recent fundamental studies dealing with the nu-
trition of peanuts have been very helpful in interpreting some of the pea-
nut fertility research data. More of such investigations are greatly needed.

Most southern experiment stations currently recommend that peanuts
be grown following other well-fertilized crops. When such a practice is
followed, much of the experimental evidence suggests that little may be
gained from additions of nitrogen, phosphorus or potassium directly to

164 THE PEANUT—THE UNPREDICTABLE LEGUME

the crop. There is some evidence that certain varieties of peanuts may
respond to relatively large additions of nitrogen, despite the fact that the
crop is a legume. However, large quantities of nitrogenous fertilizers are
not commonly applied to peanuts. Unless the crops grown in rotation
with peanuts receive very liberal applications of potassium, it may be
necessary to apply some fertilizers containing this element directly to the
peanuts in order to obtain maximum yields and to maintain the fertility
of the soil.

The importance of calcium in the nutrition of peanuts has long been
recognized. Generally the response of peanuts to amendments of calcium
has been more consistent than to additions of any other nutrient. Appar-
ently one of the primary functions of calcium in peanut nutrition is to
improve the quality of the nuts, or more specifically, to aid in the devel-
opment of the kernel. The better quality of nuts grown in soils well sup-
plied with calcium is evidenced by a lighter, firmer hull and few unfilled
pods (pops).

One of the most common methods of supplying the calcium needs of
peanuts is to apply gypsum to the foliage at early blooming. However,
when the soil has been limed adequately little benefit may be derived from
additions of gypsum. For a number of reasons, it would appear better to
maintain an adequate calcium level in peanut soils through the use of a
liming material rather than by additions of a neutral salt such as gypsum.
Calcitic lime should be superior to one high in magnesium.

Some investigators have obtained a fair correlation between the ex-
changeable calcium levels in soils and the response of peanuts to amend-
ments of lime or gypsum, and expected responses have been predicted on
such a basis. However, for a more exact estimate of the need for calcium
in peanut soils, the nature of the soil colloids and the percentage base
saturation, as well as the exchangeable calcium level, need to be con-
sidered.

There is little evidence that any of the so-called “secondary” and
“minor” elements are normally limiting the yield of peanuts, except per-
haps on heavily limed soils where deficiencies of manganese may occur.

A review of peanut-fertilization research suggests that too little atten-
tion has been given to the method of placement of peanut fertilizers.
Studies have shown that in order for calcium to be most effective it
should be localized in the zone in which the pods develop. On the other
hand, a high concentration of potassium in the fruiting zone may be
harmful because of its effect on fruit quality, especially at low-calcium
levels. Furthermore, fertilizer materials, if placed too close to the seed at

SOIL FERTILITY 165

planting, may impair germination. Perhaps fertilizer materials would be
found to be more beneficial if a greater effort were made to use them
properly.

There is much evidence that peanut varieties exhibit marked differ-
ences in their response to certain nutrients. Furthermore, strains within
a given variety have been found to differ greatly in response to fertiliza-
tion. These differences may account in part for some of the existing con-
fusion regarding the fertilization of peanuts. Certainly the plant breeder
must give ample consideration to such differences in evaluating peanut
varieties.

Peanuts remove relatively large amounts of certain nutrients from the
soil with the normal systems of management in which both hay and nuts
are harvested. Yet, because of the fact that peanuts have not been found
to be as responsive to direct applications of fertilizer materials as other
crops there is a tendency to supply less of some nutrients than is removed
from the soil by the crop. It is by no means a desirable practice to grow
peanuts continuously on the same soil. Many experiment stations recom-
mend that they not be grown more than once every 3 or 4 years. Peanuts
may be grown satisfactorily in rotation with a number of different crops.
Generally, it would be desirable to grow well-fertilized crops such
as cotton, tobacco or truck crops immediately prior to peanuts in the
rotation.

Little organic matter is returned to the soil from a crop of peanuts.
Furthermore, after peanuts are harvested conditions are quite favorable
for the rapid oxidation of the organic matter present in the soil. Legumin-
ous green manure crops are well suited to peanut rotations and their use
may help to maintain an adequate level of organic matter and insure a
good physical condition. It is especially important that peanut soils be
kept loose and friable because the pegs must penetrate the surface in
order for nuts to be formed.

With the normal methods of harvesting, peanuts are considered to
be one of the most soil-depleting crops grown in this country. However,
when the crop is harvested by grazing hogs or when the nuts are picked
off and the vines returned to the soil peanuts may actually increase the
productivity of the soil. Therefore, there appears to be nothing unique
about the soil-depleting powers of the peanut as some have indicated.

It has been suggested (42) that large increases in peanut yields
cannot be expected from fertilizer treatments as only the nuts produced
in a relatively short period of continuous blooming of the plant can be
saved at harvest. However, even though direct responses to fertilization

166 THE PEANUT—THE UNPREDICTABLE LEGUME

may not be pronounced, it is reasonable to expect increased yields of
peanuts through the introduction of better varieties, by the more
effective control of diseases and insect pests and through the adoption of
better cultural practices such as the use of closer spacing. As such
yield increases are realized and as more nutrients are removed from the
soil by the harvested crop, the problem of maintaining the fertility of
the peanut soils will undoubtedly become increasingly acute. It is likely
that more fertilizers may eventually have to be applied to peanuts or
to the other crops grown in the rotation if the productivity of peanut
soils is to be maintained.

(1) ANON.

1947,

(2)

1939,

(3)

1937.

(4)

1934,

===

1947,

——

1947.

rrr

1947.

(8)

1946.

OO) =

1944,

(10) ———

1944,

(11) ———

1946.

(2) ———

1944.

(13) ———

1942.

SELECTED REFERENCES
UNPUBLISHED DATA. Ala. Agr. Expt. Sta.

THE EFFECT OF “‘DIGGING”’ AND ‘‘HOGGING’’ PEANUTS ON COTTON YIELDS,
Ala. Agr. Expt. Sta. Leaflet No. 18.

FERTILIZER AND CROP EXPERIMENTS ON CERTAIN SOILS OF THE BLACK
BELT. Ala. Agr. Expt. Sta. Cir. 78.

PEANUTS. Ala. Agr. Expt. Sta. Leaflet No. 5.
UNPUBLISHED DATA. No. Fla. Expt. Sta.
UNPUBLISHED DATA. Ga. Agr. Expt. Sta.

FERTILIZER AND AMENDMENTS FOR PEANUTS. Ga. Agr. Expt. Sta. Ann.
Rpt. 59:23-25.

Ga. Agr. Expt. Sta. Ann. Rpt. 58:28.

DIFFERENCES IN Sclerotium rolfsii ON SPANISH PEANUTS CAUSED BY
FERTILIZER TREATMENTS. Ga. Agr. Expt. Sta. Ann. Rpt. 56:17.

FERTILIZERS AND AMENDMENTS FOR PEANUTS. Ga. Agr. Expt. Sta. Ann.
Rpt. 56:17-20.

PEANUT FERTILITY TESTS. Ga. Coastal Plain Expt. Sta. Ann. Rpt. 26:
16-17.

PEANUT FERTILIZER STUDIES. Ga. Coastal Plain Expt. Sta. Ann. Rpt.
24:25-27,.

PEANUT FERTILIZERS. Ga. Coastal Plain Expt. Sta. Ann. Rpt. 22:31-35.

UNPUBLISHED DATA. Miss. Agr. Expt. Sta.

SOIL FERTILITY 167

(15) ANon.
1947. RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann, Rpt. 70:21-26.
(16) ——— ,
1946. RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann. Rpt. 69:37-47,
(17) ,
1945. RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann. Rpt. 68:30-35.
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1944, RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann. Rpt. 67:37-43.
(19)
1943. RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann. Rpt. 66:41-51.
(20) ———
1942. RESEARCH AND FARMING. N. C. Agr. Expt. Sta. Ann. Rpt. 65:33-38.
(21)
1946. A SURVEY OF THE RESEARCH STATUS OF THE PEANUT INDUSTRY. Southern
Research Institute.
(22) ——— uae
1948, EL CULTIVO DEL MANI O CACAUETE. Ministerio de Agricultura Y Gane
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(23) ———
1949. CULTUURAANWIJZINGEN VOOR AARDNOTEN. Algemeen Proefstation voor
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(24) ——==
1934, THE PEANUT. Jamaica Agr. Soc. Jour. 38 (10) :639-640.
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1929. CULTIVATION OF GROUNDNUTS. Jamaica Agr. Soc. Jour. 33:307-309.
(26) ———

1920. IMPROVED METHODS OF CULTIVATING THE GROUNDNUT IN SENEGAL,
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1943. SOIL FERTILITY STUDIES WITH PEANUTS. N. C, Agr. Expt. Sta. Bul.
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1946. FERTILIZING PEANUTS IN NORTH CAROLINA: N. C. Agr. Expt. Sta. Bul.
356
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1944. PEANUT PRODUCTION POSSIBILITIES IN SOUTH CAROLINA. S. C. Agr.
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(51) Eyerciro, J. M.
1934, PEANUTS IN THE PHILIPPINES. Philippine Jour. of Agr. 5 (2):47-67.
(52) Ferris, E. B.
1922. PEANUTS. Miss. Agr. Expt. Sta. Bul. 208.
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1946. THE COMPARATIVE EFFECTS OF LIME AND GYPSUM UPON PLANTS GROWN
ON ACID SOILS. Jour. Amer. Soc. Agron. 38:614-623,
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1941, CULTURE AND FERTILIZER STUDIES WITH PEANUTS. Ga. Agr. Expt.
Sta. Bul. 209.
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1941, PEANUT FERTILIZER STUDIES IN GEORGIA. Proc. Assoc. of Southern Agr.
Workers 42:103-104.
(56) Harper, J. N.
1920. MONEY IN PEANUT GROWING. American Fertilizer 52 (3) :67-89,
(57) Harris, H. C.
1949, COPPER DEFICIENCY OF PEANUTS, Proc. of Southern Agr. Workers
46 :164.
, TISDALE, W. B. AND Tissot, A. N.
1946. IMPORTANCE OF EXPERIMENTAL TECHNIQUE IN FERTILIZER, DUSTING AND
CALCIUM EXPERIMENTS WITH FLORIDA RUNNER PEANUTS. Proc. Soil
Sci. Soc. Amer. 11:413-416.
(59) Henprix, W. E., ButLer, C. P. anp Goopman, K. V.
1943. PEANUT PRODUCTION POSSIBILITIES IN GEORGIA. Ga. Agr. Expt. Sta.
Bul. 228.
(60) Hi, A. G.
1947, OIL PLANTS IN EAST AFRICA (1) GROUNDNUTs, East Africa Agr. Jour.
12:140-146.
(61) Jones, B. W.
1911. THE PEANUT PLANT. N, Y. Orange Judd Co. 1885. Rev.
(62) Ker_e, W. D.
1935, PEANUT GROWING. Agr. Gaz. of New South Wales 46:503-508.

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1918. THE PEANUT. Agr. Gaz. of New South Wales 29:137-142, 262-273,
338-343, 429-433, 471-479,
(64) Kerr, J. A.
1946. PEANUT GROWING. Queensland Agr. Jour.
(65) Kittincer, G. B., Sroxes, W. E., CLARK, F. AND WARNER, J. D.
1947, PEANUTS IN FLORIDA. Fla. Agr, Expt. Sta, Bul. 432.
(66) Krauss, F. G.
1917. PEANUTS, HOW TO GROW AND USE THEM. Hawaii Agr. Ext. Bul. 5.
(67) LANGcLey, B. C., REyNotps, E. G. anpD Dunzuap, A. A.
1945. SUMMARY OF PEANUT INVESTIGATIONS IN TEXAS. Texas Agr. Expt. Sta.
Prog. Rpt. 943.
(68) McCLELLanp, C. K.
1944, PEANUT PRODUCTION EXPERIMENTS, 1931-1941. Ark. Agr. Expt. Sta.
Bul. 448.
(69) Mann, H. B.
1935. THE RELATION OF SOIL TREATMENTS TO THE NODULATION OF PEANUTS.
Soil Sci. 40:423-437,

170
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(71)

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(74)

(73)

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(78)

(79)

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(81)

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THE PEANUT—THE UNPREDICTABLE LEGUME

Many, L.

' 1935, EL CACAHUATE BULLETIN. Secretaria de Agricultura Y Formento
(Mexico).

MassizoT, J. A. AND VIDAL, R.

1947, EXPERIMENTATION PRELIMINAIRE DE LA FUMURE DES TERRES A ARA-
CHIDE DE LA REGION DE LOUGA (SENEGAL). L’Agronomie Tropicale
2:247-278.

MEHLIcn, A. AND COLWELL, W. E.

1946. ABSORPTION OF CALCIUM BY PEANUTS FROM KAOLIN AND BENTONITE

AT VARYING LEVELS OF CALCIUM. Soil Sci. 61:369-374.
——-— AND REED, J. F.

1947, THE INFLUENCE OF THE TYPE OF COLLOID AND DEGREE OF CALCIUM
SATURATION ON FRUIT CHARACTERISTICS OF PEANUTS. Proc. Soil Sci.
Soc. Amer. 11:201-205,

MIppLeEton, G, K., CoLwEtt, W. E., Brapy, N. C. AND SCHULTZ, Jr., E. F.

1945. THE BEHAVIOR OF FOUR VARIETIES OF PEANUTS AS AFFECTED BY CALCIUM
AND POTASSIUM VARIABLES. Jour. Amer. Soc. Agron. 37:443-457.

——— AND Farrior, J. W.

1941, RESPONSE OF PEANUT VARIETIES TO DIFFERENT FERTILITY LEVELS. Proc.

Assoc. of Southern Agr. Workers 42:101-102.
Morris, H. D. ;

1941. YIELDS OF PEANUTS AS INFLUENCED BY FERTILIZER. M. S, Thesis,

Agron. Dept., N. C. State College, Raleigh.
——— AND Pierre, W. H.

1947. THE EFFECT OF CALCIUM, PHOSPHORUS AND IRON ON THE TOLERANCE OF
LESPEDEZA TO MANGANESE TOXICITY IN CULTURE SOLUTIONS. Proc.
Soil Sci. Soc. Amer. 12:382-386.

Moser, F.

1942. CALCIUM NUTRITION AT RESPECTIVE PH LEVELS. Proc. Soil Sci. Soc.

Amer. 7:339-344,
Moses, D. AnD SELLscHop, J. P. F.
1946. THE PEANUT IN SOUTH AFRICA. Jour. Dept. Agr. Union S. Africa 12:
569-385.
Murray, G. H.
1935, PEANUTS AS A CROP FOR NEW GUINEA. New Guinea Agr. Gaz. 3:15.
NEtson, W. L.
1948. UNPUBLISHED DATA. N, C. Agr. Expt. Sta.

O'BRIEN, R. E.
1944, FIELD EXPERIMENTS WITH PHOSPHATIC FERTILIZERS. Va. Agr. Expt.
Sta. Bul. 364.
Papen, W.R, |
1940-1943, PEANUTS IN SOUTH CAROLINA. S. C. Agr. Expt. Sta. Mimeogr.
Sheets.

ParuaM, S. A.
1942, PEANUT PRODUCTION IN THE COASTAL PLAIN OF GEORGIA.
Ga. Coastal Plain Expt. Sta. Bul. 34.
Pater, W. F.
1931, FERTILIZING PEANUTS. American Fertilizer, page 36.

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(86) PEEcH, M. AND BRADFIELD, R.
1943, THE EFFECT OF LIME AND MAGNESIA ON THE SOIL POTASSIUM AND ON
THE ABSORPTION OF POTASH BY PLANTS. Soil Sci. 55:37-48.
(87) PIERRE, W. H. anp Bower, C. A.
1943, POTASSIUM ABSORPTION IN PLANTS AS AFFECTED BY CATIONIC RELATION-
sures. Soil Sci. 55:23-36.
(88) Putanp, J. R., IRELAND, C. F. AND REISENAUER, H. M.
1944, THE IMPORTANCE OF BORAX IN LEGUME SEED PRODUCTION IN THE SOUTH.
Soil Sci. 57:75-84,
(89) Potiock, N. A. R.
1934, CULTIVATION OF THE PEANUT. Queensland Agr. Jour. 41:148-164.
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1925. CULTIVATION OF THE PEANUT. Queensland Agr. Jour. 24:108-113.
(91) Prevor, P.
1949, NUTRITION MINERALE DE L’ARACHIDE. Oleagineux 4:69-78.
(92) Quinn, H. G,
1921. THE PEANUT. South Africa Jour. of the Dept. of Agr. 3:160-164.
(93) ReEb, J. F. anp Brapy, N. C.
1948. TIME AND METHOD OF SUPPLYING CALCIUM AS FACTORS AFFECTING
PRODUCTION OF PEANUTS. Jour. Amer. Soc. Agron. 40:980-996.
AND CUMMINGS, R. W.
1948. USE OF SOLUBLE SOURCES OF CALCIUM IN PLANT GROWTH. Soil Sci.
65:103-109.
(95) Rocers, H. T.
1948. LIMING FOR PEANUTS IN RELATION TO EXCHANGEABLE SOIL CALCIUM
AND EFFECT ON YIELD, QUALITY AND UPTAKE OF CALCIUM AND
potassium. Jour. Amer. Soc. Agron. 40:15-31.

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1943-44. VALUE OF LIME FOR PEANUTS. Ala. Agr. Expt. Sta. Ann. Rpt.
54 and 55:9.
(97) ScHMEHL, W. R.
1948. THE NATURE OF CROP RESPONSES TO LIMING AND THE INFLUENCE OF
RATE AND METHOD OF APPLICATION ON THE YIELD AND CHEMICAL
COMPOSITION OF PLANTS. Ph.D. Thesis. Cornell University, Ithaca,
N.Y.
(98) SELLscHoP, J.
1942. GROUNDNUT PRODUCTION. Farming in S. Africa 17:651-654, 670.
(99) Sugar, G. M. AND BatTTeENn, E. T.
1948, MANGANESE DEFICIENCY OF PEANUTS IN VIRGINIA. Proc. Assoc. Southern
Agri. Workers 45:143-148.
(100) SKINNER, J. J., NELson, W. L. anp Cottins, E. R.
1946. POTASH AND LIME REQUIREMENTS OF COTTON GROWN IN ROTATION
WITH PEANUTS. Jour. Amer. Soc. Agron. 38:142-151.
(101) Sommer, A. L. AND Baxter, A.
1942, DIFFERENCES IN GROWTH LIMITATION OF CERTAIN PLANTS BY MAG-
NESIUM AND MINOR ELEMENT DEFICIENCIES. Plant Phys. 17:109-115.
(102) ———, Wear, J. I. anp Baxter, A.
1940. THE RESPONSE TO MAGNESIUM OF SIX DIFFERENT CROPS ON SIXTEEN
ALABAMA SOILS. Proc. Soil Sci. Soc. Amer. 5:205-212,

172 THE PEANUT—THE UNPREDICTABLE LEGUME

(103) STANSEL, R. H.
1935, PEANUT GROWING IN THE GULF COAST PRAIRIE OF TEXAS. Texas
Agr. Expt. Sta. Bul. 503:5-16,
(104) Stoxes, W. E. anp Camp, J. P.
1931. EFFECT OF LANDPLASTER OR GYPSUM ON HAY AND SEED PRODUCTION
OF PEANUT VARIETIES. Fla. Agr. Expt. Sta. Ann. Rpt., page 45.
, LEUKEL, W. A. AND Camp, J. P.
1931. EFFECTS OF POTASH ON YIELD AND QUALITY OF SPANISH PEANUTS.
Fla. Agr. Expt. Sta. Ann. Rpt., page 44.
(106) Stuckey, H. P
1945. WORK WITH PEANUTS AT THE GEORGIA EXPERIMENT STATION. Peanut
Jour. and Nut World 24:25-26.
(107) Sturxigz, D. G., ScHuULTz, Jr., E. F. AND ALBRECHT, H. R.
1943-44, EFFECT OF HIGH RATES OF NITROGEN IN FERTILIZER ON THE YIELD
OF PEANUTS. Ala. Agr. Expt. Sta. Ann. Rpt. 54 and 55:12.
(108) Trmson, S. D.
1930. THE GROUNDNUT. Rhodesia Dept. of Agr. Bul. No. 768.
(109) Vatpivia, M. A.
1936. EL MANI. Revista de Agricultura (Cuba) 18 (4):5-22.
(110) Wa.pron, R. A. ;
1919, THE PEANUT: ITS HISTORY, HISTOLOGY, PHYSIOLOGY AND UTILITY. Cont.
Bot. Lab., Univ. of Pa. I1V:302-338.
(111) Wenuotz,'H., Nicnotson, G. anp WoLk, P. C.
1926. PEANUTS. New South Wales Agr. Gaz. 37:457-462, 512-516, 613-619,
762-768, 842-846.
(112) West, H. O.
1942, PEANUT PRODUCTION. Miss. Agr. Expt. Sta. Bul. 366.
(113) York, Jr., E. T.
1949, CALCIUM-POTASSIUM INTERRELATIONS IN SOILS AND THEIR INFLUENCE
UPON THE YIELD AND CATION CONTENT OF CERTAIN CROPS. Ph.D.
Thesis. Cornell University.

(105)

CHAPTER VI

CULTURAL PRACTICES

D. G. STURKIE AND J. T. WILLIAMSON’

Research work involving some of the cultural practices with peanuts
has been rather limited. Most of the experiment stations have conducted
spacing tests; several have carried time-of-planting and seed-treatment
tests; a few have studied seed preparation, seed types, and disease and
insect control by dusting. However, the data on soil preparation, plant-
ing depths, cultivation, harvesting, curing, picking and perhaps other
phases of this subject are either extremely meager or nonexistent. Station
publications on many of these subjects carry only the authors’ opinions.
The authors of this chapter are in accord with most of these views, and,
where data are not available, they have included such opinions as the
best information obtainable on the subject.

PLANTING
Preparation of the Soil

There are very few data from controlled experiments with different
methods of preparing land for peanuts. However, there is practically
unanimous agreement among all research workers and extension agrono-
mists that the land should be thoroughly and completely prepared before
planting. Land is prepared for peanuts in much the same way as for
cotton. Plowing is done early when there is no winter cover crop on the
land. It is difficult to prepare land properly for peanuts if a large
growth of residue from the preceding crop is turned under just prior
to planting. For this reason plowing in the late fall or early winter is
practiced frequently in order to permit complete decomposition of
residues before time for planting. When a winter cover crop such as

1D. G. Sturkie and J. T. Williamson are agronomists, Alabama Agricultural Experiment
Station.

173

174 THE PEANUT—THE UNPREDICTABLE LEGUME

lupine or vetch is used, it is plowed under at least 30 days beforespeanuts
are planted. In case weeds come up on the field, the land is disked to
eradicate the weeds. The land is harrowed and dragged immediately
before planting.

There are no data on depth of preparing the soil. Apparently, ex-
cessively deep preparation is to be avoided. Most lands should be pre-
pared to a depth of from 5 to 7 inches.

Fertilizer Applications

Although the subject of peanut fertilization has already been dis-
cussed in Chapter V, brief comments are included here.

Many research workers have found that peanuts following a crop that
was well fertilized with mineral fertilizers do not give increased yields
from direct applications. However, it is still a general practice to apply
fertilizers in the drill at planting and in some cases as top-dressing
materials later in the season.

Fertilizers that are used in the drill are applied either to the side and
slightly below the seed or well mixed with the soil so that they will not
come in contact with the seed and thus reduce the stand. Many research
workers recommend that fertilizers be applied 1 to 2 weeks ahead of
planting.

In some sections it has recently become a common practice to apply
fertilizers on the row just as the plants are emerging. This is especially
true of potash materials. When this practice is followed the fertilizer is
applied when the plants are dry in order to avoid burning. Cultivation
with a weeder or rotary hoe should follow immediately so as to remove
any fertilizer that may have come in contact with the plants. Batten (2)
recommends that only concentrated potash salts be used in the fertilizer
application made before planting because the use of a greater volume of
the low-grade salts required to obtain the amount of potash needed often
causes poor germination.

Use of gypsum on the foliage of large-type peanuts at blooming
time has given outstanding increases in yields in North Carolina and Vir-
ginia. Experiments in other States have indicated little or no benefit
from this practice when Spanish or the small runner-type peanut is
grown. Studies have shown that gypsum is most beneficial if applied
when the peanuts begin blooming. Gypsum has usually been dusted on
the foliage by hand, but the use of machines for application is increasing.

Where limestone is applied inthe drill before planting, it should be
used as a separate treatment from the fertilizers that are applied at this

CULTURAL PRACTICES 175

time. It is believed, however, that the best practice is to plant peanuts on
land that has been adequately limed by previous broadcast applications.

Time of Planting

Throughout the greater part of the commercial peanut area, planting
of the main crop is done between April 10 and May 10. Peanuts are
planted from early March in parts of Texas and Florida to as late as
June 15 in Virginia and North Carolina. The young peanut plant is
capable of withstanding considerable cold. Therefore, peanuts may be
planted earlier than cotton. The recommendations made by most agrono-
mists are for planting at a reasonably early date. The best planting date is

Table 1—ANNUAL AND AVERAGE YIELDS OF SPANISH PEANUTS PLANTED AT DIF-
FERENT DaTEs, LAUDERDALE, Mississiprt, 1940-1941

Yield per acre
Date of planting
1940 1941 Average
Pounds Pounds Pounds
April Se. ciidseais pasciiee tanks ® 1,550 920 1,335
May 15% a sccis edie Sons oe ee teehee 1,200 860 1,030
JMO TS oe woes Mees Aes SSEN Se He 1,356 610 983

® All plots received 400 pounds per acre of 0-8-4 with basic slag as a source of phosphorus; peanuts
planted in 30-inch rows, 6 to 8 inches apart in the drill.

probably about 2 weeks after the average date of the last killing frost.
Results of time-of-planting experiments show that farmers could very
probably increase their yields by planting earlier than customary. In the
Gulf Coast region, a fair yield may be expected from Spanish peanuts
planted as late as July 1. Runner-peanut yields decline very rapidly as the
date of planting is delayed.

Results from experiments on dates of planting in Mississippi (18) are
given in table 1. These results show that yields from peanuts planted
early are definitely higher than from peanuts planted at later dates.

Peanuts planted in April, May and June 1940-1943 at Rocky Mount,
North Carolina (6) produced average yields of 1,215 pounds, 1,151
pounds and 710 pounds of nuts per acre, respectively. An exception to
the above trend was noted in 1944 when slightly higher yields were
obtained from the May than from the April planting.

Results of 10-year experiments at Tifton, Georgia (8), as shown in
table 2, also indicate an advantage of early planting of both Spanish and
runner peanuts.

176 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 2.—AVERAGE YIELDS OF UNFERTILIZED PEANUTS PLANTED AT DIFFERENT
DaTEs, GEORGIA COASTAL PLAINS EXPERIMENT STATION, TIFTON, 1934-1943,

Yield of unshelled nuts per acre
Planting date
Spanish North Carolina

Runner
Pounds Pounds
March d Sistnioe aaiae ceiee dara aeen Gen 1,388» 1,925¢
AUDEN 45) O iastkioaannalia, Redeus warner panes elaivare 1,338 1,860
April 15.5 comets Ge wenas weer eae ne aaias 1,335 1,804
May Mee eo sreccus-nicacncanrsarinaient tera Suse eee ae 1,244 1,590
May lS sdvaavene dana vacuinde ods sobs svieee on 1,062 1,313
Jims cz secon ss ees kee kee ee GE eA EE SS 645 866

® No fertilizer used. Tests followed a general rotation of field crops.
b 8-year average, no data for 1934 and 1935.
¢ 9-year average, no data on March 15 planting in 1934 or on April 15 planting in 1943.

Yields from experiments conducted with Spanish peanuts at various
Alabama locations are given in table 3. Except at Fairhope, where early
plantings were damaged by rodents, these results also show a very defi-
nite advantage for early seeding. Planting at or about the last killing-
frost date resulted in a good yield of peanuts. Slightly higher yields were
obtained by delaying the planting 2 weeks after the last killing frost.
Delaying the planting an additional 2 weeks, however, resulted in marked
reduction in the yield.

In a date-of-planting experiment with runner peanuts at Auburn,

Table 3.—AVERAGE YIELDS OF SPANISH PEANUTS PLANTED AT DIFFERENT DATES
AT Various LocaTIONS IN ALABAMA, 1943-1946

Average yields per acre®
Location Years
Ist planting>| 2nd planting| 3rd planting
Number Pounds Pounds Pounds
Pai rhope acacia swe e noise otek 2 1,657 2,264 2,109
Prattville: cisco cis states ccs too. tecie since 3 1,096 981 840
AUBUEM s 55.00 i es eteld des ee aes 4 1,016 1,154 983
Alexandriaws..sseeesiews aces 2 1,706 1,345 1,091
Crossvill@s sisociig eegcs eneg ss wae 4 1,699 1,729 1,562
Belle Mina................4. 1 1,940 1,941 1,781
AVETA SES ha ioisen dada Greer Ranbers 1,426 1,477 1,305

8 Vields are average of four plots; planting rate per acre 90 pounds of hand-shelled, and 60, 90 and
135 pounds of unshelled seed, respectively.

b Plantings made at approximately 15-day intervals, first planting at about the average date of last
killing frost at each location and varied from March 9 at Fairhope to April 17 at Crossville.

CULTURAL PRACTICES 177

Table 4.—Two-YEAR AVERAGE YIELDS OF RUNNER PEANUTS PLANTED ON NORFOLK
Sanpy Loam aT DIFFERENT Dates, AUBURN, ALABAMA, 1945-19468

Date of planting Yield per acre
Pounds
March 15 1,064
April 5 1,268
April 25 994

® 300 pounds per acre of 0-14-10 applied before planting; rows 30 inches apart; 90 pounds of unshelled
seed planted per acre.
Alabama, the highest yield was obtained from the April 5 planting. The
results are reported in table 4.

Runner peanuts were planted at 10-day intervals from April 5 to June

15, 1939-1946, inclusive, in a test at Prattville, Alabama. The average
yields for all years are shown in table 5. Highest yields were obtained
from planting on April 5. For some unexplainable reason, peanuts planted
on April 15 produced less yield than those planted on either April 5 or
25 in 6 of the 8 years that the experiment was conducted.

Method of Planting

Peanuts are usually planted in a shallow furrow and are covered
to a depth of 114 to 3 inches on light soils and 1 to 2 inches on heavier
soils. Under dry conditions, still deeper covering is recommended. After
the seed are covered, the top of the seedbed is slightly below ground
level. This allows early cultivation with a weeder or rotary hoe without
danger of injury to young plants.

Table 5.—AVERAGE YIELD OF RUNNER PEANUTS PLANTED AT DIFFERENT DATES,
PRATTVILLE EXPERIMENT FIELD, PRATTVILLE, ALABAMA, 1939-1946

Yield marketable
Daie of planting peanuts per acre
Pounds
April Svinccc cue neue es Healt g Geek ahd ee eee eee ea 1,570
April (5 vcoss cocrdesomatacdoan tae cee eee tet eueT ea Se 1,417
PAPE 2 Sane oh ice ernie BARA ANE era ara te ar pahie asa ens anraganes ala vee ein 1,498
Maly Orie tore De hen Sree Poa eanas Nala « Sek wes ae ok eta eal 1,346
May 17. ceecsver ses dg Goth shiaiik ¥Quvte Hien abre) ges taeera te RUSH pe 1,260
May 25 ic ca sence waar eb @iiba BW Bawa Goins ies ecntata oe ake ene Gra 1,166
JONES iso maieuenam aad ode p mnie Kom A eae Bo dee TOS OY ee Oe 1,051>
PUT Die oj Snors hpi nd wisi S Share ae bunceabyg se age ahendep aeeeranacane o Niepene ass 742»

® Rows 36 inches apart; hills spaced uniformly each year but varied from 8 to 12 inches from year to
year. No fertilizers applied to peanuts.
b 7-year average; not jncluded in 1939.

178 THE PEANUT—THE UNPREDICTABLE LEGUME

In some localities the land is bedded before planting. At the time of
planting, the bed is opened with a small shovel or bull-tongue scooter
large enough to clean the beds and deep enough to level the top.

After planting, the row should be slightly below or about even with
the middle and with a slight ridge in between. If the land is freshly
broken, usually no bed is formed. In this case, planting is made in a
small open furrow and the seed are covered sufficiently to level the surface
of the furrow slightly below the middle surface. Planting preparation in
any case should leave the ground in proper shape for the use of weeders
or rotary hoes, or for barring-off rows.

Spacing of Peanuts

Spacing tests to determine distances between rows and spacing of
hills in the row have been conducted by most of the experiment stations

Table 6.—AVERAGE YIELDS OF RUNNER PEANUTS SPACED AT DIFFERENT DISTANCES
IN THE Row, WIREGRASS SUBSTATION, HEADLAND, ALABAMA, 1936-19438

Spacing
Average yields per acre
Between rows Between hills
Inches Inches Pounds
42 7 1,666
42 14 1,594
42 21 1,377
42 28 1,326

® 400 pounds per acre 0-8-4 used before planting; 200 pounds per acre of gypsum applied as a top
dressing when blooming began.

in the peanut-growing States. These tests have been made with both
bunch- and runner-type peanuts. In general, the results show that narrow
rows and thick spacing in the row produces the largest yields. When
plants are spaced wide in the drill some of the larger types of peanuts
produce nuts that are known as Jumbos.

Alabama Agricultural Experiment Station Results. Reported in table
6 are average yields from a spacing test of runner peanuts conducted for
8 years, 1936-1943, at the Wiregrass Substation, Headland. Highest
yields were obtained from plants spaced 7 inches apart in the row.

From an experiment conducted at Auburn, Alabama, 1918-1922, in-
clusive, Funchess and Tisdale (5) found that Spanish peanuts must be
planted thick for large yields. They obtained extreme yields of 1,785
pounds of nuts per acre from 4-inch spacing in 18-inch rows and 813

CULTURAL PRACTICES 179

pounds from 12-inch hills in 36-inch rows. Average results for the 5-year
period of the test are given in table 7.

Arkansas Agricultural Experiment Station Results. McClelland (10)
reported that tests with rows as narrow as 12 to 18 inches apart were
conducted in 1919. However, these tests were not continued because of
the difficulties encountered in cultivating these narrow rows. The yields
of peanuts and of hay were larger than when the peanuts were planted
in wider rows.

Table 7.—AVERAGE YIELDS OF SPANISH PEANUTS WHEN PLANTED AT DIFFERENT
Spacincs, Main Station, AUBURN, ALABAMA, 1918-1922

Row width Spacing in rows Average yield nuts per acre
Inches Inches Pounds
18 4 1,785
24 4 1,581
30 4 1,308
36 4 1,299
18 8 1,323°
24 8 1,170
30 8 1,146
36 8 813
18 12 1,437
24 12 1,158
30 12 1,002
36 12 813

Spacing experiments conducted during the period 1925-1930, in-
clusive, also were reported. The average results are given in table 8.
Spanish and Valencia varieties were used in these tests. Higher yields
of both nuts and hay were obtained from the Spanish variety when
grown in 30-inch rows and spaced 6, 8 or 9 inches apart in the drill. The
Valencia variety produced highest yield in either 30- or 36-inch rows with
6, 8 or 9 inches between the hills.

In a later test (11), 1931-1941, highest yields of the Valencia variety
were obtained when spaced 8 inches apart in 30-inch rows. The Spanish
strains produced best from a 36-by-8 inch spacing. There was little differ-
ence in the yield of either variety between rows of 30 and 36 inches.
Spacings of less than 8 inches in the row were not included in the tests.
Highest yields of hay from both varieties were obtained from 30-by-8
inch spacing. Average yields of nuts and hay from various spacings for
1931-1934 and for a 9-year average between 1931 and 1941 are given in

table 9.
Florida Agricultural Experiment Station Results. In 1928 and 1929

180 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 8—AVERAGE YIELD OF PEANUTS AT DIFFERENT SPACINGS, ARKANSAS
AGRICULTURAL EXPERIMENT STATION, FAYETTEVILLE, 1925-19302

Yields per acre
Width of rows Spacing in row
Peanuts Hay
Inches Inches Pounds Pounds
Spanish
BO ecar PB Gg weds) ayarituadeeast duds Suites 6-8-9 1,190 4,526
3 Oi suactieuguaeudduecabosted W aaviackastees 10-12 1,027 4,151
BOE stated ceo aie tere treatin weak 15-16 919 3,197
8G aintiin tues hog wud aaah woe 6-8-9 987 3,797
30s diss Gpaease wee ae Ee rae 10-12 925 3,356
JOunened wen Yaw es cote eS 15-16 750 2,928
Valencia
OOS cas tinigaty caves dea ainas 6-8-9 525 3,000
BO ele Sig Rion Danes leant ee 10-12 509 2,738
BOs ecb are st acne -anaeed nea 15-16 371 2,071
BO its oS ase gee xchat bacaedys 6-8-9 542 2,708
DOs siieigauavk aecedag es ewee 10-12 369 2,170
SO sacs cymexen eyes See nae 15-16 292 1,771

® No results reported in 1927,

Table 9.—AVERAGE ACRE YIELDS OF PEANUTS AND PEANUT Hay, ARKANSAS
AGRICULTURAL EXPERIMENT STATION, FAYETTEVILLE, 1931-1934 AND 1937-19412,

Average acre yield Average acre yield
Variety and Spacings 1931-34 1931-1934 and 1937-1941
Nuts Hay Nuts Hay
Inches Pounds Tons Pounds Tons
Valencia? re
$050 Be cot uaale veel ade ey 1,494 2.34 1,316 2.03
BOR Drie secu al aromas 1,442 2.25 1,249 1.98
36%: 16's ewslee nyse a aie ils ge 1,284 2.08 —_ —_
30 Xo eatin oe Wek sa om zeae ee 1,394 2.58 1,395 2.25
30X12 sce ves cas 24 tae eh wae eS 1,286 2.54 1,260 2.19
90.2 1G. dn ctareecere sets 1,230 2.28 —_— —
White Spanish¢
OX 8 ness amas Dogan a RE | 2,520 2.98 2,160 2.60
36 X12 cca eecyuge peas 2,412 2.98 1,873 2.39
BG 16 ois utescaw ng ng Weis ens eA 2,277 2.94 _— _
30 X85 cacesis ta nicaevesey ea 2,425 3.20 2,101 2.75
BOR VD ioe sisraracn newness a Yoo ties t 2,331 3.17 2,037 2.69
BOE 1G esses socwiace Soe. ahaeeas eas 2,213 3.31 —_ —

® Crop failures in 1935 and 1936 not included.
b Tennessee Red substituted for Valencia in 1941,
¢ Improved Spanish used in tests, 1937-1940.

. CULTURAL PRACTICES 181

Table 10.—AVERAGE YIELDS OF FLORIDA RUNNER AND SPANISH PEANUTS SPACED AT
DIFFERENT DISTANCES IN 30-INCH Rows on NorFOLK SAND, EXPERIMENT STATION
Farm, GAINESVILLE, FLoripA, 1928-1929

LY
Spacing of Yield of nuts per
Variety plants in acre; average
drill 1928 and 1929

Pounds Pounds

Florida Runner............... 00000 cece 6 1,282
12 958

24 912

Spal is hin; vxiacy anergy nae ese 3 990
6 7176

9 631

the station (7) conducted spacing tests with both runner and Spanish
peanuts. The average results for the 2 years are reported in table 10.
Highest yields were obtained from runners spaced 6 inches and Spanish
spaced 3 inches in the drill.

Georgia Coastal Plain Station Results. Average results of spacing
tests conducted 1930-1936 (14) are reported in table 11. The tests with
Spanish peanuts were conducted at Tifton. Highest yields were obtained
from 6-inch hills with rows 18 inches apart. It is reported, however, that
this width row is harder to cultivate than wider rows and attention is
called to the fact that such narrow rows and spacing require larger
quantities of seed. Rows spaced 24 to 30 inches apart with hills 6 inches
apart are believed to be the most practical for the Spanish variety.

Table 11.—AVERAGE YIELDS OF SPANISH PEANUTS IN SPACING TEST AT THE GEORGIA
CoasTAL PLAIN EXPERIMENT STATION, TIFTON, 1930-1936

Spacing Yield of unshelled nuts
per acre
Between row In row

Inches Inches | Pounds
36 3 1,393
36 6 1,360
36 12 1,212
36 18 1,131
36 24 932

6 6 1,509

18 6 1,561
24 6 1,503
30 6 1,356
36 6 1,139

182 THE PEANUT—THE UNPREDICTABLE LEGUME Z

North Carolina Agricultural Experiment Station Results. The results
from spacing tests with various varieties of peanuts conducted at the
Rocky Mount Station (6) are reported in tables 12 to 15, inclusive. Data
were obtained on both Virginia Bunch and Jumbo Runner peanuts
planted in 3-foot rows in hills 4, 8, 12 and 16 inches apart with one and
two plants pec hill. Highest yields were obtained from 1929-1931 (table
12) where the Virginia Bunch variety was spaced 4 inches apart in the

Table 12.—RESULTS OF PEANUT-SPACING TESTS, UPPER COASTAL PLAIN STATION,
Rocky Mount, NorTH CAROLina, 1929-1931

V'rginia Bunch

4 1 1,428 11.2 31.5 5A 65.5 150 450 217 846
8 1 1,227 15.1 42.2 4B 63.1 168 522 214 706
12 1 1,163 15.2 39.3 5B 61.5 159 451 152 619
16 1 1,114 14.4 36.1 5B 61.9 150 400 149 598
8 2 1,390 15.4 40.1 4B 62.9 204 555 234 791
12 2 1,324 16.4 39.5 5B 62.2 206 526 184 734
16 2 1,248 14.8 38.2 5B 61.7 173 480 185 688
Jumbo Runner
4 1 1,695 29.9 46.5 2B 63.0 487 815 333 998
8 1 1,700 32.3 49.4 2B 62.3 530 858 282 988
12 1 1,793 36.4 53.6 1B 61.8 621 986 351 |1,007
16 iL 1,610 | 38.8 55.5 1B 64.0 601 923 310 954
8 2 1,832 36.2 49.4 1B 61.5 633 901 353 {1,016
12 2 1,902 32.3 53.0 2B 63.5 593 |1,053 369 11,144
16 2 1, 848 32.7 $1.3 2B 64.4 597 |1,011 368 = |1,138

8 Rows 3 feet apart.

drill with one plant per hill. Two plants per hill with hills either 8 inches
or 12 inches apart produced only slightly less peanuts than the 4-inch
spacing of this variety. Jumbo Runners produced highest yields when
spaced 12 inches apart in the drill with two plants per hill.

In other tests conducted in 1929-1931 and 1936-37 at the same
location (table 13), approximately equal results were obtained from
spacings of two plants per hill 8 inches apart, one plant per hill 4 inches
apart, and two plants per hill spaced 12 inches apart. Wider spacing gave
much lower yields.

CULTURAL PRACTICES 183

Table 13,—RESULTS or PEANUT SpacinG TESTS, UPPER COASTAL PLAIN STATION»
Rocky Mount, NortH CaRro.ina®

Hills picks medium

9 Conducted during seasons of 1929-1931 and 1936-1937.

In tests at Rocky Mount in 1943 and 1944 (table 14) best yields were
produced from thick spacing of both North Carolina 31 and Spanish 2B
varieties. Both varieties yielded most when spaced 4 inches apart in the
row with rows 18 inches wide. In a test conducted in 1947 (table 15), the
highest yields from no potash were obtained from hills 4.5 inches apart
in rows 18 inches wide. In the case of the potash treatment spacing 4.5
and 9 inches between hills in 18-inch rows and 4.5 inches between hills in
27-inch rows produced approximately the same yields.

South Carolina Agricultural Experiment Station Results. Spacing-
test results at the Pee Dee Station, Florence (3) showed that the highest
yields were produced where Spanish peanuts were spaced very close in
the row, the best yields of nuts being obtained from plants spaced 3 inches
apart in 2.5-foot rows. Table 16 records the average results obtained
from nuts and forage.

Table 14.—AVERAGE YIELDS OF PEANUTS AT DIFFERENT SPACINGS IN TESTS AT
Upper CoAsTAL PLAIN STATION, Rocky Mount, NortuH Caro.ina, 1943 anp 1944

Average yields per acre, variety and row width
Distance
between North Carolina 31 Spanish 2B
Hills
18” 24" 30” 36” 18" 24” 30" 36"
Inches Pounds | Pounds | Pounds | Pounds | Pounds | Pounds | Pounds | Pounds
4 1,974 1,876 1,470 1,358 1,862 1,610 1,106 1,330
8 1,732 1,616 1,377 1,435 1,519 1,439 1,175 1,320
12 1,503 1,506 1,280 1,160 1,339 1,328 1,213 1,093
16 1,353 1,351 1,288 1,069 1,162 920 924 | 998

184

Table 15,—ReEsuLts or PEANUT SPACING Tests, UpreR CoastaL PLAIN STATION,
Rocky Mount, Norru Carowina, 1947

THE PEANUT—THE UNPREDICTABLE LEGUME

Average yields per acre from different spacings with and
Distance without potash
between
Hills No potash With potash
18 in. 27 in. 36 in. 18 in. 27 in. 36 in.
Inches Pounds | Pounds | Pounds | Pounds | Pounds | Pounds
49s ee ee eS 2,805 2,305 1,557 2,985 3,040 2,305
DO yeseee tc ui Bite ats 2,399 2,218 1,558 3,135 2,506 1,745
LSS 's secs tue dint 2,311 2,205 1,481 2,910 2,495 1,943

L. S. D. (05) Potash-levels, 196 pounds; row width, 306 pounds; row spacings, 189 pounds.

Texas Agricultural Experiment Station Results. Spacing tests with
peanuts have been reported from several Texas substations. At Substa-
tion No. 11, Nacogdoches (12), Spanish peanuts were planted for
normal stand in 18- and 36-inch rows, 1914-1916. The average yields for
the 3-year period were 30 bushels of nuts and 0.59 tons of hay per acre
in the 36-inch rows and 32 bushels of nuts and 0.54 tons of hay per acre
in the 18-inch rows.

Average yields from experiments at Substation No. 8, Lubbock (12),
conducted 1919-1923 and 1925, are given in table 17. Spanish peanuts
were used in these tests. Highest yields of both nuts and forage were
obtained from the 6-inch spacing between hills.

Tuble 16.—AVERAGE YIELDS OF SPANISH PEANUTS SPACED AT DIFFERENT INTERVALS,
PEE DEE EXPERIMENT STATION, FLORENCE, SOUTH CaROLina, 1917-19194

Row Spacing in Yield of peanuts Yield of hay

width rows per acre per acre

Feet Inches Pounds Pounds
DUB sik Skea Ga Saas Bhan aio dey, 3 850 2,023
6 713 2,057

9 590 1,610
12 573 1,693

15 595 1,560

Siseecee ane satiate iG aweeale ote 3 763 1,830
6 653 1,657

9 653 1,700

12 570 1,607

15 477 1,420

2800 pounds per acre of 2-8-3 fertilizer used 1917 and 1918; 470 pounds per acre used in 1919,
Shelled peanuts used in 1917 and 1918, and unshelled nuts used 1n 1919,

CULTURAL PRACTICES 185

Table 17.—AVERAGE YIELDS PER ACRE OF NUTS AND FORAGE FROM SPANISH PEANUTS
PLANTED ON LAKE CHARLES CLAY AND CLay LoAM AT DIFFERENT SPACINGS,
TEXAS SUBSTATION No. 8, LuBBocK, TExas, 1919-1923 AND 1925%

6-year average
Spacing between plants»
Nuts Forage

Inches Bushels Tons

Gia asia eal ee wate arena edeign pid Sea ieme S 49.6 1.78
D seeaiczirieenist tor pha dus antealind G, dex gebesm Reams toes ethan 45.4 1.62
M2 ist sve ck iascae avails ane ecsidl ak sunroce alate onsale ahah 42.0 1.51
1D. Si acca eee cee de GA GND ane eee are 39.8 1.20
Sinise oatoseauon Geom ak amare i eiees ae ahandes 35.1 1.34

® No yield shown for 1924,
b 36-inch rows.

Spacing experiments were conducted at Substation No. 3 at Angleton
(16). Due to the fact that the spacings of plants in the row were variable
from year to year, only the data from 1916-1918 are reported in table 18.
The results for other years are in keeping with these data in that the nar-
row spacings practically always gave the highest yields per acre. Highest
yields were obtained from the 6-inch spacing.

Virginia Agricultural Experiment Station Results (2). Recom-
mends spacing Jumbo and Virginia Runner varieties 10 to 16 inches
apart in the row with rows 30 to 40 inches apart; and Spanish from
6 to 12 inches apart in the drill with rows 24 to 30 inches apart.

Miller (13) found that increased vine growth was obtained where
runner peanuts were dusted to control diseases and insects. Experiments
were conducted to determine the spacing between rows that would favor
the highest yields of peanuts receiving three or four applications of sul-
fur dust. It was found that the highest yield of good quality nuts was
obtained from dusted plants that were grown in rows farther apart than

Table 18.—AVERAGE YIELDS PER ACRE OF SPANISH PEANUTS FROM DIFFERENT
SPACINGS OF PLANTS, TEXAS SuBSTATION No. 3, ANGLETON, TEXAS, 1916-1918

Spacing of plants in row Average yield of peanuts

Inches Pounds

2,754
2;470
2,493
2.473
1,840

186 THE PEANUT—THE UNPREDICTABLE LEGUME

customary. Specific spacing recommendations are not made, but it is
suggested that rows be spaced at least 32 to 38 inches apart for runners
with plants spaced several inches wider than the customary spacing in
the row.

A very large percentage of the spacing experiments with peanuts
have been conducted with the Spanish variety. They show that this
variety yields most in rows 18 to 24 inches apart with plants 4 to 6 inches
apart in the row. Tests in which the larger bunch types or the runner
types were used show that they should be planted in 30-inch rows with
plants 6 to 8 inches in the row.

Seed per Acre

Poor stands due to planting an insufficient quantity of seed are one
of the causes of low yields of peanuts. It is not possible to recommend
accurately the quantity of peanuts needed per acre because of the extreme
variations found in the size of seed even within a variety. Parham (14)
made counts and calculated the approximate seeding rate shown in table
19.

Killinger et al. (7) suggest that 30 to 35 pounds of shelled or 50
pounds of runner seed in the hull are sufficient for planting an acre in
30- to 36-inch rows where peanuts are to be 6 to 8 inches apart in the
drill. They suggest 50 pounds of shelled Spanish peanuts for spacings of
3 to 5 inches apart in 24-inch rows.

Sturkie (17) recommends 50 to 75 pounds of shelled seed per acre for

Table 19 —APPROXIMATE QUANTITIES OF PEANUTS NEEDED TO PLANT ONE ACRE AT
DIFFERENT SPACINGS

Amount of seed needed at five different row widths
Hill
Variety spac- | 18-inch row 24-inch row 30-inch row 36-inch row 42-inch row
ing
Shelled| Un- |Shelled| Un- |Shelled| Un- |Shelled| Un- |Shelled| Un-
shelled shelled shelled shelled Shelled
Inches| Pounds| Pounds| Pounds} Pounds|Pounds|Pounds|Pounds|Pounds|Pounds| Pounds
Spanish....... 3 89 215 67 161 55 129 45 108 _ —_
Spanish....... 6 45 107 34 81 27 65 22 54 — =
Spanish....... 8 34 81 25 61 20 48 17 40 —_ ae
Spanish....... 10 27 65 20 48 16 39 13 32 —_— =
Spanish....... 12 22 54 17 40 13 . 32 11 27 —_ fare
N.C. Runner. . 6 _ = 47 118 37 94 31 78 27 67
N.C. Runner. . 8 _ —_ 35 88 28 71 23 59 20 50
N.C. Runner..} 10 —_— _ 28 71 22 57 19 47 16 40
N.C, Runner..} 12 = oe 23 59 19 47 16 39 13 34
N.C. Runner..| 14 —_ —_ 20 50 16 34 13 33 11 29

CULTURAL PRACTICES 187

spacings of 3 to 4 inches in 2-foot rows. In 3-foot rows, 25 to 40 pounds
of seed are needed for spacings of 6 to 8 inches between plants.

The Alabama Station conducted 23 tests at eight locations, 1943-
1946, inclusive, and obtained practically perfect stands from planting 90
pounds of unshelled Spanish seed. Poor germination, covering either too
shallow or too deep, low vitality, and other factors affect emergence and
early growth of peanuts. It is usually necessary to plant 20 to 25 percent
more peanuts than the theoretical quantity necessary to obtain a stand.

SEED PREPARATION AND TREATMENT

High-yielding strains and varieties of peanuts are being developed.
Stock from these improved strains should be obtained by the grower,
multiplied and used for planting. When the crop is mature, peanuts for
seed should be harvested during dry weather and placed in small stacks
around poles as described in another section of this chapter. They should
be left in the stack for about 4 to 6 weeks before picking. After picking,
the seed peanuts should be either sacked or stored in bulk in a dry place
where there is free circulation of air. Peanuts should not be stored in
sufficient bulk to cause heating. When they are spread rather than piled
in one large heap, there is less danger of heating. Stored peanuts should
be protected from mice, rats, insects and other pests.

Shelled vs. Unshelled Seed

Both shelled and unshelled nuts are used for planting. The large-
seeded varieties are practically always shelled before planting, but some
growers plant the Spanish variety without shelling.

Tests by the Alabama Station show that unshelled Spanish peanuts
planted at heavy rates produced good stands and satisfactory yields
as compared with an equal quantity of seed that were shelled and planted.
Results of these tests are given in table 20. In the tests 90 pounds of
seed per acre planted either in the hull or after shelling produced a stand
of plants averaging approximately 4 inches between hills. In 14 of the
23 tests, 60 pounds of unshelled seed per acre produced a stand averaging
5.15 inches between hills. It may be seen that unshelled peanuts gave a
slightly decreased stand and yield when planted late. These decreases are
believed to be due to a shortage of soil moisture at the time of the late
planting, which reduced germination of the unshelled seed.

In other tests conducted at Auburn in 1943 and 1944 (19) in which
low-vitality Spanish seed were used, low emergence was obtained from un-

188 THE PEANUT—THE UNPREDICTABLE LEGUME

Table 20.—AVERAGE NUMBER oF PLANTS PER 100 FEET oF Row AND AVERAGE
YIELD OF SPANISH PEANUTS WHEN PLANTED AT DIFFERENT DarTEs, USING
DIFFERENT RaTES AND CONDITIONS OF SEED; Various LocaTIONS, ALABAMA,

1943-1946
Weight of seed | Conditions of Average number of plants per 100 feet of row
in shell— seed
pounds when , First Second Third Average all
per acre planted planting planting planting dates of
planting
90 Hand shelled 298 351 320 323
90 Unshelled 319 319 277 306
135 Unshelled 422 406 364 397
Average by
plantings 346 359 320 342
Average yield in pounds per acre®
90 Hand shelled 1,406 1,513 1,236 1,385
90 Unshelled 1,473 1,471 1,291 1,412
135 Unshelled 1,425 1,405 1,275 1,368
Average by
plantings 1,435 1,463 1,267 1,388

® First planting was about the date of the last killing frost and varied from March 9 1n extreme
southern Alabama to April 17 in northern Alabama. The other plantings were made at 2-week intervals
following the first planting.

b Average of 23 tests at the eight following locations: Fairhope, Brewton, Headland, Prattville,
Auburn, Alexandria, Crossville and Belle Mina.

° Yield data from 14 tests at six following locations: Fairhope, Prattville, Auburn, Alexandria, Cross-
ville and Belle Mina.

shelled, hand-shelled and machine-shelled seed. In these tests unshelled
seed germinated only 58 percent and hand-shelled seed 72 percent.

In tests by the Georgia Coastal Plain Experiment Station (8), No.
1 hand-shelled Spanish peanut seed germinated better and yielded more
nuts than either unshelled or small shriveled seed—often called “pegs.”
Emergence results from various seed types are presented in table 21.

Table 21.—F1ELD EMERGENCE OF SPANISH PEANUT SEED TYPES, GEORGIA COASTAL
PLAIN EXPERIMENT STATION, TIFTON, GEorGIA, 1942-1944

Sced typ2
Year No. 1 No. 1
hand machine | Unshelled | Medium Small

shelled shelled pegs pegs

Percent Percent Percent Percent Percent
NAD asi aces sdess 5958 Ne ap ye 87 83 64 66 53
1943 ose wena ok wae wk a 76 62 39 51 40
DAE ora cing pple aoa 88 82 61 83 78

CULTURAL PRACTICES 189
Method and Time of Shelling

One of the first studies on time of shelling peanuts was by Beattie
and others (3). Hand-shelled seed of seven varieties of peanuts—
Jumbo, Virginia Bunch, Virginia Runner, African, Valencia, Spanish and
Improved Spanish were planted at the Pee Dee Station, Florence, South
Carolina, 1922-1924. Shelling was done about February 10, March 10,
April 10 and May 10. All seed were planted soon after the last shelling.
All peanuts were spaced 6 inches apart in rows 32 inches apart. The
data in table 22 show that there was no consistent decrease in the germin-

Table 22, AVERAGE GERMINATION OF SEVEN VARIETIES OF PEANUTS FROM SEED
SHELLED IN DiFrERENT Monrus, 1922-1924

Rate of germination*
Variety

February March April May

shelling shelling shelling shelling

Percent Percent Percent |, Percent
JUMbDO pas 2ecwrne Bae GiS4 hh oe eas 78 82 77 78
Virginia Bunch.................. 87 72 87 79
Virginia Runner................. 86 75 85 86
Alabama Runner (African)........ 86 78 79 83
Valencia...... Gi cde ahi nak lant is 89 76 75 87
SPAanishsyeswecn ae ew eaa ae Meee 92 87 87 93
Improved Spanish 92 79 81 85

® Fractional percentages omitted.

ation of peanuts from seed shelled 3 months before planting time and
that shelled shortly before planting. Seed shelled in December and Janu-
ary of 1923 and 1924 also germinated as well as seed shelled immediately
before planting.

Wilson (19) at the Alabama Station found that hand-shelled runner
peanuts gave the same percentage germination whether shelled 6 weeks,
3 weeks or 1 day before planting, and gave practically the same per-
centage when shelled 9 weeks before planting. Similar results were ob-
tained by the Georgia Coastal Plain Experiment Station (9). Seed
shelled in January and planted in April produced stands equally as good
as those shelled and planted in April.

Prior to World War II nearly all peanuts for planting were shelled
by hand. Some are still hand-shelled, but this method of preparing seed
for planting is rapidly decreasing. Labor shortage, labor cost, and the
fact that hand shelling is a tedious, monotonous operation account for the
decline of handshelling.

190 THE PEANUT—THE UNPREDICTABLE LEGUME

Machine shelling often breaks the skin on a large percentage of nuts
and sometimes damages the seed by crushing or breaking the nuts in
half. This is especially true if ungraded peanuts of uneven sizes are being
shelled. It is also true with graded nuts, if the machine is not properly ad-
justed. When the seed coat is broken, seed-rot fungi have easy access to
the kernel and cause decreased germination. Because of the poor stands
that have been obtained, machine-shelled seed have often been found
unsatisfactory. However, improvement in machines used for shelling, ad-
ditional experience with their operation, and improved seed disinfectants
have resulted in better germination of machine-shelled seed. Relatively
small commercial shellers designed especially for handling seed peanuts

Table 23,—EFFEcT OF TIME OF SHELLING AND SEED TREATMENT ON THE EMERGENCE
oF HAND-SHELLED AND MACHINE-SHELLED RUNNER PEANUTS, MAIN STATION,
AUBURN, 1946

Percentage of emergence of plants from seed

Method of Seed shelled at four different periods prior to planting
shelling treatment

Nine weeks) Six weeks |Three weeks} One day

Percent Percent Percent Percent
Hand........ None 1 80 80, 80
Hand....... .| 2 Percent Ceresan 85 86 82 86
Machine..... None 64 64 51 44
Machine..... 2 Percent Ceresan 80 79 83 80

are now being developed. One such machine kriown as the U. S. D. A.
Peanut Sheller described by Brown and Reed (4) shows much promise
for use by relatively small producers. Using medium-vitality peanuts
shelled on this,machine and treated, Wilson (19) obtained equally good
results from hand- and machine-shelled peanuts. These results are re-
ported in table 23.

Seed Treatment

Seed treatment with proper seed disinfectants has been found to
improve the germination of both hand-shelled and machine-shelled pea-
nuts for seed. Hand-shelled seed and unshelled seed respond less to seed
treatment than do machine-shelled seed. In fact, good stands can often be
obtained from planting the recommended quantities from either hand-
shelled or unshelled seed without treatment. Treating of hand-shelled
seed usually results in 5 to 10 percent increase in emergence. Treatment
of machine-shelled seed, however, often increases the stands by 30 to 50

CULTURAL PRACTICES 191

percent. Wilson (19) of the Alabama Station has tested a number of
seed-treating materials on Spanish and runner peanut seed. He reported
that stands were improved by each of several materials used. However,
some of them gave better results than others. He found that the response
to seed treatment of Spanish and runners was about the same.

Results at the Alabama Station (table 24) show the effect of various
seed disinfectants on emergence of machine-shelled Spanish and runner
peanuts over a period of 5 years. Treatments with 2 percent Ceresan and
DuBay 1452-F (1% ounces of the latter to 100 pounds of seed) were two
of the best. These results are similar to those obtained at the Georgia

Table 24,—-EFFECT OF VARIOUS SEED DISINFECTANTS UPON EMERGENCE OF MACHINE-
SHELLED SPANISH AND RUNNER PEANUTS, Main STATION, AUBURN, ALABAMA

Average number of
Disinfectant Rate of application per | plants from 100 seeds
100 pounds of shelled

seed Spanish Runner

Ounces Percent Percent
NONGs:s sect sits see eee te Ke —_— 48 58
Merc-O-Dust.............--000+- 3 69 67
DOw DO Baw catiiors vata oe bees 3 — 71
Yellow Cuprocide............... 4 65 73
SPerOMl's. esse aelsies neeiee ated ess 4 66 79
A rasan: ese ns cess aaa ne hed Bs 3 71 83
Phy POM sg) creek tiesas Sokaensiance oe ie 2 62 80
Ceresan, 2 percent.............+. 4 78 87
DuBay 1452-F............2.0005 1% 86 85

Coastal Plain Experiment Station (9) where 2 percent Ceresan, Arasan,
Spergon, U. S. R. No. 604 and Dow 9B were found to be of value in the
order named. DuBay 1452-F used at the rate of 3 ounces per 100 pounds
of seed at the Georgia Coastal Plain Station was toxic to the peanut
seed.

The North Carolina Experiment Station (15) obtained quite satis-
factory results from seed treatment of machine-shelled seed. In some
cases the percentage of emergence from treated seed has been more than
twice that of untreated seed. Some results from seed treatment obtained
by the North Carolina Station are reported in table 25. This Station has
also conducted tests with Virginia Bunch and Spanish peanuts, in which
hand-shelled, machine-shelled and unshelled seed of these two varieties
were treated with Arasan. The results of a representative field experi-
ment involving this treatment are given in table 26.

It will be noted that treating machine-shelled peanuts with New

192

THE PEANUT—THE UNPREDICTABLE LEGUME

Table 25.—REsuLTs oF Two SEED TREATMENT TESTS WITH MACHINE-SHELLED
VirciniA BuncH PEANUTS CONDUCTED IN THE FieLp, NortH CAROLINA, 1942

- Emergence from seed receiving different treatments
est®
No New Yellow
treatment | Improved | Spergon Arasan | Cuprocide
Ceresan

Percent Percent Percent Percent Percent
Abvisearnewevegeesars 61.2 80.3 92.2 82.5 60.5
Bice pnatinds ascsina ences 37.8 75.2 63.3 69.7 69.8
Average...........00 49.5 77.7 77.7 76.1 65.2

8 The seed used in tests A and B were from different sources. The seed were composed of large and
medium sizes

Improved Ceresan, Spergon and Arasan increased the emergence in all
cases. However, Yellow Cuprocide was no more effective than no treat-
ment in one test. The Arasan treatment of Virginia Bunch and Spanish
peanuts was effective on both hand-shelled and machine-shelled seed.
However, there was not much increase in the percentage of emergence
from unshelled Spanish variety treated with Arasan.

Results from seed-treatment tests by the Virginia Experiment Sta-
tion during 1939-1945 showed that the stand of peanuts from machine-
Table 26.—RESULTS OF ONE REPRESENTATIVE FIELD EXPERIMENT CONDUCTED TO

DETERMINE EFFECTS OF SEED TREATMENT ON EMERGENCE OF PEANUTS SHELLED
BY DIFFERENT MEtHODs, NORTH CAROLINA, 1942

Emergence from seed receiving different
treatments
Variety
Untreated Treated with
Arasan
Percent Percent
Hand-shelled
Virginia; Bunch: .s0vss sass enw eeaaes cane ee 69.0 76.2
Spanish) .4...00-2.4 nati, seve wes eh brea ayes 68.5 82.6
Machine-shelled
Virginia Bunch................45 Wises cc Nihee 39.1 60.7
OPA MISH sss eau decry soe SE Gee We Se oe Ri ag 57.5 71.7
Unshelled
Virginia Bunch.............. sees eee eee — —
Spanishs.S; bacdtantnd anmet a das egies wits 32.5 39.2

CULTURAL PRACTICES 193

shelled seed can be greatly improved and that the stand from hand-shelled
seed is slightly improved by treating with such disinfectants as Ceresan,
Arasan, Yellow Cuprocide, Dow 9, and U. S. R. 604. On high-vitality
hand-shelled seed, the increase in emergence from treatment is said to
average about 5 percent, whereas on seed of low vitality, the increase is
proportionately larger. Treatment of high-grade machine-shelled seed,
however, increased the stand by 20 to 35 percent. With low-vitality, ma-
chine-shelled seed the increase in some cases amounted to many times
this percentage. High-vitality machine-shelled seed when treated with a
good disinfectant gave about as good a stand as untreated hand-shelled
seed of the same lot. Data from which some of these conclusions were
drawn are given in tables 27 and 28.

Seed may be shelled and treated during the winter months when labor

Table 27.—AVERAGE NUMBER OF PLANTS OBTAINED FROM 100 SEED PLANTED IN
SEED-TREATMENT TEsT, HOLLAND, VIRGINIA, 1943-1944

Average number of plants from 100 seed
Treatment per 100 pounds of seed
Hand-shelled Machine-shelled

seed seed
ATASANY 3 OZis 1.8 cadinlek no hs Aa pa my IS Me Bh 96 91
PA TASAN's 2 OZ 54 tase tip deg iets Yoel Reg eco Beas Oe pete Nara 94 91
Geresan, 4 O706 .#aeeiahsbae ndagean mind andery 95 93
Gerésan; 3! OZic5.6s4c sane iaee veers awe De tO S 95 95
Yellow Cuprocide, 4 oz 94 90
Yellow Cuprocide, 2 oz 93 87
Spergon, 4 OZ. cucae gee sess an ee eee a 95 85
Spergon, 2 02:6. cee ee aees ee ete dere ustee 94 83
Untreated «:.2c:05.25 a ised cane to eee reviews 92 63

Table 28.—AVERAGE NUMBER OF PLANTS OBTAINED FROM 100 SEED PLANTED IN
SEED-TREATMENT TEST, HOLLAND, VIRGINIA, 1945

Average number of plants from 100 seed
Treatment per 100 pounds of seed
Hand-shelled Machine-shelled
seed seed
Wes Re CO4, 22 ie sick pitts aah sues a ete ued Hi tee 91 89
“Ceresan, 40Z.....0.0 00 eee eee e cece eee ene 87 86
Dow 9; 202s we passe qavaeaa dale cee Bae 91 87
Yellow Cuprocide, 4 0Z.......-...000 eee eens 88 87
Arasan, SiOZ 6) id ous oun Pata eA RAR Mee 90 84
Spergon,: 1026.0: ssc0w e's sie ds ae es inne Shae ee ee 86 84.
Fermate; 3 OZsijiie sic cose sie nc kaw aia ou 86 79
Dow 9’ By. 2 O25 4 2 ee ccare gps ah GEE 85 17
Untréated . .. o. cc ceca crores es cs Ge Eee wate 84 67

194 THE PEANUT—THE UNPREDICTABLE LEGUME

is available. In tests conducted at Auburn (19), seed shelled and treated
9 weeks before planting have produced stands as good as those shelled
and treated 1 day before planting. These tests have been in progress for
3 years. In no instance has there been any significant difference in the
stands obtained from seeds shelled on the different dates and treated im-
mediately. The results given in table 23 were obtained in 1946; they are
in agreement with those obtained in earlier years in other tests.

After the seed are shelled and treated, they should be stored in a dry
place. Under such conditions they will keep for several months. Seed
shelled, treated and stored in screened cages at Auburn have germinated
as well 15 months after shelling as they did at the time they were
shelled. Usually, though, it is impractical to carry treated seed over from
one year to another because of web-worms that get into seed.

The method used to apply the disinfectant will depend upon the
volume of seed to be treated. Whatever method is used, it should insure
uniform distribution of the disinfectant over every seed. For best results
each seed should be coated with a film of the chemical dust. Some dis-
infectants will vaporize, and the vapors that enter the sack of seed will
kill the disease-producing organisms on the seed. However, such seed
will become recontaminated as soon as they are placed in the ground,
unless they are covered with a protective coating of the disinfectant.
Thorough coverage is especially important on machine-shelled seed to
prevent entrance of seed-rotting organisms through breaks in the seed
coat.

INOCULATION

Inoculation of peanuts with strains of nitrogen-fixing bacteria has
given varied and inconsistent results. Consequently, many stations do not
recommend use of artificial inoculation. Apparently, many soils carry the
necessary nodule bacteria for this crop. Hence, artificial inoculation
rarely has much effect on yield.

Small increases were obtained by the Alabama Station (1) from the
use of inoculation the first year that peanuts were grown in localities
where the crop was not generally grown. The average results of tests
conducted on Norfolk soil at different locations in 1940 and 1941 are
given in table 29. The data show that the effect of inoculation on Spanish
peanuts was much accentuated by the use of mineral fertilizers applied
in the drill before planting. Also, fertilizers were more effective on this
soil in the presence of inoculation. It was observed that the plants that
grew on the fertilized plots carried substantially more tubercles than the
plants on the unfertilized plots,

CULTURAL PRACTICES 195

Table 29.—INFLUENCE OF INOCULATION AND OF FERTILIZERS ON Hay anv Nut
YIELDS OF SPANISH PEANUTS, MaIN STATION, AUBURN, ALABAMA, 1940-1941

. Yields per acre
Fertilizers per acre® Inoculation
Hay Nuts
Pounds Pounds Pounds
INOIE 5 wire die: 3.5 xn ed aetoende ss - 1,504 1,102
NONnGyievoisccacs pane ote + 1,493 1,117
Superphosphate............. 320
Muriate of potash........... 50 - 1,408 1,097
Superphosphate............. 320
Muriate of potash........... 50 + 1,702 1,281

4 Fertilizers applied in row before planting 70 pounds of shelled nuts per acre.

In other Alabama experiments conducted on the Coosa Valley soils
of the Decatur, Etowah and Fullerton series on the Alexandria Experi-
ment Field, peanuts were planted with and without inocculation in 1941.
The land used had not grown peanuts prior to that year. Both Spanish
and runner were planted on six different areas. The yields of both nuts
and hay of each variety were increased by inoculation to the extent of ap-
proximately 100 pounds per acre. The results of this test are recorded in
table 30.

Most of the chemical treatments used to prevent diseases also kill in--
oculating bacteria, thus rendering artificial inoculation useless. Albrecht
found that Spergon seemed to be an exception to this rule. In tests con-
ducted in 1943 with machine-shelled peanuts, inoculation of Spergon-
treated seed produced approximately 14 percent better stands than un-

Table 30.—AVERAGE YIELDS OF SPANISH AND RUNNER PEANUTS GROWN WITH AND
WITHOUT INOCULATION, ALEXANDRIA EXPERIMENT FIELD, ALABAMA, 1941

Yield per acre
Treatment Spanish Runners
Peanut Hay Peanut Hay
Pounds Pounds Pounds Pounds
Inoculated..............+++- 1,321 1,691 1,508 2,970
Uninoculated............---- 1,208 1,552 1,378 2,870
Increase from inoculation..... 114 139 130 100

196 THE PEANUT—THE UNPREDICTABLE LEGUME

inoculated seed treated with Spergon. The per-acre yields in favor of:
inoculation in the presence of Spergon treatment are:

Spergon-treated, inoculated, 2161 pounds of hay
1303 pounds of nuts
Spergon-treated, uninoculated, 1825 pounds of hay
1170 pounds of nuts
Increase from inoculation, 336 pounds of hay
133 pounds of nuts

CULTIVATION

First cultivation of peanuts consists of running a weeder or rotary
hoe in the same direction as the rows. Successive weedings are made with
the rows or diagonally across the rows and are continued until the plants
are large enough to be broken by such an implement. The practice of
broadcast cultivation is very important in producing peanuts with a
minimum of hoeing. A weeder may be operated following a rain 2 to 3
days before the soil is sufficiently dry to permit plowing. Thus, weeds
may be killed in the seedling stage.

a NOOR PER

ip St,

Figure 2.—Tractor-drawn weeder.

CULTURAL PRACTICES 197

Later cultivation consists of cultivating shallow with sweeps or other
shallow cultivation implements run in the same direction as the rows.
Little or no soil is turned toward the plants except at the first cultivation.
Pegs (pins or young pods) should never be torn loose. The middle should
be kept clean until the vines cover sufficiently to smother weeds.

The principal object in cultivation is to prevent growth of weeds and
grass, which are especially harmful because they reduce yield and greatly
increase labor in harvesting. In fact, very weedy peanuts are nearly im-
possible to harvest. Another object of cultivation is to keep the soil loose
so that the ovary of the seed stem can pierce ne soil readily and thus
allow the nuts to form.

198 THE PEANUT—THE UNPREDICTABLE LEGUME

The practice of covering the young pegs with soil to insure their
pegging down is unnecessary and often is harmful, since it destroys some
of the foliage.

Runner peanuts are usually so cultivated as to leave the land flat.
Spanish or bunch peanuts are cultivated in such a way as to leave the
plants on a bed at the time of laying-by.

Hoeing is necessary in most cases. In favorable years, rapid and
frequent cultivation will destroy all weeds and make hoeing unnecessary.
If peanuts become weedy or grassy, the weeds or grass should be re-
moved immediately. Removal of weeds or grass after the pods begin to
form is difficult and frequently injures the peanuts. The hoeing operation
consists of hoeing the plants when small to remove weeds and grass.
Another hoeing, which consists of “bunching” or removing the bunches
of grass that have been missed during the season, is done at or just before
laying-by. The first hoeing operation is quite expensive, usually because
less than an acre per day can be hoed by one man. The bunching opera-
tion is much less expensive, since one man can cover several acres a day.

Dusting

(Detail of life history and of experiments dealing. with control of insects
and diseases are discussed in later chapters: )

Two major groups of peanut pests are insects and diseases. Two
major insects attacking peanuts are leaf-hoppers and velvet bean cater-
pillars. The two important diseases that attack peanuts are Cercospora
leafspot and Sclerotium, or southern blight.

The use of dusting sulfur, copper sulfur, and combinations of these
with compatible insecticides, such as DDT and Toxaphene, are dis-
cussed in chapters on insect and disease control.

Spray treatments have been used and various spray schedules have
been developed. Use of sprays has been considered impractical for the
following reasons:

(1) More time is required to mix and apply the spray than is required
to dust.

(2) Costs of spray machinery and materials are higher than the
costs of dusters and materials.

(3) There is a greater possibility of burning the foliage by improper
use of spray than by dusting.

(4) Frequently, there is not an adequate supply of water available.

Dusted peanuts are usually dug from 1 to 2 weeks later than undusted

CULTURAL PRACTICES 199

plants. The color of the dusted peanut vines is frequently darker than
the undusted plants. For this reason, it is very important that the time of
digging be determined by examination at maturity of the nuts rather
than appearance of the foliage.

Dusting results in larger yields of peanuts and vines, and in better
quality nuts and hay.

Machinery

Numerous machines are available for dusting. For large-scale opera-
tions, dusting with tractor power take-off equipment is most suitable. In
the case of smaller acreages, mule-drawn dusters of the one-horse type
are preferable. For only a few acres, hand dusting with the small hand-
operated duster is satisfactory. For best results there should be a dis-
tributor (duster nozzle) over each row.

HARVESTING

The peanut plant has a fruiting period covering about 2 months. All
pods do not ripen at the same time. Thus, it is difficult to tell just when
the crop should be dug. If digging is done in time to save the earlier
formed pods, then the later ones will be immature. On the other hand, if
digging is delayed, many of the early-formed pods of Spanish peanuts will
sprout and those of runners and Virginia Bunch are pulled off and left
in the soil. The principal object is to dig the crop at a stage when the
largest number of mature pods can be saved and when the weather is
suitable for curing. If the weather is unsuited for curing, the peanuts
cannot be harvested regardless of the stage of growth. Frequently, insects
destroy the foliage and make digging immediately necessary in order to
save the crop.

The usual method of determining when to dig is to examine the crop
frequently as digging time approaches. At intervals of a few days plants
should be pulled and the stems and pods carefully examined. If many
of the stems, have started to decay, digging should be started at once.
An examination of the pods will show whether or not the pods are ripe.
When a peanut is ripe, the veins of the hulls are prominent and the in-
side of the hull has turned dark. If the inside of the hull is white, the
pod is immature. Another indication of time to dig is that of slight yellow-
ing of the foliage. The leaves become spotted and some of the leaves begin
to drop.

A large amount of labor is required for digging peanuts. Therefore, the
harvest period usually extends from 2 to 3 weeks. This usually means that

200 THE PEANUT—THE UNPREDICTABLE LEGUME

some of the peanuts are dug before the crop is entirely ripe and the last
of the crop is dug after the crop is over-ripe.

Usually it is more difficult to determine when to harvest runner pea-
nuts than is the case with Spanish. The runner peanut may set a crop of
fruit and if conditions become favorable, a new crop of fruit is set on the
ends of the vines. When such a condition occurs, it is necessary to decide
whether to harvest in order to save the first crop of fruit or to delay
harvest and save the second crop. If the second crop appears to be the
larger, it is usually better to delay harvest and save the later crop. The
pods that were formed early will be left in the soil, but these can be
utilized by hogs, and therefore are not lost.

There are many types of
machines used in digging pea-
nuts that work satisfactorily.
None of the machines are ef-
ficient unless the crop is free
of grass and weeds, which.
clog the implements and
make digging difficult. The
most common type of imple-
ment used in digging bunch-
type peanuts is a mold board
plow with a long point at-
tached. This cuts the main
: % root and loosens the soil.
Figure 5.—Turn plow-type peanut digger. For runner peanuts a long

flat bar sharpened and at-
tached to a cultivator is used to run underneath the vines. Peanut-digging
plows with finger like bars that lift the vines from the soil are in use.
Many of the modern diggers are of a 2-row tractor-drawn type.

Another type of digger, somewhat like a potato digger, is coming into
use. This implement lifts and shakes the vines, and leaves them on top
of the ground—all in one operation. A more recent type of digger, when
tractor-drawn, lifts, shakes and puts together two rows at a time, leaving
the vines on top of the ground.

After the peanuts are plowed up, they are allowed usually to wilt for 2
to 8 hours before they are stacked. It is customary to windrow the peanuts
to facilitate stacking either before or after they are wilted. Windrowing .
and shaking may be done by hand, by side delivery rakes, or by special
machinery. In any case the peanuts should be shaken as free of dirt as pos-

CULTURAL PRACTICES 201

two-horse cultivator for plowing up peanuts.

Figure 7.—Tractor with digger blades:

OM Marcas tao He

202 THE PEANUT—THE UNPREDICTABLE LEGUME

3 Secs See
nuts are left to dry.

al
ie}
a
=
oO
00 F
>
eh &
+
oO
re
z.

ndrowing with side-delivery rake pea

ie ee © : :
Figure 9.—Tractor equipped with digger blades and mechanical shaker for handling
two rows at once.

CULTURAL PRACTICES 203

if js Hi
WOES Go Saas

Figure 10.—Shaking and windrowing peanuts by hand.

iy a ot

Courtesy U. S. Department of Agriculture

Figure 11.—Shaking and windrowing peanuts with side-delivery rake after plowing
them up with tractor digger blades.

204 THE PEANUT—THE UNPREDICTABLE LEGUME

sible. The windrows may be combined into one large row for about
every 10 to 14 rows.

Stacking is usually practiced in most of the peanut belt. It is done as
soon as the plants are wilted and before they are dry enough to be brittle.
If left on the ground very long, dew and sunlight tend to discolor the pods,
and the leaves lose the green color and may shatter, which lowers the
hay quality. The vines are stacked around poles, which are firmly placed
in the ground so that the stack will not blow over. The poles are usually
2 to 4 inches in diameter and about 8 feet tall. The poles are placed in the
ground about 18 inches deep. Greater depth makes it difficult to pull up
the poles at picking time. If a shallower depth is used, the poles may blow
over. Two slats, about 3 feet long for runners and about 18 inches long for
Spanish, are nailed at right angles to the poles 14 to 18 inches above the
ground. The slats form two crosspieces on which the first layer of vines is
placed. The crosspieces prevent the vines on the bottom of the stack from
resting on the ground and allow air to circulate, thus facilitating drying.
The center of the stack must be kept open and higher than the edges. The
pods of the bunch type of peanuts are placed toward the center. The
runner types are usually placed on the poles with pitch forks and no at-
tempt is made to place the nuts so that they are not exposed. Twelve to
14 rows of peanuts are placed in the stack row and a sufficient number of
poles are allowed to take care of the stack row. The distance between
stacks will depend on the amount of peanuts on the ground and usually
will vary from 40 to 50 feet. Successive layers of vines are placed on the
stack pole. As the stack nears completion, it is gradually drawn to a point
and a few vines are pressed down over the top to complete the stack. A
little dry grass frequently is placed on top of the stack to help shed water.
In some cases paper or other type of covering is used.

Peanuts are as a rule stacked in the field where the crop is grown,
but sometimes the vines are hauled to a central point where the stacks
are built close together.

The number of poles required per acre is shown in table 31.

The practice of field curing in the windrow is quite common in the
southwestern producing areas. In the Southeastern States it is also some-
times used. In some instances, it is modified by putting the vines in small
cocks. The practice works fairly well if weather conditions are favorable
for curing, but serious damage may occur if there is much rain before the
crop is dry enough to pick. When this system is used, there is always a
discoloration of the pods and the hay is of little value. In the Virginia
and North Carolina area, this system is not used because in those areas

CULTURAL PRACTICES 205

Table 31—NvMBER or STACK PoLEs REQUIRED wiItH Row WIDTHS AND NUMBER
oF Rows PER STACK AS INDICATED; CLACULATED ON Basis OF 40 FEET BETWEEN

POLES
: Number of rows per stack
Row width
7 10 rei 12 14
Poles Poles Poles Poles Poles
per acre per acre per acre per acre per acre
Spanish and Improved White Spanish
24 inches............. _— 54 50 45 39
27 inches............. — 49 45 40 35
30 inches............. — 44 40 36 31
Virginia Bunch Type
33 inches......... seve 57 39 _ = =<
36 inches............. 52 36 _ — _—

there is little demand for peanuts with even slightly damaged kernels.

More recently experiments have been conducted in picking the pea-
nuts green and drying them artificially. Machines for digging and pick-
ing are available. The practice is not yet common and there are not
enough available data to indicate how economical it may be. This method
offers a possibility of reducing the amount of labor involved in harvesting

eames

Figure 12.—Stack pole properly set for stacking runner peanuts.

‘

206 THE PEANUT—THE UNPREDICTABLE LEGUME

¥ a

: Pe pie : t wes 0A. = os 3
Figure 13—Peanut stack about one-third completed. The stack should be firm
throughout with flat top and straight sides until capping is done.

MS cota fos : ae and :
Note heavy capping well above end of stack

Figure 14.—Completed peanut stack.
pole.

CULTURAL PRACTICES 207

peanuts and of standardizing the quality. If it can be done economically
and a satisfactory product produced, it will undoubtedly revolutionize pea-
nut growing.

Picking. Peanuts are curred in a period of 4 to 6 weeks in the stack. In
windrows this period is reduced to about 2 weeks. The peanuts are
properly cured when the stems have become brittle enough to be broken
up and blown out, and when the kernels will split open when rolled be-
tween the fingers. There are two types of peanut pickers: One with a
cylinder similar to a grain thresher and the other a metal mesh with steel

Figure 15.—-Runner peanuts about 3 weeks after stacking. An excellent
stack in foreground. Fair stack at right, and poor stack at left. Note
that bottom of stack has settled away from the capping in the poor
stack. This is the usual result of loose stacking.

teeth that tears the vines to pieces but has no cylinder. With either
type the peanut vine is thoroughly torn apart and the nuts cut from the
stems and vines by a series of revolving saws. The stacks are hauled to
the picker behind a specially rigged cart, on flat-bottom wagons, on a
“dolly” or sled. In case wagons are used, usually one is being loaded with
stacks while another is being unloaded at the picker by feeding the pea-
nuts into the picker. :

In operation of the picker, care must be taken not to feed the machine
so rapidly that the pods are not cleaned properly. If the machine is
operated too fast, many of the nuts are forced out with the hay. The speed
of the fans and the picking machinery must be adjusted carefully so as
to take care of the particular lot of peanuts being picked.

In many cases peanuts are custom picked and there is a tendency to

208 THE PEANUT—THE UNPREDICTABLE LEGUME

rush the job, which results in loss of nuts in the hay and an unnecessary
amount of trash is in the nuts. Only dry pods should be picked. Damp
weather causes difficulty in picking.

After the peanuts are picked, they should be stored thinly or stirred
from time to time until dry. Peanuts should not be stored in bulk until
they are fully dry.

Peanut hay is a valuable by-product of the peanut crop. Its quality
depends on proper harvesting date and method, and also on proper curing
and picking. The hay should be baled immediately after threshing.

Hay left in the field after threshing is exposed to weather and rapidly
deteriorates. Usually hay from vines treated with sulfur to control leaf
spot is higher in quality than that from untreated plants. The amount of
hay varies with the variety and general conditions. Spanish peanuts
usually yield from 1 to 114 tons of hay per ton of nuts, and runner peanuts
1% to 2 tons per ton of nuts.

Many peanuts are grazed by hogs each year in the Southeastern
States. Hogs are used to glean the fields. Frequently peanuts are planted
with alternate rows of corn and peanuts are hogged off after the corn is
harvested. In many instances peanuts are planted solid for hogging. In
most cases the runner-type peanut is used for hogging. The Spanish is
earlier than the runner and is used for early hogging, usually from the
middle of August to the first of October. Runner peanuts remain in good
condition in the ground much longer than Spanish. They are usually
hogged from October through January or February. The yield of pork
per acre varies with the time of harvesting. Early in the season from 2%
to 3 pounds of peanuts are consumed per pound of pork. As the season
advances the pounds of increased growth per pound of peanuts decreases
until in February the figure may become as low as from 5 to 6 pounds of
peanuts per pound of pork.

Hogs should not be turned on the peanuts until the majority of the
nuts are ripe. Hogs do not like immature peanuts and usually will not eat
them. Therefore, if the hogs are turned on when the peanuts are too
green, they root up many of the vines and waste the immature nuts.
Hogs do not like decayed nuts and will not eat them if they can get any-
thing else to eat.

CULTURAL PRACTICES 209

SELECTED REFERENCES
(1) AvBrecnut, H. R.
1944. FACTORS INFLUENCING THE EFFECT OF INOCULATION OF PEANUTS GROWN
ON NEW PEANUT LANDS. Soil Sci. Soc. Proc., Vol. 8.
(2) Batten, E. T.
1943. PEANUT PRODUCTION. Va. Agr. Expt. Sta. Bul. 348.
(3) BeattiE, J. H., Hunn, C. J., MILuer, F. E., Currin, R. E., anD Kyzer, E. D.
1927. EFFECT OF PLANTING DISTANCES AND TIME OF SHELLING SEED ON PEANUT
yieLps, U.S. D. A. Bul. 1478.
(4) Brown, O. A. AND REED, J. F.
1944. Agricultural Engineer. Vol. 25, No. 11.
(5) Funcuess, M. J. AnD TisDALE, H. B.
1924. Ala. Agr. Expt. Sta., Thirty-Fifth Ann. Rep.
(6) Grecory, W. C.
1948. No. Car. Agr. Expt. Sta. PRIVATE COMMUNICATION.
(7) Kitiincer, G. B., Stoxes, W. E., CLark, F., AND WARNER, J. D.
1948. PEANUTS IN FLORIDA. Fla. Agr. Expt. Sta. Bul. 432.
(8) Kine, Gro. H.
1944-45. Silver Anniversary Rept. Ga. C. P. Agr. Expt. Sta.
Qe ==
1945-46. Twenty-Sixth Ann. Rept. Ga. C. P. Agr. Expt. Sta.
(10) McCLetianp, C. K.
1931. THE PEANUT CROP IN ARKANSAS. Ark. Agr. Expt. Sta. Bul. 263.
(11)

1944, PEANUT PRODUCTION EXPERIMENT, 1931-41. Ark. Agr. Expt. Sta. Bul.
448.
(12) McNEss, GeorceE T.
1928. PEANUTS IN TEXAS. Texas Agr. Expt. Sta. Bul. 381.
(13) Mititer, LAwrence I.
1942. PEANUT LEAFSPOT AND LEAFHOPPER CONTROL. Va. Agr. Expt. Sta.
Bul. 338.
(14) ParnwaM, S. A.
‘1942. PEANUT PRODUCTION IN THE COASTAL PLAIN OF GEORGIA. Ga. C. P.
Expt. Sta. Bul. 24.
(15) SHaw, LuTHER.
1943. WHY AND HOW TO TREAT PEANUT SEED. N. C. Agr. Ext. Ser. War
Series Bul. 18.
(16) STANSEL, R. H.
1935. PEANUT-GROWING IN THE GULF COAST PRAIRIE OF TEXAS. Texas Agr.
Expt. Sta. Bul. 503.
(17) SturKIE, D. G.
1934. peanuts. Ala. Agr. Expt. Sta. Leaflet No. 5.
(18) West, H. O.
1942. PEANUT PRODUCTION. Miss. Agr. Expt. Sta. Bul. 366.
(19) Witson, Coyt.
1948, SEED TREATMENT OF PEANUTS, Ala. Agr. Expt. Sta. Leaflet 23. Revised.
(20) Wi1nGaARD, S. A. AND BaTTEn, E. T.
1945, TREAT SEED PEANUTS FOR PROFIT. Va. Agr. Expt. Sta. Bul. 382.

CHAPTER VII

INSECT PESTS

FRANK SELMAN ARANT’

The importance of insect damage to peanuts has not been generally
recognized, even by the peanut industry and agricultural leaders. Text-
books of economic entomology barely mention peanut insects, although
numerous species of pests attack the crop in the field and in storage.
These insects feed on the foliage and underground parts of the growing
plants, suck the juices of pods curing in the field, and infest peanuts and

Figure 1. Velvetbean caterpillar and fall
armyworm ragging the foliage of pea-
nuts. (The larva nearer the fingers in
the picture is the fall armyworm.)

their products in storage and in
transit to markets,

The control of insect pests of
peanuts is a serious problem.
Scores of species attack peanuts
throughout the world, and per-
haps a dozen are of major im-
portance in southeastern United
States. Information on the con-
trol of some of these forms is
sparse and in some instances the
economic status is controversial.
It is the purpose of this chapter
to summarize the available in-
formation on peanut insects and
to point out the need for addi-
tional information. Major em-
phasis is on destructive forms
and species of controversial
status in southeastern United

States.

1¥Frank Selman Arant is head, Department of Zoology-Entomology, Alabama Polytechnic

Institute.

210

INSECT PESTS 211

Velvetbean Caterpillar »

Importance. The velvetbean caterpillar, Anticarsia gemmatilis
(Hbn.), is a serious pest of peanuts in Alabama, Florida and Georgia,
where it appears to be increasing in importance. During the past 10 years
some damage from this insect has occurred locally each year, and severe
outbreaks over the peanut-growing sections of these States were recorded
in 1939, 1944, 1946 and 1948 (65, 52, 6, 7). Prior to this time the insect
had been considered of little or no importance on peanuts, although it
had received some attention on other crops.

A. gemmatilis damage to velvetbeans in Florida in 1903 was described
by Chittenden (28). For several subsequent years, damage from the
insect appears to have been observed primarily on velvetbeans. In 1918,
Watson (149) reported A. gemmatilis attacked peanuts only when the
crop was grown adjacent to velvetbeans, and stated that the adults had
never been known to oviposit on peanuts under natural conditions.
Later Watson (153) reported extensive velvetbean caterpillar damage
to peanuts and soybeans. Additional damage to crops has been listed by
others (46, 73, 65, 50, 122). Purswell (122) concluded that the insect
causes economic damage to peanuts, soybeans, kudzu, alfalfa and velvet-
beans, and also attacks cowpeas, string beans, lima beans, sesbania, black
locust, horse bean and cotton. Severe damage to crops has been reported
from Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina,
South Carolina and Texas.

The velvetbean caterpillar feeds upon the leaves of peanuts. Heavy
infestations cause complete defoliation of the plants, including destruc-
tion of terminal buds. The yield of peanuts is reduced and additional
losses result from the shedding of pods in the soil at harvest (52, 6). The
yield of hay is also reduced.

Reliable data on losses from velvetbean caterpillar are difficult to
obtain. In 1944, the estimated loss in Alabama was placed as high as 10
million dollars, approximately one-third the value of the crop in the State
(122). In 1946, the loss in Georgia was estimated at 4 million dollars,
and the saving resulting from control at nearly 10 million dollars; in Ala-
bama the loss was estimated at 500 thousand dollars and the saving from
control at over 5 million dollars.? The extent of control operations in
Alabama is indicated by the fact that approximately 4 million pounds of
cryolite and 300 thousand pounds of other insecticides were applied in

1946.

2 Estimate compiled by U. S. Bureau of Entomology and Plant Quarantine.

212 THE PEANUT—THE UNPREDICTABLE LEGUME

Description of Stages. Descriptions of the stages and notes on the ap-
pearance of velvetbean caterpillar have been published by several writers.
The descriptions of immature stages given below are by Watson (148) :

Fog

The egg is nearly 2 mm. in diameter and somewhat less in height, and flattened
on its lower surface. It is prominently ribbed and white until about a day before
hatching, when it turns a delicate pink... . The eggs are laid singly, mostly on the
underside of the leaves, although many are found on the upper surfaces and some on
the petioles and stems.

Larva*

First Instar. The newly hatched caterpillar is about 2.5 mm. long and grows
to be from 6 to 7 mm. before molting. The head is light brown in color, rounded,
bilobed; mouth shining; eyes black. The body is of a uniform light green color with-
out any trace of longitudinal stripes. The tubercles are black and conspicuous; setae
also black. The prolegs on abdominal segments 3 and 4 are about equal in size but are
much smaller than those on segments 5 and 6 and are not used for walking. A glance
at the prolegs is the most ready means of distinguishing the first and second instars.
The legs are light brownish yellow.

Second Instar. The markings are now very similar to those of the next instar but
are somewhat less pronounced. The most conspicuous longitudinal mark is the black
border to the lateral line. The papillae are black as in the first instar, but there is
around the base of each a light-colored ring. The first pair of abdominal prolegs, as
in the first instar, is less than a fourth as long as the third, weak, and not used in
walking or clinging ; but the second pair is about half as long as the third. These, too,
are ordinarily not used in walking but occasionally are so used.

Third Instar. Head rather square in outline, strongly bilobed, yellowish; ocelli
black; mouth dark brown. Body cylindrical; all prolegs used for walking, but the
first pair may be somewhat shorter than the others, light yellow; dorsal line pale
white, somewhat broken, margined on each side by a darker border. Subdorsal line
very pale and indistinct, bordered as dorsal line; lateral line indistinct and broken,
narrow, pale white. Substigmatal line wider and continuous but of a paler color than
dorsal and subdorsal. Ventral surface yellowish green. Stigmata brown. Tubercles
black.

Fourth Instar. Dorsal, subdorsal and sub-stigmatal lines more distinct than in
the third instar. All feet used in walking, but the first and to a lesser degree the sec-
ond pair noticeably shorter than the others. Otherwise this instar is very like the
third.

Fifth Instar. Also similar to the third instar, but the longitudinal lines are more
clearly defined. Papillae are now white with brown apexes. In the area between the
dorsal and subdorsal lines there are a few white dots with a brown border. One of
the largest of these is situated near the anterior border and subdorsal line on abdom-
inal segments 1-8. On the metathorax it is double. Stigmatal line is brownish yellow,
broken, widely bordered with white on the ventral margin. In the lighter colored
individuals this line is often a rich yellow bordered by lines of deep pink.

3 Surface attached to the leaf.

4 The description given is of the dark phase. As pointed out by Guyton (65) and others, great

variation in color occurs after the first instar. The vigorous manner in which the larva wiggles
upon being disturbed is an important distinguishing characteristic in the field.

INSECT PESTS 213

Sixth Instar. The stigmatal line is colored like the lighter forms of the fifth
instar, but the pink is usually replaced by brown.

Pupa

Brown in color, smooth and shining. Abdominal segments punctuated with fine
dots which are particularly thick on the anterior half of each segment. Head some-
what pointed. At the end of the abdomen are three pairs of hooked spines, one pair is
much larger than the others. Length 18-20 mm., width 4-6 mm. The pupa is light
green until it is about a day old.

Adult

No entirely adequate description of the adult has been found. A de-
scription based on reports of Chittenden (28), Watson (148), Douglas
(46), and observations of the writer follows:

The moth averages approximately 37 mm. across the outstretched wings from tip
to tip. The body is stout and narrowed at the apex, measuring approximately 12 mm.
from head to tip of abdomen. The color varies from grayish tan to dark reddish
brown. Under a hand lens the wings have a peppered appearance, black specks show-
ing on a lighter surface. A line which may be lighter or darker than the rest of the
wing extends diagonally across the outstretched wings from near the anterior distal
tip of the forewing to the mid-posterior margin of the hind wing. When the wings
are at rest this line may appear as the segment of a circle. The part of the wings
distal to the line is darker than the proximal part. The wings are bordered with a
brown or yellowish line and are heavily fringed with gray or brown. On the under
side of the wings is a row of white dots, consisting of 7 dots on each wing. This color
pattern is less variable than that on the upper surface. In the field, a character of
value in recognition of the moth is its rapid, spasmodic flight. When disturbed it
rises quickly, flies rapidly a short distance, and settles suddenly into the foliage of
the host plant.

Biology. Life-history studies of the velvetbean caterpillar have been
made by numerous authorities (148, 46, 73, 122), but many facts con-
cerning the biology of this species are still unknown. Apparently the in-
‘sect does not overwinter in the United States except in southern Florida.
Watson (148) recorded the presence of adults in southern Florida as early
as May 1 and found the northward flight of the moth reached southern
Georgia and Alabama by September 1. Subsequently, other investigators
have observed the northward migration of moths during the summer
months and it has been assumed that overwintering occurs only in
southern Florida, Cuba and nearby islands. During recent years, the in-
creasing damage and early appearance of the insect in southern Alabama
and Georgia have led to some speculation as to whether the species is be-
coming acclimated to a more northern habitat. Attempts to carry imma-
ture and adult stages overwinter at the Wiregrass Sub-experiment Sta-
tion in southeastern Alabama have been unsuccessful two successive
winters (5). Thus it appears that overwintering does not occur as far north

214 THE PEANUT—THE UNPREDICTABLE LEGUME

as the Wiregrass Station, although larvae have been collected in nearby
Houston County as early as June 21 (6). The northern limit of the
species’ overwintering range is not known.

The moth of the velvetbean caterpillar is active principally at night or
during twilight. Large numbers in flight may be seen along highways by
the light of motor cars. Oviposition also occurs mainly at night or during
dark days. Eggs are deposited singly on the underside of the leaves of
peanuts and other host plants. Some are also placed on the upper surface
and petioles. Rank foliage is preferred for oviposition and there is a tend-
ency to avoid peanut fields where plants are small and foliage sparse,
unless the population of insects is very great.

Development from egg to adult requires approximately 4 to 5 weeks
during late summer and early fall. The time has been reported as ap-
proximately 30 to 43 days on velvetbeans in Florida (148), 30 to 36 days
on soybeans in Louisiana (46) and 32 to 36 days on peanuts in Alabama
(122). The egg hatches in 3 to 5 days and the caterpillar feeds 16 to 26
days. Pupation usually occurs in the soil at a depth of one-eighth inch
to one and one-half inches. Some larvae pupate on the surface of the
ground under litter and occasionally rolled in a leaf, especially on such
plants as soybeans and kudzu. The insect remains in the pupa stage 7 to 15
days during warm weather.

Little is known regarding the biology of the adult of the velvetbean
caterpillar. As mentioned previously, many of the moths fly northward
for many miles and the females then oviposit. The mating habits, pre-
oviposition period, oviposition period, total egg production, and longevity
are unknown. Exact information on the distance traveled by moths in
flight is lacking as is much other pertinent information on the biology of this
pest. It is known, however, that the moth flies much farther north than
the insect can overwinter in any stage. All stages perish during the en-
suing winter.

Several generations of the velvet-bean caterpillar may occur during a
season in Alabama, Georgia, Louisiana and northern Florida. Three dis-
tinct generations were reported in 1929 (46) in Louisiana. Four gen-
erations were reported in Alabama in 1946 from the middle of June to
the first of November (122). Larvae of the second and third generations
cause serious damage to peanuts if the initial infestation occurs early and
conditions are favorable for the multiplication of the insect.

Additional research is needed on the biology of the velvetbean
caterpillar to determine breeding habits, flight, hibernation, host plant
relationships, relation of temperature to development and survival, and

INSECT PESTS 215

factors influencing abundance, such as climatic conditions, diseases, para-
sites and predatcrs.

Control—Natural enemies and climatic conditions are of value in re-
ducing the population of the velvetbean caterpillar but cannot be de-
pended upon for control. Douglas (46) reported seven species of birds, a
predaceous wasp, a hymempterous parasite, and a parasitic fungus at-
tacking the caterpillar. Hinds and Osterberger (73) reported several
parasites and predators, including a Tachinid, Winthemia rufopicta
Bigot, which parasitized as high as 70 percent of the caterpillars. They
also described a parasitic fungus identified (46) as Spicaria prasina
(Maulk.) Saw, considered synonymous with Botrytis rileyi observed by
Watson (148). Apparently the same fungus, described by Purswell
(122), has caused 30 percent fatality to velvetbean caterpillars in fields
near Dothan, Alabama. Insect enemies of the velvetbean caterpillar
include Sphex pictipennis (Walsh), Solenopsis geminata (F.), Calosoma
sayi (Dej.), C. scrutator Fabr., Posidus maculiventris, Proxys punctu-
latus, Stiretrus anchorago (Fab.), Ephialtes aequalis (Prov.), Ophion
bilineatum Say, and Brachymeria ovata (Say). Dry weather also appears
to be detrimental to the multiplication of velvetbean caterpillar.

Insecticidal control of the velvetbean caterpillar on peanuts has been
found profitable. Early control practices consisted of applying arsenicals,
such as Paris Green, lead arsenate, and calcium arsenate, but consider-
able burning of foliage resulted on some crops. Douglas (46) found
sodium fluosilicate is highly effective and safe on soybeans. Ellisor and
Floyd (51) found cryolite to be somewhat less toxic to velvetbean
caterpillar than calcium arsenate and acid lead arsenate, but the degree
of toxicity indicated the possibilities of cryolite as a control for the insect.
Guyton (65) reported the effective use of lead arsenate on peanuts
without injury to foliage. Eddy (48) and Bissell and Alden (16) recom-
mended cryolite on peanuts. English (52) found cryolite and 3 percent
DDT dusts highly effective. Moderate gains in yield of peanuts resulted
from one timely application of these dusts, and where digging was de-
layed 10 days fewer peanuts were lost in the soil on the dusted plots
than on untreated areas. The retention of the pods by the dusted plants at
harvest was especially significant and accounted for most of the benefit
- derived from dusting. Cryolite, DDT, and benzene hexachloride have
been reported as highly effective (6). DDT protected peanuts over the
longest period; protection given by benzene hexachloride was the short-
est. Complete protection from caterpillar damage resulted in gains in
yields of 302 to 573 pounds of dry peanuts per acre on land yielding 946

216 THE PEANUT—THE UNPREDICTABLE LEGUME

pounds without dusting. The peanuts were harvested before much loss
from shedding in the ground had occurred. Loss in the ground was re-
duced by dusting even after the plants were 90 percent defoliated.
Unpublished data (7) indicated effective control of velvetbean caterpillar
with cryolite, 10 percent toxaphene, 2 percent DDT, 1 percent gamma
BHC, 5 percent methoxychlor, 5 percent DDD, and 1 percent parathion
each at the rate of 25 pounds per acre. Five percent chlordane was less
effective.

Cryolite at the rate of 20 pounds per acre is the standard recom-
mendation for control of velvetbean caterpillar on peanuts near harvest.
It is effective and does not injure the foliage. There is no serious residue
problem. DDT is highly effective at rates as low as 0.36 pound technical
material (18 pounds 2 percent dust) per acre (161). It is cheaper and
faster acting than cryolite. Residue studies, however, have shown that
DDT persists on the peanut foliage which is used as hay. The DDT
residue on 13 samples of hay collected in Alabama in 1946 varied from
2 to 31 p.p.m., depending upon the interval between dusting and harvest
and the rainfall during the period (6). All samples of hay containing less
than 7 p.p.m. were from fields on which approximately 6 inches of rain
fell over the 4- to 5-week period between dusting and harvest. In practice,
peanuts are sometimes harvested within 10 days after dusting. When the
DDT-treated hay is fed to livestock, the DDT is stored in the fat and
passed in the milk of the animals. Thus, it is ultimately passed on to
human beings where it is a possible health hazard, especially to young
children consuming large quantities of milk. For these reasons cryolite
is generally recommended in preference to DDT for velvetbean caterpillar
control on peanuts near harvest.

In 1949, Wilson and Arant reported (160) that four applications of
2.5 percent DDT applied during the summer months for leafhopper
control usually control velvetbean caterpillar throughout the season. The
last application made approximately 30 days before harvest does not create
a serious residue problem. Where dusting is necessary within 30 days of
harvest, cryolite or 5 percent methoxychlor is recommended.

Fall Armyworm |

Importance. The fall armyworm, Laphygma frugiperda (A. & S.), is
a periodic pest of peanuts in Alabama, Florida and Georgia. Some
damage occurs each season in these States, and not infrequently the insect
is present in sufficient numbers to cause complete defoliation of peanuts.
Few references to fall armyworm damage to peanuts are found in

INSECT PESTS 217

entomological literature. Hinds and Dew (72) reported peanuts as a food
of this pest, and Robinson (126) reported serious damage in Barbour
County, Alabama. The pest caused severe damage throughout southeast-
ern Alabama and southwestern Georgia in 1948 (6, 7). Control
experiments have shown that fall armyworm may reduce the yield of
cured peanuts as much as 500 pounds per acre (7, 160).

In addition to feeding on peanuts, the fall armyworm attacks
numerous other plants including corn, sorghum, oats and other grasses ;
alfalfa, soybeans, velvetbeans, cowpeas and other legumes, as well as
many other types of plants.

Description of Stages—Detailed descriptions of the life-history stages
were made by Luginbill (93). Briefer descriptions have been made by
H. G. Dyar and published by Chittenden (27). The descriptions given
below of the egg and larva are from Chittenden; those of the pupa and
adult are from Luginbill.

Egg

Eggs [deposited] in a close double layer, one above the other, more or less cov-
ered with fine gray down from the moth; spherical, well-rounded, the base a little
flatter than the apex, uniform; vertical ribs numerous, about 60, small, joined by
distinct crossbars nearly as large as the ribs themselves and forming rectangular or
slightly hexagonal areas; above, the ribs do not diminish till near the vertex, where
they become converted into reticulations, smaller toward the micropyle; color, pearly
pink; diameter, 5 mm.

Larva

First Instar. Head rounded, bilobed, about as high as wide, clypeus triangular,
half as high as the head, without perceptible paraclypeal pieces ; labrum quadrate and
with the mandibles projecting; shining jet black; antennae moderate, pale; setae
short, pointed ; width .25 mm. Cervical shield straight before, rounded behind, jet black,
bearing 4 setae on each side; two more (of which one is scarcely visible) detached
posteriorly, laterally, prespiracular and subventral tubercles single-haired ; anal plate
semicircular, dusky blackish. Body whitish, slightly translucent, tubercles large,
round, black with very distinct, short, black, pointed setae. Arrangement normal, no
subprimaries; on joints 3 and 4, ia and iia small,-ib and iib large, all well separated
and equally spaced; iv and vi single-haired; on the abdomen i, ii, and iii large, equal,
i and ii on joint 12 approximately in a square, iv behind the spiracle and with v as
large as the dorsal ones. Leg shields small, quadrate, black ; ventral tubercles minute,
also black. Feet of joints 7 and 8 slightly smaller than those of joints 9 and 10. After
feeding the larva becomes green from the food.

Second Instar. Head round, slightly bilobed, shining black; width .4 mm. Body
as before, a little thicker, and joints 12 more distinctly enlarged; cervical shield
black; anal plate not cornified, pale like the body, shaded with gray on the sides.
Color whitish, with faint traces of dorsal, subdorsal, lateral, and stigmatal lines.
Tubercles large, black, and distinct as before, the subprimary ones present. Hairs
short, stiff, black. Thoracic feet black, the others pale, with dark shields.

218 THE PEANUT—THE UNPREDICTABLE LEGUME

Third Instar. Head round, shining black, the sides covering the eyes and sutures
of clypeus, pale luteous; width .65 mm. Shields and tubercles shining black, tubercles
large, setae coarse and black. Body greenish gray, dorsal and subdorsal lines whitish,
straight, narrow, and even; ground color darker laterally, ending in a blackish shade
touching tubercle iv, defined on the ventral side. A broad, pale, substigmatal band;
subventer grayish green, shading to the scarcely paler venter. Body uniform, joint
12 very slightly enlarged.

Fourth Instar. Head black, paraclypeal pieces and labrum pale whitish, sides no
longer pale, but filled in with black mottlings; rounded, slightly bilobed, shining ;
width 1.1 mm. Cervical shield black, bisected, not strongly cornified; anal flap dusky ;
tubercles large, black. Body greenish gray, dorsal, subdorsal (at tubercle ii), and
traces of narrow lateral lines pale, as before; substigmatal line broad, white, mottled
with greenish and divided by a central band of this color. Feet dusky; setae distinct,
black, rather long.

Fifth Instar. Head rounded, slightly bilobed ; clypeus large, the paraclypeal pieces
nearly attaining the vertex; mandibles prominent; brown-black, sides mottled with
pale, especially posteriorly, paraclypeal pieces white, as also the verticle suture;
labrum pale, width 1.8 mm. Body cylindrical, normal, joint 12 very slightly enlarged,
feet nearly equal. Above dark brown, a little dotted with pale, venter more greenish,
but also brown mottled. Dorsal line pale, nearly obsolete except on the thorax and
anal plate; subdorsal line distinct, white, straight, a little broken on joints 12 and
13; stigmatal band broad, sharply edged, not inclosing the spiracles, white, nearly
filled in with dark red mottlings. Feet all dusky; cervical shield sooty black, not
strongly cornified, cut by dorsal and subdorsal lines; anal plate dusky, with two
white spots, formed by the broken dorsal line; tubercles distinct, black, with short,
stiff, black setae. ;

Sixth Instar. Head rounded, bilobed, clypeus large, the paraclypeal pieces reach-
ing three-fourths of the distance to the vertex; brown-black, sides posteriorly
mottled with pale, sutures white, all as before; width 3 mm. Body as before, joint
12 very slightly enlarged, feet equal. Blackish brown above, varying in shade, the
lateral space tending to be darker, as also a space each side of the dorsal line;
venter pale greenish, densely mottled. Dorsal line whitish, as broad as the subdorsal
and regular, but much fainter; subdorsal line mottled with pinkish, straight. The
pale mottlings of the body are heavier between tubercles i and ii and across tubercle
iii, suggesting obsolete lines. Slight black streaks bordering the subdorsal line below.
Substigmatal band broad, sharp, the edges a little irregular, white, filled in with pale
red mottlings. Feet all dusky; cervical shield black, very narrowly cut by white
dorsal and subdorsal lines; anal plate dusky, cut by pale dorsal line, with a con-
striction anteriorly. Tubercles cornified, distinct, dark brown, largest on joints 12
and 13; tubercle iv on joint 5 is opposite the upper corner of the spiracle, on joints
6 and 7 below the middle, on 8 at the middle, on 9 above the middle, on 10 at the
upper corner, on 11 low down halfway between the spiracle and tubercle v, and on
joint 12 opposite the lower corner of the spiracle. Setae short, rather stiff, dark.

Pupa

Dark reddish brown, darker on the prothorax, black immediately before emerg-
ence of the adult; labrum separated from the clypeus by distinct suture, quadrate;
fronto-clypeal suture not distinct; libial palpi visible, about one-fourth length of
maxillae; mesothoracic wings reaching to caudal end of fourth abdominal segment;

INSECT PESTS 219

metathoracic wings not visible on the venter, maxillae reaching almost to tip of
wings; prothoracic legs over half as long as maxillae, their femora exposed; meso-
thoracic legs a trifle shorter than maxillae; metathoracic legs showing caudad of
maxillae not projecting from caudal margins of wings; antennae a little shorter than
mesothoracic legs; sculptured eyepiece somewhat broader than the glazed eyepiece;
invaginations of the tentorial arms distinct ; vertex narrow on the meson, broader on
the sides; mesal length of prothorax one-half that of mesothorax; mesal length of
metathorax one-fourth that of mesothorax; cephalic portion of the fifth, sixth, and
seventh abdominal segments and the same portion of the fourth abdominal segment
on the dorsum finely and densely punctured; area around the spiracles slightly
elevated, blackish; caudad of each spiracle is a shallow cavity; spiracles ellipsoidal ;
mesothoracic spiracle extending over half the length between the antenna and the
meson, the area blackish; cremaster consisting of two short, stout, blunt spines;
genital opening of female simple; slitlike, apparently situated on the eighth abdom-
inal segment, the cephalic margins of the ninth and tenth segments curving strongly
forward toward the genital opening in this sex; genital opening of male simple,
slitlike, on the ninth abdominal segment on slight elevation. Length from 14.7 to
17.4 mm. Greatest width 4.5 mm.

Male. Head and thorax ochreous suffused with reddish brown; palpi with black-
ish patch at side of 2nd joint; frons with blackish bar above; vertex of head suf-
fused with fuscous; tegulae with fuscous patches; pectus whitish; fore coxae and
femora suffused with fuscous abdomen ochreous white suffused with reddish brown
leaving slight pale segmental lines, the anal tuft tinged with rufous. Fore wing
ochreous whitish suffused with fuscous and reddish brown, the inner area paler;
subbasal line represented by double oblique dark striae from costa; a black streak
below base of cell curved up to cell at extremity; a minute whitish spot defined by
black on outer side in cell before the antemedial line, which is indistinctly double,
oblique, waved, somewhat bent outwards in submedian fold; claviform represented
by a diffused brownish streak, orbicular whitish defined by black and with pale
brown centre, a whitish bar beyond it and above base of vein 2; reinform with black
and white bar on inner side, its outer edge slightly defined by black and with irregu-
lar white marks at upper extremity; a slight white fork at bases of veins of 4, 3;
an indistinct oblique waved line from lower angle of cell to inner margin; post-
medial line indistinct, double, strongly bent outwards below costa, then minutely
waved, incurved at discal fold and below vein 4, some white points beyond it on
costa; an oblique diffused whitish shade from apex to vein 6, the whitish subterminal
line arising from it, excurved at middle and bent outwards to tornus, some short
black streaks before it in the interspaces at middle; a fine white line before termen
with series of slight black streaks from it to the black terminal striae; cilia brown-
ish with fine white line at base followed by a dark line.5 Hind wing semihyaline
white, the apex suffused with brown; a dark terminal line from apex to vein 2; the
underside with the coastal area slightly irrorated with fuscous, a terminal series of
black striae from apex to vein 2.

Genitalia. Uncus represented by a stout, sickle-shaped hook or spine; gnathos
about as long as the uncus; harpes large and broad, the anal angles not well defined ;
marginal spines prominent; claspers hinged at base composed of stout hooks, one on

5 Var. fulvosa (Male).--Fore wing somewhat more suffused with purplish, the white fascia
from apex indistinct.

220 THE PEANUT—THE UNPREDICTABLE LEGUME

either harpe and attached to it near the anal angle; clavus button-shaped; juxta
composed of a chitinized plate in front.of aedoeagus attached to articulation of harpes
by two stout muscles; ampulla consists of a flap covered with numerous short spines ;
editum is slender, spiny at tip; peniculus oar-shaped ; cornutii composed of 3 groups
of several short spines each.

Female. Much more fuscous brown, the costal area and veins irrorated with grey,
the lines less distinct; the orbicular and reniform with slight whitish annuli, the
former without pale bar beyond it and no white streak at lower angle of cell, the
whitish fascia from apex obsolete.

Biology. Adults of the fall armyworm are active during the night and
in the late afternoon and early morning. The female deposits eggs in
masses on grasses, peanuts or other suitable host plants. The number of
eggs per mass is reported (146) as varying from 9 to 349, with an aver-
age of 143 eggs per mass. One female lays an average of about 1,000 eggs.

The eggs of the fall armyworm hatch in approximately 3 days and the
young larvae feed at first on the surface of the leaves, skeletalizing them.
Later they devour the leaves of the plant. The caterpillars feed both in
the daytime and at night. Occasionally they may be found hiding under
clods at the base of plants, but this habit is not nearly so pronounced as in
cutworms. When food becomes scarce, the caterpillars may migrate in
large numbers seeking additional food plants. Most crops in the path
of the march may be destroyed by this pest. At maturity the caterpillars
enter the soil and pupate.

The life cycle, egg to adult, may be completed in approximately 30
days. The winter may be passed in the adult stage in the southern part of
the insect’s range. Part of the winter may be passed also in the larval
stage (146). Apparently, this species is not able to over-winter success-
fully except in tropical and semi-tropical areas. During the warm months
the adults migrate northward and may cause damage by fall in central
and northern States.

Control. Natural enemies are important in the control of fall army-
worm. Tachinid flies, hymenopterous parasites, and ground beetles are
important enemies of the insect. Vickery (146) lists one species of
Hymenoptera ovipositing in the egg of the fall armyworm and 8 species
in the larvae. Two species of Diptera and one fungus, PBeauveria
globulifera, are also listed as parasites of larvae. The fiery hunter,
Calosoma calidum (F.), and other ground beetles are listed as important
predaceous enemies of fall armyworm (27). The more important
insect enemies are as follows: Chelonus texanus Cresson, Apanteles
marginiventris Cresson, Meteorus laphygmae Viereck, Zele melleus
(Cresson), Sagaritis dubitatus (Cresson), Neopristomerus appalachianus

INSECT PESTS 221

Viereck, Ophionbilineatu3 Say, Euplectrus platyhypenae Howard,
Frontina archippivora Séudder, Archytas piliventris Van der Wulp.
Thirteen species of birds and a large number of insects are listed (93)
as enemies of the fall armyworm.

Insecticides in the form of dusts, sprays and poison baits have been
used in control of fall armyworm on various crops. References to
recommended procedures are too numerous to cite. On peanuts, cryolite
dust containing approximately 90 percent sodium fluoaluminate has been
effective when applied at the rate of 20 pounds per acre. Other materials
which have given effective control in Alabama include DDT, toxaphene
and parathion (6, 7). A 2.5 percent DDT dust is effective against small
larvae but may not kill mature caterpillars. A 5 percent material applied at
the rate of 20 pounds per acre is recommended for full-grown caterpillars.
Ten percent toxaphene applied at the same rate is also recommended.
Two percent parathion is effective but, because of its acute toxicity to
warm-blooded animals, it is not recommended for general use by peanut
farmers.

Where a combination insecticidal-fungicidal dust containing 2.5 per-
cent DDT is applied at intervals during the summer for leafhopper and
leafspot control, fall armyworm is usually controlled satisfactorily on
peanuts (160). If weather conditions and timing of applications are such
that a population of full-grown caterpillars develops, it may be necessary
to apply 5 percent DDT at the rate of 20 to 30 pounds per acre in order
to effect control. Ten percent toxaphene and cryolite appear to be slightly
more effective against the mature larvae than DDT at concentrations
of 5 percent and less. DDT and toxaphene are not recommended on
peanut hay within 4 weeks of harvest.

Corn Earworm /

Importance. The corn earworm, Heliothis armigera (Hbn.), attacks
growing peanuts and frequently causes light to moderate damage. Oc-
casionally, severe outbreaks of the insect occur. The writer has observed
rather severe damage in 1946 and 1949 over widespread areas in south-
eastern Alabama. The caterpillars feed on the foliage of peanuts, ragging
the plants and in some instances defoliating them. This insect not in-
frequently occurs in mixed populations with velvetbean caterpillar and
fall armyworm. Heavy losses in yield from defoliation or from severe
ragging of leaves may occur. Although corn earworm may be considered
one of the major pests of peanuts during certain seasons in Alabama,
Florida and Georgia, entomological literature contains almost no references

222 THE PEANUT—THE UNPREDICTABLE LEGUME

to earworm infestations in peanuts. Merkl (100) lists peanuts as one of
the principal crops in Alabama being damaged by this insect but based his
conclusion on unpublished records of the Alabama Agricultural Experi-
ment Station. So far as the writer is aware, serious damage has not
been reported in the Virginia-Carolina area.

Description of Stages. The various stages of the corn earworm have
been described by several investigators. Descriptions given below are
taken from the sources indicated.

The egg has been described by Phillips and Barber (113), Quaintance

and Brues (124), and others. The description of Quaintance and Brues,
follows:

Egg
Width, 0.48 mm.; height, 0.50 mm. Shining, waxy white, faintly tinged with
yellowish. The form is almost dome-shaped, except that it is slightly narrower at

the extreme bottom and widest about the basal third. Base flat and apex obtusely
rounded.

The larval and pupal descriptions of Ditman and Cory (45) follow:

Larva

First Instar. Length (soon after hatching), 1.5 mm. Head and thoracic legs, shiny
black. Body newly hatched larva very pale and rather transparent; after some feed-
ing, opaque and creamy yellow. There is a very slight tendency to darker and lighter
longitudinal stripes, at least in larvae nearly ready to molt the first time. Setae of
body of rather medium length, black; on head, some are black and others of a lighter
color. Cervical shield and minute setigeral warts dull brownish black; also the
prolegs externally, and the anal plate. Around each setigeral wart is a poorly de-
fined circular space of whitish beyond which the generally yellow color of the body
appears. The characteristic minute dermal spinules of the older larva are scattered
and very indistinct in this instar.

Second Instar. Length, 3.4 mm. Appearance much the same as in first instar.
Differs in that the setigeral warts are much broader and show up clearly to the
naked eye. The dermal spinulation is more pronounced and general. The longitudinal
stripes are but little more evident, if any, than in the previous stage. In the first
two or three instars the larvae have a semi-looping gait as do the younger larvae of
some of the cutworms.

Third Instar. Length, 7.0 mm. Head, olive brown with darker brown mottlings,
especially on each side near vertex; bears a few fine setae. Cervical shield black or
slightly brownish, with two short white lateral stripes. Body entirely covered with
minute blackish spinules, appearing like a “sand-paper” surface as compared with the
skin of most of the related caterpillars. Four narrow white dorsal stripes and a broad
white band laterally, alternated’ with olive brown. Setigeral warts prominent, shiny
black, and obtusely cone shaped rather than nearly flat as in previous instars. Setae
moderately long and shiny black. Dorsal abdominal warts are larger, especially on
first and second segments. Thoracic legs black; prolegs black on their sides both
experiorly and on the mesal surface. Crochets black.

INSECT PESTS 223

Fourth Instar. Length, 11.4 mm. Appearance much as in third instar. Differs in
the fact that some of the dorsal stripes laterally now appear broken into short, ir-
regularly disposed lengths interrupted by dark ground color. There is a broader
lateral white band in or near which the spiracles lie.

Fifth Instar. Length, 17.9 mm. In general, this stage marks the change to greater
contrasts in the markings and to more brilliant colors. The appearance of red hues,
as on the ventral surface and in the paler portions of the body markings, is now
quite general. Head, orange brown with fine pale setae. Cervical shield and setigeral
warts as before, but the latter bearing pale setae. The shield may lose its dark color
in many specimens, however. All legs pale; claws of thoracic legs and crochets of
prolegs are brownish. Two continuous mid-dorsal white lines now enclose a darker
area appearing as a blackish band, in the middle of which lies a third white line.
Dorsum laterally to white spiracular band transversed by short white lines on a red
and gray ground which becomes darker near the lower edges and tends to concentrate
in segmental dark patches in some specimens.

Sixth Instar. Length, 24.8 mm. Appearance much as in the fifth instar, but in
general more brightly colored and showing more pronounced individual variation in
the nature of the markings. Cervical shield not so dark, and less distinct from the
surroundings in many cases, although in some types of larvae it is very distinct.

Pupa '

The pupa, just after it is rid of the larval skin, is very soft and delicate and
almost larviform. It is pale green on the head.and thorax; the wings are transparent
with the venation showing as whitish lines; the abdomen is whitish and opaque, with
shades of rosy pink dorsally, and orange-colored spiracles. A large transverse rosy
spiracle anteriorly bordered with white lies on each side of the prothorax; a trans-
verse median rosy spot between the eye; and four black dots on each eye.

In a half hour after the molt, the pupa has begun to contract and press its ap-
pendages into-the places habitually taken by them and the pupa. The colors are
hidden by the darkening and hardening of the chitinous coat of the pupa. This change
to the natural shiny brown of the pupa takes place rather slowly over a period of
a day or more. The first portions of the body to darken are the head and dorsal
regions of the thorax and abdomen.

Measurements of twenty-two pupae showed that there is comparatively little
variation in size in this stage. The length was found to average 19.1 mm., ranging
from 17.6 mm. to 20.6 mm. The breadth of the pupa at the widest point across the
back or dorsum is a little greater than the greatest depth from the dorsal to the
ventral surface. The average measurement in the first cases was 5.5 mm., while the
average depth was 5.4 mm.

The original description of the adult (53) was translated by Ditman
and Cory (45) as follows:

Adult

A bombyx, with wings deflexed and yellowish ; with a middle spot‘and posterior
obsolete streak rather obscure. Habitat, islands of Sotith America. Collector, Father
Smith. Of medium size. The antenna simple. The body yellowish with a more obscure
middle spot. Posteriorly with an obsolete streak which is spotted with very small

224 THE PEANUT—THE UNPREDICTABLE LEGUME

punctures. Hind margins brownish. Hindwings yellowish, with posterior margin
fuscous.

Biology. Studies on biology of the corn earworm have been made by
numerous workers (81, 112, 13, 45). The insect over-winters in the pupal
stage which may be found 2 to 6 inches below the surface of the soil. The
adult emerges in the spring or early summer, and the females soon
begin depositing eggs. Eggs are laid singly on the leaves and terminal
buds of many plants. When corn in the silking stage is present the eggs
are deposited on the silks. One female may lay as many as 3,000 eggs.
On peanuts, the caterpillars feed. on the leaves, causing ragging of the
foliage, or even complete defoliation of the plants. When the larva is ma-
ture it pupates in the soil. Time required for complete development, egg to
adult, is approximately 30 days under favorable conditions.

In addition to feeding on peanuts, this insect is a major pest of several
other crops including sweet corn, field corn, cotton, tomatoes, tobacco,
soybeans and other plants. It is commonly called corn earworm, tomato
fruitworm, or bollworm, depending upon the crop it infests.

The moths are most active at dusk or during warm, cloudy days. They
are strong flyers and may migrate for considerable distances before de-
positing eggs. There appears to be a tendency for the migration to be
northward.

Control. The literature available on control of corn earworm is too
extensive to review in this paper. Winburn and Painter (162) reported
46 hymenopterous and 22 dipterous insects that aid in natural control. An
enormous amount of research has been conducted on the chemical and
cultural control of Heliothis armigera on corn, cotton, tomatoes and
several other crops. However, very little information is available on con-
trol of this insect on peanuts. Experiments conducted at the Wiregrass
Substation of the Alabama Agricultural Experiment Station have shown
that the insect may be successfully controlled on peanuts with cryolite,
DDT or toxaphene (5, 7, 8). The insect is most readily controlled when
the larvae are small. Full-grown caterpillars are somewhat resistant to
most insecticides. Cryolite should be used undiluted at the rate of at least
20 pounds per acre for control of earworms on peanuts. Two and one-
half percent DDT dust at the same rate is effective against small larvae. It
is not highly effective against mature forms. Where a population of fully
grown caterpillars develops before control measures are applied, a dust
containing at least 5 percent DDT is required for satisfactory results. Ten
percent toxaphene is highly effective against small larvae and moderately
so against mature forms.

INSECT PESTS 225

The recommended practice for control of corn earworm in the Ala-
bama-Florida-Georgia area is applications of 2.5 percent DDT at 7- to
10-day intervals in a regular dusting program for control of insects and
diseases (160). Where infestations of last-instar larvae are found 5 per-
cent DDT, 10 percent toxaphene, or cryolite should be used. Infestations
which occur within 4 weeks of harvest should be controlled with cryolite
if the vines are to be used for hay.

Potato Leafhopper

Importance. The potato leafhopper, Empoasca fabae (Harr.) may
attack peanuts wherever they are grown commercially in the United
States. The related species Empoasca facialis Jac. is reported on peanuts
in South Africa (107) ; E. solana DeLong occurs on peanuts in Hawaii
(76) and E. flavescens (F.) on peanuts in Dutch East Indies (89)..

In addition to injuring peanuts, E. fabae attacks a wide variety of
plants including potato, bean, clover, alfalfa, soybean, eggplant, rhubarb,
cotton, dahlia, apple and many other plants. Several common names
have been used for this insect, each referring to a host plant. It might be

pper damage to peanut leaflets. (Upper leaflet normal; two lower
leaflets damaged.) ;

Figure 2. Leafhop

226 THE PEANUT—THE UNPREDICTABLE LEGUME

called peanut leafhopper, but ‘the official common name is potato leaf-
hopper, a name suggested by Ball (12) to indicate potato as a preferred
host.

Both adults and nymphs of the insect feed upon peanuts by sucking
juices principally from the lower epidermis and veins of the leaves. Some
damage may result also from the deposition of eggs. As a result of leaf-
hopper damage to peanuts, the tips of the leaflets turn yellow and as the
damage becomes more acute the yellowing progresses toward the base
of the leaflets and some of the tips may appear burned. Damage is more
severe during dry weather. A field of infested peanuts may have a yellow-
ish appearance rather than characteristic green. Batten and Poos (14)
reported a dwarfing as well as yellowing of foliage in severe infestations
in Virginia. Metcalf (102) reported a disease called “pouts’’ resulting in
peanuts from the mass effect of toxins injected by E. fabae; the leaflets
turned dark at the tips, and the whole leaf sometimes blackened and
died. Apparently, this condition was severe “hopperburn” ; it should not
be confused with a dwarfed condition, also sometimes called “pouts,” re-
sulting from thrips damage.

There is considerable evidence that leafhoppers reduce the yield of
peanuts (117, 14, 104, 7). In some instances, however, there has been
no clear differentiation between the effect of damage from leafhopper
and Cercosporo leafspot. There is need for more exact information on
losses caused by potato leafhopper to Spanish, runner and jumbo types of
peanuts. The losses should be measured in terms of yield of peanuts and
yield and quality of hay.

Description of Stages. The potato leafhopper was originally described
by Harris in 1841 (66) as Tettigonia fabae and the Genus Empoasca was
established by Walsh in 1864. Subsequently, numerous descriptions have
been published under several synonymous names. The descriptions of im-
mature stages given below are from Ackerman and Isely (1) ; that of the
adult is from DeLong (42):

Egg

Egg elongate, subcylindrical, very delicate, slightly curved from end to end, some-
what rounded at both ends, but more so at the anterior end. When first deposited it
is rather transparent, but in a few days it changes to a pale yellow while a small
white cap forms at the anterior end through which the red eyes of the immature
nymph are perceptible. Average length 0.82 mm., width 0.25 mm.

Nymph >
First instar. Pale white, changing to a light yellowish green after feeding. Eyes

dull red. Small pale spines on the dorsal side of the head, thorax, and abdomen; the
latter with four spines to each segment arranged in two longitudinal rows along

INSECT PESTS 227

each side, one spine situated dorso-laterally, the other ventrolaterally. Posterior
margin of metathorax blunt. First two segments of antennae pale, the remainder
dusky. Average length 1 mm.

Second instar. General color light yellowish green. Eyes losing some of their
red color. Posterior border of metathorax sharp in outline. First two segments of
antennae light yellow, remainder dusky. Average length 1.30 mm.

Third instar. General color pale yellowish green. Eyes almost pearl white. Body
more robust than in first two stages. Wing pads appearing as lateral buds extend-
ing to the hind margin of the first abdominal segment. Spines darker and more
prominent. Average length 1.85 mm.

Fourth instar. Head and thorax yellowish green; abdomen yellow. Eyes pearl
white. Wing pads extending to hind margin of second abdominal segment. Spines
prominent. Average length 2.1 mm.

Fifth instar. Head and thorax pale green; abdomen yellow. Wing pads extending
to, or nearly to, the hind margin of the fourth abdominal segment. First two antennal
segments green, remainder dusky. Body broader than in previous instar. Average
length 2.6 mm.

Adult

Pale green, usually with a row of white spots on anterior margin of pronotum.
Length 3.5 mm.

Vertex bluntly angled, a little longer on middle than next to eye and about one-
third wider between eyes than length at middle.

Color. Yellowish to pale green, markings variable; vertex frequently with
pale or dark-green spots; pronotum usually with a row of six or more pale spots
along anterior margin, sometimes missing or indistinct; elytra greenish subhyaline.

Female genitalia. Last ventral segment moderately produced and roundedly
truncated.

Male genitalia. Valve produced and rounded or bluntly angled; plates triangularly
tapered to pointed apices, which are frequently upturned; lateral processes of the
pygofers rounded on inner margins and broadened on apical half, then concavely
rounded to narrow attenuated tips, which are slightly curved inward; spines of
tenth segment broad, with tips narrowed and directed downward. This combination
of characters will distinguish Empoasca fabae from closely related species.

Biology. Many studies have been made on the biology of potato leaf-
hopper on potatoes, beans and other crops, but none has been made on
peanuts except in the form of general observations. Beyer (15) reported
the results of life-history studies of the insect on beans in Florida and
Poos (114) reported similar studies on cowpeas in Virginia. There like-
wise are rather comprehensive reports from other sections on the biology
of the insect (54, 1, 41).

The potato leafhopper apparently over-winters only in the Gulf-Coast
States where some breeding may occur throughout most of the winter. As
the weather becomes warm in the early summer it spreads northward and
causes damage to a variety of crops during the summer and fall. Cold
weather presumably destroys all stages of the insect except in its south-

228 THE PEANUT—THE UNPREDICTABLE LEGUME

ern range, where the winter may be passed on any green host plant such
as alfalfa, clovers, castor beans and other plants. Beyer (15) found it
throughout the winter on castor beans. It is possible that hibernation may
occur, either in the egg or adult stage, in part of the insect’s range, but
all evidence on hibernation is negative.

The time required for development from egg to adult is 18 to 24 days
during warm weather (42, 14). As the weather becomes cool, this period
may increase to 60 days. Approximately 5 to 10 days are required for
incubation of eggs and 8 to 15 for nymphal development. Females mate
and begin ovipositing in 3 to 5 days in the veins and petioles of the leaves.
Approximately 60 eggs per female are deposited over a period of 30
days during warm weather. A maximum oviposition of 131 fertile eggs
has been reported in Florida (15).

The average longevity of the female is approximately 35 days, al-
though a maximum of 123 days has been reported in Virginia (114).
Longevity of males is somewhat shorter. Six generations per year have
been reported in Virginia and Florida.

Additional research is needed on potato leafhopper to determine its
development on peanuts, overwintering habits, and the relation of de-
velopment on various wild and cultivated host plants to damage in
peanuts. ‘

Control. Natural enemies are apparently of relatively minor value in
suppressing the population of potato leafhopper. Heavy rainfall reduces
infestation in peanuts. A parasitic fungus, Entomophthora sphaerosperma
Fresenius, causes a disease which is of considerable importance. The
disease has been reported from Florida (15), Arkansas (1), Iowa (54),
and other localities. Eighty percent of the insects may be diseased, and as
high as 37 percent of those affected may perish. Chrysopid and coccinellid
larvae are important insect predators of the potato leafhopper, Chrysopa
plorebunda Fitch and Hippodamia 13-punctata being species commonly
observed. The predaceous bug, Triphleps insidiosus Say is also a natural
enemy as are certain spiders, ants and birds. Insect parasites in potato
leafhopper appear to be rare, although Anagrus armatus Ashm. is re-
ported common in Iowa.

Numerous studies have been made on insecticidal control of potato
leafhopper on potatoes, beans and other crops. Some studies have been
made also on peanuts. Poos and Batten (117) found that 4:4:50 Bor-
deaux mixture applied to peanuts in Virginia increased the yield 21 per-
cent. In 1938 these investigators reported more extensive experiments
with sulfur and copper dusts and sprays which resulted in very substantial

INSECT PESTS 229

increases in yield. Miller (104) reported similar results. In none of these
reports was there a clear differentiation between increases from leafhopper
and disease control, although leafspot is given as a factor. The same
authority (106) has reported the potato leafhopper as the most injurious
insect of peanuts in Virginia, and stated that sulfur applied for leaf-spot
control repelled and controlled leafhopper, even on undusted areas in
small-plot experiments. Poos (116) found that 2 percent DDT reduced
the infestation of the insect on peanuts and Poos, Grayson, and Batten
(120) reported some increase in yield of peanuts and hay from control
of leafhopper, but none of the differences was significant. Non-significant
increases were also recorded (5) in yield of sound, shelled peanuts in
Alabama in 1947 from the use of DDT sprays and dusts on runners. In
1948b, however, the dusting of Spanish peanuts 4 times for leafhopper
control in Alabama resulted in decreased infestation and in average gains
in yield as follows: 2 percent DDT, 302 pounds dry peanuts per acre
gain; 2 percent DDT in 90-10 sulfur-copper, 468 pounds per acre; 20
percent toxaphene, 470 pounds (7). Two percent gamma BHC and 5
percent chlordane were less effective. Four applications of dust to runner
peanuts for leafspot and leafhopper control resulted in average gains in
yield as follows: Sulfur-copper, 90-10, 264 pounds of dry peanuts per
acre; 2 percent DD¥, 339 pounds per acre; sulfur-copper plus 2 percent
DDT, 444 pounds. Where 10 dustings were made with DDT throughout
the season, no significant gains were recorded. In a non-replicated, pre-
liminary test, 9 dustings with 20 percent toxaphene for thrips and leaf-
hopper control resulted in excellent control of both insects and a 67 per-
cent increase in yield over the check.

Thus it appears that control of potato leafhopper on peanuts is profit-
able. It also appears feasible to control leafspot and leafhopper in one
operation with a combination insecticide-fungicide. Little is known, how-
ever, regarding the relative value of controlling the insect on Spanish,
runner and Jumbo peanuts. Little is known regarding the value of con-
trol on different soils, although observations indicate that damage is more
severe on poor than on more fertile soils; presumably more profits might
be derived from control on the less fertile soils.

A combination insecticidal-fungicidal dust has been recommended
(160) for control of leafhopper and leafspot in one operation. The dust
mixture recommended contains 2.5 percent DDT, 3.4 percent copper, and
at least 65 percent sulfur. Four to 5 applications of the dust are applied
at approximately 10-day intervals. The last dusting should be 4 weeks
before harvest, if the peanut vines are to be used as hay. The DDT-sulfur-

230 THE PEANUT—THE UNPREDICTABLE LEGUME

copper dust is recommended for peanuts in the Alabama-Florida-Georgia
area.

A dust containing 1 percent DDT and 90 percent sulfur has been
recommended (119) for dusting peanuts in the Virginia-Carolina area.
Three applications are recommended at 3-week intervals, beginning July
10 to 15.

Tobacco Thrips v

Importance. Thrips damage to young peanuts is widespread over most
of the peanut-producing areas. The tobacco thrips, Frankliniella fusca
(Hinds), is the principal species involved, although the flower thrips,
F. tritici (Fitch), also infests peanuts, living mainly in the flowers (120).
Heliothrips indicus occurs on peanuts in Sudan (32). Taeniothrips dis-
talis Ky. and T. longistylus Ky. are reported damaging peanuts in India
(125).

Apparently, the first thrips injury to peanuts in the United States
was observed by Watson (149) when he collected F. fusca from this crop.
In 1922 he reported widespread damage in Florida during the spring of
1919. Since that time the insect has been observed throughout most of the
peanut-growing section of the country. In addition to peanuts, F. fusca

di ’ : te fe

Figure 3. Leaflets of peanuts showing typical thrips damage.

INSECT PESTS 231

attack tobacco, cotton, beans, peas, Irish potato, oats, cocklebur, dew-
berry, evening primrose, crab grass, tomato, vetch and many other plants
(77, 49).

Thrips attack peanut plants *most severely while they are small. The
upper surface of the developing leaflets are rasped by the insects and as
the leaflets unfold they have a scarred and even deformed appearance.
Farmers often refer to damaged peanuts as “‘possum-eared,” a term quite
suggestive of the appearance of the leaflets. The plants fail to grow prop-
erly. Where infestations are severe, stunting occurs and the damaged
peanuts recover slowly and perhaps incompletely. Thrips damage usually
disappears or becomes less acute, concurrently with increased rate of
growth of the plants, the more rapid growth probably resulting from
the nitrogen fixation and favorable climatic conditions.

Thrips injury has been referred to as “pouts.” The peanuts, in farmer
language, were said to pout until blooming time when growth became
more rapid (115). Another condition caused by potato leafhopper has
also been called “pouts.” It is apparent that the term “pouts” is not
specific, and should not be used to designate thrips injury (133).

It has been assumed by many that peanuts grow out of the stunted
condition resulting from thrips infestation and little permanent harm re-
sults. Recent studies discount this view. As a result of experiments at
Beltsville, Maryland, it was concluded (116) that thrips reduced the yield
of peanuts as much as 37 percent. Substantial increases in yields were
reported, in some instances, from control of thrips in Maryland and
Virginia (120). The author (7) found that control of thrips on runner
peanuts resulted in the setting of fruit earlier than on undusted plants,
although most of the early crop was lost in the ground at harvest. It ap-
pears that permanent damage may result from thrips infestation resulting
in decreased yield of peanuts.

The degree of damage doubtless varies with the type of peanuts, fer-
tility of the soil, and weather conditions as well as with the insect infesta-
tion. Apparently, damage is more severe and recovery slower on poor
than on fertile soils. Additional research is needed to clarify these points.

Description of stages. Two forms of F. fusca adults occur (49), one
with shorter wings than the other. The relative length of wings varies also
with the distention of the abdomen at the time of measuring. It is not
clear from the literature whether the original description of the insect
(69) was of the short- or long-winged type. In 1905, however, the insect
was described (70) under the name Euthrips nicotiannae from long-
winged females, These descriptions are given below ;

232 THE PEANUT—THE UNPREDICTABLE LEGUME

Egg

The eggs are deposited in the tissues of the stem and leaves.

Larva, first stage

Length about 0.23 mm.; width of mesothorax 0.11 mm. General shape fusiform.
Color of posterior part of thorax and entire abdomen pale yellow; elsewhere pearly
white. Head quadrate; eyes reddish. Antennae 0.15 mm. in length; distinctly four-
segmented; basal segment cylindrical, short; second ovate, slightly shorter than
the third; third slightly conical, the apex joining the second; fourth fusiform,
widest near the basal fourth, about equal in length to the other three. The fourth seg-
ment is distinctly annulated, the second and third indistinctly so; setae are present
on all segments, most numerous on the fourth. Legs translucent white, stout. Abdo-
men tapering posteriorly; with ten segments, the first eight nearly equal in length,
the ninth twice and tenth three times the length of the preceding. Each abdominal
segment with longitudinal rows of setae, the ninth with two and tenth with four
spines that are four times the length of the setae.

Larva, second stage

Length from 0.6 to 1.17 mm.; width of mesothorax from 0.14 to 0.2 mm.; shape
same as in first stage. Color of thorax and abdomen yellowish, with exception of the
last abdominal segment. Head quadrate; antennae with four segments, the fourth
being more distinctly annulated than in the first stage. Abdomen with the setae in-
creasing in length posteriorly; ninth and tenth segments about equal in length,
each less than twice the length of the others.

The young nymph or prepupa

Length, 0.52 to 0.62 mm.; width of mesothorax, 0.10 to 0.12 mm. Antennae
translucent, extending forward, much shortened and composed of five segments,
first two cylindrical and very short, third and fourth globose, fifth tapering to the
apex. The last segment of the abdomen is set with four spines by use of which the
young nymph seems to protect itself, when approached by another the abdomen
being turned upon it. The wing sheaths are very noticeably separated, the upper one
extending to the middle of the second segment, the lower one to the middle of the
third segment. The legs are translucent white, stout.

The full-grown nymph or pupa

Length, 0.68 to 1.22 mm.; width of mesothorax, 0.15 to 0.20 mm. Shape similar
to the adult. Color yellowish; head, antennae, wing pads, legs, and caudal segments
of the abdomen varying to pearly white. Antennae extending to the middle of the
prothorax. Three yellowish ocelli between the eyes, the latter dark red. Wing pads
so closely applied as to appear single, extending to the middle of the fifth abdominal
segment; length from head to tip of wing pads 0.39 mm. The abdomen is noticeably
contracted longitudinally; greatest width, 0.24 mm.; longest setae, 0.078 mm.

Adult

Average length, 1.05 mm. (0.95 to 1.13 mm.) ; averagé breadth at middle of
abdomen, 0.27 mm. (0.225 to 0.285 mm.). General color of head and thorax light
brown or tawny yellowish-brown; abdomen dark brown.

Head about one and one-half times as wide as long, frequently slightly retracted
under anterior margin of prothorax ; occiput transversely wrinkled, posterior margin
strongly thickened and darker in color; anterior margin slightly bisinuate, cheeks

INSECT PESTS 233

approximately straight and parallel. Eyes dark red in color, not protruding, occupy-
ing together fully one-half the width of the front of the head and being one half as
long as the head; margins around eyes pale yellow in color; surface of eyes finely
faceted and slightly pilose; three ocelli present, well separated, posterior ones con-
tiguous with yellow borders to eyes, pale yellow in color and margined inwardly
with pale-orange crescents; one moderately stout dark spine in front of each
posterior ocellus; postocular spines weak and inconspicuous. Mouth cone reaching
nearly to posterior edge of the prosternum, tapering abruptly; maxillary palpi
slender, three-segmented. Antennae inserted slightly below front margin, approxi-
mate at base, about two and one-half times as long as the head and approximately
equal to breadth of mesothorax.

Segment 1 is rounded, three-fourths as long as broad; 2 is broad as/1; following
segments about three-fourths as thick; segments 3 to 6 are constricted at bases, be-
coming more stout successively. Color of segments 1 and 2 uniform light brown; 3
to 5 pale yellow at bases, shading to brown at outer ends, each succeeding segment
from 3 to 6 becoming darker in color; 6 to 8 are dark brown. Spines upon segments
2 to 5 are of medium size, but not very conspicuous. Color of head varying from
gray-brown to yellow-brown.

Prothorax about five-ninths as long as broad and slightly longer than the head;
sides rounded, slightly wider at hind than at fore angles; one stout spine at each
anterior, and two stouter spines of equal size at each posterior angle; anterior
marginal pair of spines about one-half as long as those at front angles; usual row
of five spines on each side of hind margin, of which number 4 is equal in strength
to those on the front margin. Mesothorax nearly one and one-third times as wide as
the prothorax, broadest posteriorly, sides curving outward; mesonotum without
conspicuous spines, posterior margin forming an obtuse angle in middle. Metathorax
slightly narrower than mesothorax, sides nearly parallel, broader than prothorax
at posterior edge; metanotum bears two pairs of spines at front edge, the inner
pair as strong as those at front angles of prothorax. Wings present (probably
reduced at some season of year), average length about 0.68 mm., not reaching to the
tip of the abdomen, breadth equal to about one-thirteenth of their length; fore
wing has two longitudinal veins, each bearing stout spines set at regular intervals;
fore wings shaded ash gray, hind wings gray only along basal three-fourths of
midvein; spines on wing veins dark brown and conspicuous; costa bears 19 to 24
spines; fore vein, 13 to 18; hind vein, 10 to 12; scale, 5; interior of scale, 1; fringe of
hairs on costa of fore wing quite heavy, in length exceeding the breadth of the
wing. Legs of medium length, lighter than body in color, pale yellow, shaded more
or less with brown on upper side of middle of femora and tibiae; a pair of stout
brown spines at inside of tip of each tibia, small brown spines scattered along femora
and tibiae; spines standing in two rows on inner side of hind tibiae are weak and
only about four in each row.

Abdomen nearly cylindrical to eighth segment, then tapering abruptly to an
acute tip; color uniformly dark brown; a still darker-colored narrow chitinous
thickening extends across dorsal side of segments 2 to 8 near anterior edge. Three
or four quite stout and rather conspicuous dark-brown spines stand at each side of
dorsal plates on 2 to 8; six rather prominent spines stand in a row on posterior
edge of ventral plates 2 to 7; terminal spines stout and prominent; tenth segment
split open along dorsal median line.

234 THE PEANUT—THE UNPREDICTABLE LEGUME

Biology. Development of the tobacco thrips is gradual, but approaches
a complete change (55). Eggs deposited in tissues of the foliage hatch in
about 7 days in South Carolina (156). The immature form passes
through two larval stages, during which feeding occurs, the two stages
requiring 5 to 6 days. According to Hooker (77), the mature larva
“crawls to some obscure nook,” becomes inactive and pupates.® This stage
is quiescent and does not feed. At the end of 3 to 4 days the adult emerges
and shortly begins feeding. The time for development from egg to adult is
approximately 16 days, the period being shorter in warm weather and
longer when the temperatures are relatively low.

Breeding of the tobacco thrips is continuous throughout the warmer
months. Five overlapping generations have been reported (49) in South
Carolina from April 10 to October 18. The female lives for an average of
approximately 30 days and deposits 50 to 60 eggs (156). Nonfertile eggs
produce males and fertile eggs apparently produce only females (135, 49,
157). Males live for a shorter period than females and are usually less
numerous in the field.

The tobacco thrips presumably hibernate under grass or in other
protected places. It is possible that intermittent breeding takes place on
wild and cultivated host plants during the warmer periods of the winter
in the southern range of the insect, but specific evidence on this point is
lacking. So far as is known, only the adult females over-winter (49).

Volunteer peanuts are a factor in breeding destructive population of
thrips in Alabama, Florida and Georgia. Many peanuts lost at harvest
remain in the ground over winter and germinate the following spring.
Usually these volunteer plants emerge a few weeks earlier than the regu-
lar crop. The thrips multiply on the volunteers and then migrate to the
younger plants, where peanuts follow peanuts in rotation. Doubtless other
early host plants are also of importance in this respect.

Much additional information is needed on the biology of the tobacco
thrips with emphasis on overwintering habits, succession of host plants
in relation to injury to peanuts, and development of the insect on peanuts.

Control. Heavy rainfall is one of the most effective natural controls
of tobacco thrips. This fact was noted as early as 1907 (77). Predaceous
insects are also of value in reducing the population. A true bug,
Triphleps" insidiosus Say, was reported as feeding upon F. fusca (77 ).
The ladybird, Hippodamia convergens Guerin, and a lacewing, Chrysops

®The closely related species F. tritici usually pupates in the ground (157). It is possible
pangeon of F. fusca may occur in the soil as well as on the host plant.
7 Orius.

INSECT PESTS 235

sp. have been reported as predators of F. tritici (157) and these forms
probably prey on F. fusca also.

Chemical control of tobacco thrips is feasible. The first treatments
consisted of nicotine-soap sprays (77, 49) and rotenone (86). Following
the use of tartar emetic (108) against onion thrips, Thrips tabaci Lind.,
the material was used on peanuts and other plants in the greenhouse with-
out injury to the crops (3). Tartar emetic sprays were used on peanuts in
the field, but the applications were too late for successful control (115).
Poos (116) reported successful control with DDT in the form of 2 per-
cent dust, 0.66 percent sprays, and 10 percent aerosols and with tartar
emetic sprays. Satisfactory control of tobacco thrips on peanuts with
significant increase in yield from the use of DDT and BHC dust and
sprays has been reported (120). The most effective treatment consisted of
three applications of an emulsion containing 4 percent DDT applied by
atomizing at the rate of 10 gallons per acre. The author (5) found 3 per-
cent DDT dust more effective than 20 percent Sabadilla, 1 percent
rotenone, or 1 percent nicotine. A spray containing 1.5 percent water-
dispersable DDT was much more effective against the thrips than 3 per-
cent dust. In 1948, he reported 2 percent Gamma BHC and 20 percent
toxaphene applied as dusts at the rate of 20 pounds per acre gave much
better control than 2 percent DDT dust.

Data on gains in yield of peanuts resulting from control of tobacco
thrips are somewhat contradictory. One study (120) reported increases
as high as 36 percent in the weight of green pods in some experiments
and no increases in others. A second study (7) reported an increase in
the weight of peanut pods set early on DDT and BHC plots but, as men-
tioned previously, most of the early crop was lost in the ground at harvest.
In a nonreplicated preliminary test 20 percent toxaphene dust applied for
thrips and leafhopper control resulted in 810 pounds dry peanuts® per
acre more than was harvested from undusted peanuts. It appears that
gains in yield from control depend upon the severity of the thrips infesta-
tion, the efficiency of the control, the type of peanut concerned, fertility of
the soil, weather conditions, and other factors. Additional research is
needed on these points.

W hite-Fringed Beetle

Importance. The white-fringed beetle, Pantomorus leucoloma (Boh.)®
is potentially the worst pest of peanuts in southeastern United States,

8 Seven percent moisture content. : :
® Also Lagen as Graphognathus leucoloma fecundus (Buch.); other forms including Pantomorus

(Graphognathus) peregrinus Buch., G. leucoloma striatus (Buch.), G. leucoloma dubius (Buch.)
are also of economic importance,

236 THE PEANUT—THE UNPREDICTABLE LEGUME

although at present its limited distribution prevents widespread losses to
the crop. This pest’s first appearance in the United States was in 1936
when it was found causing damage to cotton and peanuts in northern
Florida (154, 155). Shortly thereafter it was discovered in southern
Alabama. In spite of rigid quarantines and intensive control work which
has restricted the dispersal of the pest, it is established?° in 115 counties
in seven Southern States. The infested area in some counties is very
small. The distribution of the white-fringed beetle, by States and counties,
is given by G. G. Rohwer of the U. S. Bureau of Entomology and Plant
Quarantine as follows:

AvLaBAMA: Baldwin, Chilton, Coffee, Conecuh, Covington, Crenshaw, Dallas,
Escambia, Geneva, Jefferson, Lowndes, Mobile, Monroe, Montgomery, Wilcox.

Fiorina: Escambia, Holmes, Oklaloosa, Santa Rosa, Walton.

GeorciA: Baldwin, Ben Hill, Bibb, Bleckley, Bulloch, Burke, Candler, Clarke, Clay-
ton, Clay, Cobb, Coffee, Coweta, Crawford, Crisp, DeKalb, Dodge, Dooly,
Emanuel, Evans, Fulton, Habersham, Harris, Houston, Irwin, Jasper, Jefferson,
Johnson, Laurens, Macon, Monroe, Montgomery, Muscogee, Newton, Peach,
Putnam, Richmond, Screven, Spalding, Sumter, Talbot, Tattnall, Taylor, Telfair,
Toombs, Treutlen, Troup, Turner, Twiggs, Washington, Wheeler, Wilcox,
Wilkinson.

Louistana: Iberia, Jefferson, Orleans, Plaquemines, St. Bernard, St. Tammany,
Tangipahoa.

Mississippi: Attala, Covington, Forrest, Grenada, Hancock, Harrison, Hinds,
Jackson, Jefferson Davis, Jones, Lamar, Montgomery, Pearl River, Perry, Pike,
Rankin, Simpson, Stone.

Nort Carotina: Anson, Bladen, Brunswick, Cumberland, Craven, Duplin, Jones,
Lenoir, New Hanover, Onslow, Pender, Robeson, Sampson, Wayne, Union.

Sout Caroiina: Richland, Fairfield.

The white-fringed beetle is native to Argentina, Chile and Uruguay
in South America. It has been introduced into the United States and also
into Australia (9, 147).

Larvae of the white-fringed beetle feed upon underground parts of
peanuts and damage the stand and yield. Adults feed upon the foliage.
Uncontrolled, heavy infestation may cause a complete loss of the peanut
crop. One report (170) showed an average of 283 larvae per square yard
in peanut fields and upon emergence as high as 44 adults on one plant.
In addition to peanuts, the insect feeds upon several hundred other species
of plants,1! including cotton, velvetbean, soybean, lespedeza, lima bean,
okra, sweet potato, cowpea, chufa, corn, tomato, clovers, many orna-
mentals, and numerous other cultivated and wild plants.

Description of stages. The adult white-fringed beetle was originally

10 1948.
11 Two hundred thirty-four specimens in one locality in Alabama (147).

INSECT PESTS 237

described in 1840 by Boheman as Naupactus leucoloma. In 1939,
Buchanan (20) placed the insect in the genus Pantomorus and described
it from specimens collected at Florala, Alabama. Very brief descriptions
of the egg and larva have been made by several investigators.

Egg

The egg is approximately 0.9 mm. long and 0.8 mm. wide, and is oval in shape.
The color when freshly deposited is milky white; the color changes to dull light
yellow after 4 or 5 days.

The eggs are deposited in masses, ranging in number from a few to as high
as 60 or more, but the usual number is from 15 to 25. The individual eggs and
masses are covered with a gelatinous substance which makes them adhere to one
another and to objects or the soil—Young ef al. (170).

Detailed technical descriptions of the larva are not available to the
writer. A very brief description by Young ef al. (170) follows:

Larva

The full-grown larva averages approximately one-half inch in length. The body
is yellowish white, fleshy, more or less curved, legless, and sparsely covered with
hair. It consists of 12 much-folded segments, which are interrupted by two sub-
lateral longitudinal grooves running the length of the body. The dorsal portions of
the segments are bulging; the ventral portions are flat. On the sides, above the
longitudinal separating grooves, small spiracles are present on all segments except
the second, third, and twelfth (last).

Anderson (2) has published a key with drawings for separating
Naupactus (Pantomorus) leucoloma from related species. This key is
reproduced below:

1. With a group of several spinules dorsally on stipes at proximal end of the
longitudinal row of strong setae of maxillary mala 2
Without spinules at proximal end of the longitudinal row of strong setae of
maxillary mala Pantomorus godmani (Cr.)

2. Eusternum of mesothorax with minute spinules!? between and behind the two
sternal setae. Scutellar setae I, II, and IV on the first four abdominal seg-
ments slender and awl-shaped (— subulate)............. Artipus texanus Pierce
Eusternum of mesothorax without minute spinules.12 Scutellar setae I,
II, and IV on the first four abdominal segments stout and spindle-
shaped (= fusiform) H 3

3. Margin of posterior third of head capsule broadly arched. Paired epipharyngeal
sclerome distinctly U-shaped, basal part with distinct anterior margin which
forms a clear-cut angle with exterior margin of inner arm, and with inner
arm about twice as long as antero-posterior extent of base .. Naupactus, n. sp.
Margin of posterior third of head capsule ogival. Paired epipharyngeal
sclerome not distinctly U-shaped, basal part with obliterated anterior margin,
exterior margin of inner arm roundly ‘connected with interior margin of

12 The presence or absence of these spinules can be ascertained readily on specimens treated
with caustic potash and on uncleared specimens when properly lighted, by studying them with a
magnification of about 75 diameters. i

238 THE PEANUT—THE UNPREDICTABLE LEGUME

outer arm, and with inner arm not longer than antero-posterior extent of
base Naupactus leucoloma Boh.

Adult

Buchanan’s 1939 description of the adult follows:

Length, 8-12 mm. Brownish gray to gray, apical declivity of elytron usually
paler than disk, the latter sometimes indistinctly variegated with gray and pale
brown. Scales moderately dense, setae long and conspicuous, elytral scales in general
broader than those on head and pronotum; elytral setae of unequal lengths, the
longer ones fine, often somewhat kinky apically in dried specimens and two or
three times as long as the shorter ones, the latter brown to whitish; elytral puncture
rows, at low magnifications, appearing as narrow, dark lines.

Vestiture on head and rostrum brownish in general, white above and below eye
and on side of rostrum below scrobe, the scales on subapical area and on mandible
very small, often somewhat coppery or greenish, the setae on front inclined, those
above eye and on rostrum above suberect; nasal plate with its posterior margin
elevated; median groove much widened anteriorly, the widest portion sometimes
about one-fourth width of dorsum of rostrum; scape reaching hind margin of eye,
funicular segment 2 considerably longer than 1, often nearly twice as long, longer
than 3 and 4 together; eye distinctly elliptical. Prothorax wider than long (about
7 to 5), sides broadly and subevenly rounded; pronotum with broader white and
narrower brownish scales, the white ones forming a narrow, median line toward
apex and base (rarely complete), a curved, often indistinct, stripe beginning oppo-
site elytral interval 3, and a lateral stripe which is often incomplete anteriorly, the
disk sometimes with small, vague, scattered, whitish spots; pronotal setae curved,
inclined on disk, more nearly erect laterally; pronotum (with scales removed)
irregularly punctate and feebly rugo-granulate, median groove feeble or obsolescent.
Elytral intervals faintly convex, each with about 3 or 4 confused rows of setae, the
longer ones more abundant on apical declivity, the length of each longer seta equal
to or greater than the width of the interval ; white stripe covering interval 7 through-
out, about apical two-fifths of interval 6, and basal half or more of interval 8, the
stripe bordered mesad (on striae 5 and 6) by a broken, usually indistinct dark line,
and bordered laterad (on stria 8) by a narrow, blackish line. Body beneath scaly and
setose, the setae longer and more nearly erect medially, the abdominal scales pro-
gressively finer from base to apex, abdominal vestiture sparser medially; metaster-
num a little longer than in peregrinus. Legs with abundant, mostly setalike, prostrate
and suberect vestiture ; fore tibia with short, well separated denticulations; posterior
face of hind tibia with a usually distinct ridge from base to about middle.

Biology. Only one generation of the white-fringed beetle occurs an-
nually. The eggs are deposited on the surface of the ground, usually on
or next to debris (sometimes in the soil) during the summer and fall. All
adults are females and each beetle deposits an average of slightly less than
800 eggs. The eggs develop parthenogenetically, hatching in about 2
weeks during warm weather. The larvae pass the winter in the soil and
cause damage to crops, principally the following spring and summer.
It is at this time the stand of peanuts may be seriously damaged. Adults

INSECT PESTS 239

emerge from May until November (169), the peak of emergence coming
in July. Rainfall stimulates emergence. The beetles feed a few days and
gradually disperse over the nearby areas. Since the elytra are fused to-
gether and the insect cannot fly, dispersal is by crawling and the distance
traveled is less than 1 mile. Eggs are deposited and the adults die 2 or 3
months after emergence. Apparently few beetles over-winter in southern
Alabama (169, 170) but adults have been found throughout the winter in
the vicinity of New Orleans, Louisiana (91).

Control. Natural enemies are apparently of minor importance in con-
trol of white-fringed beetles. Strong (141) reported that no natural en-
emies of P. leucoloma had been found in studies through 1938-39. Glaser
et al. (61) reported a nematode, Neoaplectana glaseri Steiner, parasitizing
P. leucoloma and related insects. Swain (142) reported N. glazeri attack-
ing P. peregrinus and P. leucoloma; also N. chresima Steiner in P. pere-
grinus. Later he reported (143) Diplogaster sp. capable of parasitizing
white-fringed beetles, but of minor importance.

Much of the first control work on white-fringed beetle was in the
nature of locating infestations, confining the insect in local areas, sup-
pressing and, if possible, eradicating it. Federal and State quarantines
have been in force and clean-up campaigns have been conducted. Research
stations have been established at Florala, Alabama; Gulfport, Missis-
sippi; New Orleans, Louisiana; Fort Valley, Georgia; and other local-
ities, by the U.S. Bureau of Entomology and Plant Quarantine in co-
operation with State agencies.

Much progress has been made in the control of this insect on peanuts
and other crops in recent years. Calcium arsenate and cryolite dusts,
clean cultivations, herbicides for the destruction of wild host plants, and
the use of soil fumigants such as methyl bromide and carbon disulfide
were among the first control recommendations (111). More recently
DDT has shown great promise. DDT has been reported (166) to be 69
to 74 times as effective as cryolite. As little as 0.125 pound of DDT per
100 gallons of spray gave a higher kill on peanut foliage than 12.5 pounds
of cryolite (165). In experiments at Florala, Alabama, (167, 168) 5
pounds technical DDT per acre, in the form of a dust or dissolved in
zylol and mixed with the upper 3 inches of soil, gave complete mortality
of newly hatched larvae. Smaller dosages gave complete mortality of
summer-hatched larvae, but not of those hatched in late fall. When mixed
with the soil at the rate of 10 pounds per acre and above, DDT gave
complete mortality of newly hatched larvae the year following application,
ie., the second year. In the presence of white-fringed beetle larvae, pea-

240 THE PEANUT—THE UNPREDICTABLE LEGUME

nut plants on soil treated with DDT at rates of 25, 50 and 100 pounds
per acre, yielded 48 percent more peanuts than those on untreated soil.
Thus it appears that control of white-fringed beetle on peanuts by treat-
ment of the soil with DDT is feasible. Dusting the foliage of peanuts to
kill the adults is also feasible but, where soil treatments are employed,
may not be necessary. Incidental control may be had by dusting for con-
trol of potato leafhopper.

Information available on the control of white-fringed beetle has been
summarized (68). DDT is the most effective insecticidal treatment
known for control of the pest. It may be applied to the soil for control of
larvae or to the foliage of plants for control of adults. Ten pounds of
technical DDT per acre has remained effective in the soil during a 5-year
period, and the tests are still in progress to determine the length of
effectiveness. ;

The insecticide may be applied as dusts or sprays. For spraying, 50°

percent wettable powder in concentrations of 2.5 to 5 percent has been
most effective.

In treatment of foliage to kill adults of the white-fringed beetle, DDT
should be applied at the rate of 14 to 1 pound of technical per acre at
2- to 3-week intervals during the season of beetle emergence. The insec-
ticide may be applied in the form of dusts or sprays. Sprays are usually
prepared from wettable powder or emulsifiable concentrates.

Since the major part of the research on white-fringed beetle is being
conducted by the U. S. Bureau of Entomology and Plant Quarantine, this
agency should be consulted for latest recommendations on control.

Only limited information is available on the effect of rotation and
other cropping practices on control of the white-fringed beetle. Additional
research is needed on these points. Additional information is also needed
on the long-time effect of soil treatments with DDT on productivity, soil
organisms, fish and wildlife, and water supplies.

Soil Insects

Several species of soil insects attack peanuts and cause an undeter-
mined amount of damage. In addition to the white-fringed beetle, which is
discussed in another section, damage to underground parts is caused by
several species, including southern corn rootworm, larvae of the banded
cucumber beetle, two species of wireworms, white grubs, and the lesser
cornstalk borer.

One of the first references of damage to peanuts by soil insects was
made by Fink (56), who found southern corn rootworm, Diabrotica du-

INSECT PESTS 241

odecimpunctata (I), attacking young peanut pods in Virginia; the nuts
within the pods were devoured. Following this report, peanut damage
from this insect received little attention until recent years. An average of
12 to 28.1 percent of the pods was reported as injured during 1945 and
1946 in a study made in Virginia (64). D. duodecimpunctata and larvae
of the related species, D. balteata Lec., were found attacking peanut pods
in Alabama (5). Because of the difficulty of distinguishing between the two
closely related species of larvae, no attempt was made to determine rela-
tive abundance. However, the large number of recently transformed D.
balteata adults found in pupal cells in the soil around the peanuts indi-
cated this species was the predominant one. In 1947 Arant (5) observed
as high as 35 percent of the pods injured in some fields, but in this in-
stance a wireworm, Heteroderes sp. appeared to be doing much of the
damage. Other soil pests appear to be of less importance.

Figure 4. Peanut pods damaged by soil insects (wireworms and Diabrotica larvae.)

242 THE PEANUT—THE UNPREDICTABLE LEGUME

Southern Corn Rootworm. This insect is the larva of a 12-spotted
leafbeetle, Diabrotica duodecimpunctata (F), commonly called the
spotted cucumber beetle. The life history and habits of the insect are well
known (144, 82, 4, 137). Both adults and larvae are polyphagic in their
feeding habits, several hundred species of plants serving as hosts. The
foliage of cucurbits and many of the legumes are among the preferred foods
of adults. Eggs are deposited in the soil and the larvae develop upon un-
derground parts of many plants including young corn and the pods of
peanuts. The time for development from egg to adult is 30 to 40 days dur-
ing warm weather. Adults over-winter only in the Southern States. Dur-
ing the summer months, many adults migrate northward and cause dam-
age to cucurbits and other crops.

The extent of the damage caused by this species to peanuts has not
been clearly evaluated. Apparently the insect is more ‘destructive in Vir-
ginia than in Alabama.

Banded Cucumber Beetle. The banded cucumber beetle, D. balteata
Lec. is a pest of beans, vetches, cucurbits, alfalfa, tomatoes and many
other vegetables, fruits and ornamental plants. It is restricted to warm
climates, occurring in the U. S. in the Gulf Coast States and California.
It is distributed in Alabama from the central part of the State south-
ward (127). The insect is found in the northern extremities of its range
only in late summer and fall.

The banded cucumber beetle has been known in Mexico for many
years. In 1905 it was found in Texas (29) and in 1922 in Alabama (127).
Little is known regarding the habits of the larva. It will feed on under-
ground parts of peanuts, corn, string beans, and doubtless many other
plants. Using corn as food for the larvae Robinson (128) found that
‘ approximately 30 days were required for development from egg to adult
during warm weather. The number of generations, seasonal abundance,
overwintering habits, and food preferences of larvae and adults in the
peanut-growing areas are largely unknown. There is a need for ad-
ditional research on this insect and an evaluation of its damage to peanuts.

Wireworms. Wireworms of the genus Heteroderes!® were found by
the writer damaging peanut pods in Alabama in 1947. Larvae of the
genus Cebrial® were also collected from peanuts.

The wireworm, Heteroderes laurentii Guer., is widely distributed in
the Southeastern States and causes economic damage to a variety of
crops, including corn, snapbeans, potatoes, lespedeza and sweet potatoes
(31). So far as the writer is aware, there is no record of damage from
Cebria sp. in Alabama or adjoining States.

13 Identification by Dr. W. H. Anderson, U. S. Bureau of Entomology and Plant Quarantine.

INSECT PESTS 243

Although definite proof is lacking, it is probable that H. laurentii
is the species which attacks peanuts. Unlike some wireworms, this
species completes its development within one year. It prefers cultivated
lands to sod areas. This and other species of the genus Heteroderes are
limited to tropical and subtropical areas (87).

The major facts regarding wireworm damage to peanuts are yet to
be determined.

White Grubs. The larvae of Strigoderma arboricola (F.), have been
reported doing serious damage to peanuts in Virginia (105). The grubs
attacked. the peanut pods and often devoured the nuts. Soil fungi
(Rhizoctonia) apparently invaded the pods through abrasions in the shell
and caused rotting of the peanuts. The damage was more severe on soils
fairly high in organic matter. The grubs caused 85 percent loss in some
fields.

The adult of these grubs is a beetle (Rutelid) 10 to 12 mm. long. The
head, thorax and scutellum are blackish green in color and the elytra are
dull brownish yellow (18). The beetles feed on the flowers of wild and
cultivated roses and on blackberry blossoms and fruits. On collecting
adults from many other plants, Grayson (63) concluded that neither
the larva nor the adult was host specific for peanuts, and that grub dam-
age to peanuts in Virginia was of a minor nature during 1944 and 1945.

Lesser Cornstalk Borer. The lesser cornstalk borer, Elasmopalpus
lignosellus (Zell.), is widely distributed over southern United States,
Mexico and South America. The larva is slender and greenish.in color
with indistinct transverse bands of a lighter color on the anterior margin
of each segment ; it is usually a little less than one inch long when mature.
The adult is a yellowish brown to blackish-colored moth with a wing
expanse slightly less than one inch.

The larva feeds on corn, beans, cowpeas, sugar cane, peanuts,
sorghum and many other crops. Damage is caused by the insect tunnelling
in the stem of the host plant. When not feeding, the larva usually rests in
a tube-shaped web near the surface of the soil. Crops on thin sandy soils
are injured most seriously. Four generations a year have been reported
in South Carolina and Mississippi, each requiring 4 to 5 weeks (94, 95).

There is a strong belief in southern Alabama that the lesser cornstalk
borer is a serious pest of peanuts. Presumably the pest bores in the
stems, killing branches or entire plants. During two seasons, the writer
has not been able to find any serious damage to peanuts which could be
definitely attributed to lesser cornstalk borer. It is well known, however,
that the population of this species reaches destructive levels only at inter-

4
244 THE PEANUT—THE UNPREDICTABLE LEGUME

vals over a period of years (95). It is possible that serious destruction
does occur during some seasons.

Other Soil Insects. Several insects not previously discussed are re-
corded in the literature as attacking the pods and underground parts of
peanuts. These records include the following: Japanese beetle, Popillia
japonica Newn., attacking peanuts in Japan (159) and a potential pest in
the United States; termites in many parts of the world; a mealybug,
Pseudococcus sp. on peanut roots causing severe damage in Puerto Rico
(138) ; mealybug, P. solani Ckll., occurring on peanut roots but causing
little damage in Florida (23) ; pineapple mealybug, P. brevipes (CkIl.) on
peanut pods in Tanganyika (67) ; citrus mealybug, P. citri (Risso), and
also Phenacoccus hirsutus Green on roots of peanuts in Egypt (78) ;
larvae of the yam beetle, Heteroligus claudius Klug., killing as high as 70
percent of seedling peanuts in the Province of Nigeria (88) ; two ants,
Solenopsis fugax Latr. and Tetramorium coespitum L., a mole cricket,
Gryllotalpa gryllotalpa L., and three species of beetle larvae, Pentodon
idiota Hbst., Agriotes gurgistanus Fald., and Podonta daghestanica Reitt
in North Caucasus (132) ; the mole crickets, Scapteriscus acletus R. & H.
and S. vicinus Scudd., on peanuts in southeastern United States (163) ;
two ants, Eciton caeca Latr. and Ectatomma ruidum Roger, in Central
America (21) ; the earwig, Euborellia stali Dohrn, causing as high as 20
percent damage to peanut pods in southern India (25) ; several species
in Senegal including termites, Termes natalensis Hav. and T. bellicosus
Semath which gnaw pods, and Odontotermes vulgaris Hav. which attacks
the nuts themselves; white grubs, Schizoncha africana Cast., Anomala
plebeja Ol., Adoretus umbrosus F., and Podalgus (Crator) cuniculus at-
tacking underground parts; the beetle, Scydmaenus chevalieri boring
into pods and the ants, Monomorium bicolor Em. and Dorylus fulvus
Westu. eating seeds of perforated pods (131).

Control. Few studies have been made on control of insects attacking
underground parts of peanuts. Soil treatment with DDT and benzene
hexachloride has been found to reduce southern corn rootworm injury
to corn (60). Results of control experiments on southern corn rootworm
on peanuts in Virginia (64) showed that DDT applied to the soil at the
rate of 50 pounds of technical material per acre resulted in a reduction of
61 to 68 percent in the number of pods injured; yield records were not
taken. The writer (5) found that soil treatment with DDT, BHC, chlor-
dane and toxaphene reduced the injury to pods by soil insects on repli-
cated plots in Alabama. In 1949, he found that dusting with toxaphene
or DDT reduced damage from Diabrotica larvae (8). Effective control

INSECT PESTS 245

is reported by Fronk and Dobbins (59) from soil applications of 1 to 1%
pounds gamma benzene hexachloride, 5 pounds parathion, 40 pounds
toxaphene, or 67 pounds DDT. Additional research is needed on soil
insects, their economic status, and control.

Insects Attacking Peanuts and Peanut Products in Storage

A host of insects attack peanuts and peanut products in storage, some
times causing severe damage. Some damage may occur in storage on
farms, but the major losses are to buyers, processors, wholesalers, and re-
tailers of peanuts and products derived from them. Insect infestations are
much heavier in peanuts after they are shelled (121, 17). Salted peanuts,
peanut meal, peanut butter, candies and other confections are readily in-
fested by insects and the peanut trade must continuously combat these
pests.

Many of the forms infesting grain, milled products, dried fruits and
other foods also attack peanuts. The exact number of species infesting
peanuts is not known, but over 50 species infest grain and grain products
(11). Among the more important stored-products pests attacking peanuts
are Indian meal moth, almond moth, saw-toothed grain beetle, flour
beetles, cadelle, dermestids and others.

So far as the writer is aware, no adequate estimates are available
on annual insect damage to peanuts and their products in storage. A 3-
million-dollar loss in the United States was estimated in 1911 (121). In
1943 the Food and Drug Administration (58) reported that, of the
7 million pounds of imported nuts?* examined in 1943, over 5 million
pounds were denied entry because they were wormy or damaged. The
major reason for the high percentage of rejections was insect infestation
in large shipments of peanuts from Africa.

Different species of insects infesting stored peanuts and peanut prod-
ucts vary greatly in actual damage caused. However, heavy insect infesta-
tions render the products unfit for the edible trade regardless of the
extent of destruction wrought.

Indian Meal Moth. The Indian meal moth, Plodia interpunctella
(Hbn.) is a handsome moth with a wing expanse of nearly 34 inch (11).
The fore wings are reddish brown with a coppery luster on the apical two-
thirds; the proximal third is whitish gray; the hind wings are dusky
gray. The larva is a dirty-white caterpillar often with a pinkish or green-
ish tint ; when full-grown, it is about % inch long. According to Popenoe
(121) this is the most important insect pest of stored peanuts in the

14 Several kinds, including peanuts.

246 THE PEANUT—THE UNPREDICTABLE LEGUME

United States. It also causes damage to peanuts in many other parts of
the world (131, 103, 140, 109, 96, 22). Larvae of the Indian meal moth
feed upon shelled peanuts and spin silken threads which form a matted
web. Broken kernels are preferred by this species.

Almond Moth. The almond moth, Ephestia cautella (Walk.),
is a pest of nuts, dried fruits and other products including peanuts. The
adult has a wing expanse of about 34 inch. The fore wings are narrow,
especially at the base, grayish to yellowish in color with dark markings
which may appear as zigzag lines or suffused bands across the wings ; hind
wings are whitish (30). The larva is a whitish caterpillar which may be
tinged with pink and green; it is cylindrical and about 4 inch long when
fullgrown; dark dots in four pairs of rows give the body a striated ap-
pearance. The larvae spin silken webs which may appear as masses inter-
mingled with food and excrement. In 1911 peanuts were listed (30) as a
stored product attacked by larvae of the almond moth. Since then this
species has been found causing economic damage to peanuts in many
sections of the world. Almond moth has been reported (17) as very de-
structive in Georgia. Other reports include those for Senegal (131),
Spain (134), Gold Coast (33) and Britain (62).

Saw-toothed Grain Beetle. Both larvae and adults of the saw-toothed
grain beetle, Oryzaephilus surinamensis (L.), attack peanuts and prod-
ucts derived from them. Bissel and DuPree (17), found this insect to be
the most abundant species'® in shelled peanuts in Georgia; Popenoe
(121) listed it third in importance among stored peanut pests. It is
recorded infesting peanuts in other parts of the world (10, 130). The
adult saw-toothed beetle is about 1/10 inch long and brownish in color;
the thorax bears 6 saw-tooth-like projections on each side. The whitish
larva has a brown head, is small, slender, and slightly longer than the
adult. Adults of the saw-toothed grain beetle have been kept alive over 3
years ; the average life is 6 to 10 months. Two related species, O. bicornis
(Er.) and O. mercator (Fauv.) occur in this country. The latter species
is known to infest peanuts in Senegal (131). Both have feeding habits
similar to that of O. surinamensis.

Flour Beetles. At least two species of flour beetles of the Genus
Tribolium attack stored peanuts and products derived from them. The
red flour beetle, 7. castaneum (Hbst.), and confused flour beetle, T.
confusum Duv., were fairly numerous in shelled peanuts (17). The
former species has been considered (121) as second in importance among

1% Also called fig moth.
16 Other than psocids.

INSECT PESTS 247

stored peanut pests in the United States. The two forms have been
recorded in peanuts from other parts of the world (Roubaud, (131), T.
castaneum and confusum in Senegal; Jarvis, (83), T. castaneum in
Australia; Fletcher, (57) and Roepke, (130), Tribolium sp. in Pusa
and Java; Okuni, (110), T. castaneum in Formosa). The flour beetles
are elongate, reddish-brown insects about 1/7 inch long. The larvae are
brownish white and somewhat flattened in appearance. Adults of the two
species may be distinguished by the following differences:

As viewed from the underside of the head, the eyes of the confused flour beetle
are separated by about three times the width of either eye, whereas the width of
each eye as seen from below in the red flour beetle is about equal to the distance
between them. The confused flour beetle has antennae gradually enlarged toward
the tip, the red flour beetle suddenly enlarged at the tip; the margin of the head

is notched at the eyes in the confused flour beetle and not so notched in other species.
(101).

Adult flour beetles may live 2 years or more, but the average life
is about 1 year (11).

Cadelle. The cadelle beetle, Tenebroides mauritanicus (L.), appears
to be of importance in peanuts, although literature references to infesta-
tions are scarce. It has been listed (121) as fourth in importance among
stored peanut pests, and has been found to be one of the more common
forms in shelled. peanuts stored in jute bags (17). Roubaud (131) re-
ported it infesting stored peanuts in Senegal. The adult is an oblong, flat-
tened beetle, black in color and measuring about 1/3 inch in length. The
larva is dirty-white with the head, thoracic shield, and two horny points at
the tip of the abdomen black; it is about 34 inch long when full-grown.
This insect is primarily a pest of grain and flour mills. The larvae some-
times bore into wood. Average life of the adult is 1 to 2 years. The extent
of its damage to peanuts needs further investigation.

Dermestids. Several species of dermestids infest peanuts. Among the
forms recorded in the literature are Trogoderma bicolor Arrow in peanuts
imported into Holland (24) ; Dermestes lardarius L. in peanuts in Europe
(173) ; Attagenus gloriosae imported into Holland (not established) in
peanuts (74); unidentified species of dermestids common in shelled
peanuts stored in jute bags in Georgia (17). The dermestids are small
beetles that are for the most part scavengers, feeding upon animal matter.
Forms that feed on plant products probably supplement the diet with
dead bodies of other insects (11). Thus, it would appear that the

248 THE PEANUT—THE UNPREDICTABLE LEGUME

principal damage to peanuts by these pests might be spoilage of products
intended for the edible trade.

Other Pests of Stored Peanuts. The Mediterranean flour moth,
Ephestia kuehniella Zell. may cause economic damage to peanuts. Larvae
of this species were considered by Popenoe (121) as sixth in importance
among stored peanut insects. However, the writer has found no ad-
ditional references to this insect infesting peanuts, although it is
distributed over many parts of the world.

Bruchids attack peanuts in storage, mostly in foreign countries.
Bruchus chinensis L. attacks peanuts in Java (129). Pachymerus acaciae
Gyll. is reported (40) as infesting peanuts and as having spread from
Asia to Greece, Italy and the north and west Coasts of Africa. This
species is recorded as attacking stored peanuts in Senegal (26) with
59,000 tons of peanuts being destroyed by it (145). Howard (79) referred
in a general way to fumigation as a means of protecting peanuts against
pea and bean weevils. However, this is the only reference found indicating
bruchid injury to peanuts in the United States and it is concluded that
such damage is not common.

The flat grain beetle, Laemophloeus minutus (Oliv.), a sap beetle,
Carpophilus sp., the cigarette beetle, Lasioderma serricorne (F) and
numerous psosids were found (17) in stored peanuts in Georgia and
were suspected of being injurious. Other reports include a sap beetle,
Carpophilus sp., in peanuts in Australia (83); a relative of cigarette
beetle, Lasioderma testaceum in peanut cake in Pusa; sap beetles, C.
ligneus Murr., C. hemipterus L., and C. decipens, attacking peanuts in
Europe (172) and C. obsoletus in Japan (75). All of these insects are
cosmopolitan in distribution. With the exception of the cigarette beetle,
they are probably incapable of damaging sound peanut kernels but may
thrive in peanuts already damaged by other insects or in certain products
derived from peanuts.

Five hundred tons of peanuts, imported into California from China,
were reported as destroyed by Aphomia gularis Zell. of the family
Galleridae (43). This species closely resembles Mediterranean flour
moth.

Additional reports of infestation in peanuts include the following:
Tobacco (currant) moth, Ephestia elutella (Hbn.), injuring peanuts in
Zomba (99), infesting peanut cake in Senegal (84) and in France
(85), and infesting peanuts imported into California from China (44) ;
Sitophilus oryza (L.) in shelled peanuts in Fiji (90) and in Georgia
(17); Alphitobius diaperinus (Panz.), A. piceus Ol, and Corcyra

INSECT PESTS 249

cephalonica Staint. in Senegal (131) ; Homoeosoma vagella Z. in Aus-
tralia; Embia (Monotylota) vayssierei Navas in stored peanuts in Sene-
gal (123); Sitotroga cerealella (Oliv.), Angoumois grain moth, and
Tenebrio sp., (meal worm) in stored peanuts in the United States (17).

Control. Natural enemies are of value in controlling pests of stored
peanuts, but the species of hosts and parasites involved are so numerous
and varied that a detailed discussion here is not feasible. Among the
more important parasitic and predaceous forms are Microbracon hebetor
(Say), M. jugeandis Ashm., Idechthis canescens (Grav.), Omorgus
frumentarius Rond., and Scenopinus fenestralis (L.) (136, 11).

Sanitation and proper bagging have been found helpful in preventing
insect damage to stored peanuts. Bissell and DuPree (17) found that
peanuts could be protected from serious infestation by storing them im-
mediately after shelling in cotton bags made from heavy material having
60 threads by 104 threads per inch. Jute bags counting 11 or 12 threads
per inch did not give satisfactory protection. For maximum protection,
properly bagged peanuts should be stored in clean, insect-free bins. To
free bins, storehouses, boxcars and the like of insects, the walls, floors
and ceilings may be sprayed with DDT ina 5 percent solution in light oil
(36, 37) or in the form of a 5 percent emulsion in water.

Heat and cold have been employed satisfactorily in preventing insect
damage to peanuts and peanut products in storage. It was found (19)
that a temperature of 125° F. for 6 hours destroyed insects in loose piles
of dry peanuts without injury to the peanuts. Also it was reported (36)
that a temperature of 120° to 130° F. maintained in all parts of flour mills
for 10 to 12 hours destroyed all insect life. Forced circulation of air was
necessary to maintain proper temperature throughout the treated area.
The use of heat is limited by facilities for maintaining suitable tempera-
tures within masses of stored products. Refrigeration is also effective
in preventing insect damage. Protection against insect infestations has
been reported when peanuts and peanut products are stored at 50° F.
or below (164). The keeping qualities of the products were also enhanced. .

Fumigation is perhaps the most feasible method of destroying insects
in stored peanuts, once they are infested. Materials which have been used
for this purpose include carbon disulfide and hydrogen cyanide (19, 33),
a mixture consisting of three parts ethylene dichloride and one part
carbon tetrachloride (80), ethylene oxide, 4 ounces plus 2.8 pounds of
carbon dioxide per 100 cubic feet in a vacuum tank filled with peanuts
(34), and methyl bromide (97, 139). Chloropicrin has been found effec-
tive, but it is absorbed and increases the acid content of the peanuts as

250 THE PEANUT—THE UNPREDICTABLE LEGUME

much as 300 percent (40) ; absorption may be reduced by using carbon
dioxide with a smaller dose of chloropicrin (34).

Of the several fumigants in common usage, methyl bromide is prob-
ably the most desirable for fumigating peanuts and peanut products,
provided tight masonry storehouses, vaults or fumigation chambers are
available. This gas is noninflammable, is highly toxic to insects, and
‘penetrates well into bagged commodities or other masses of stored prod-
ucts. It is highly toxic to warm-blooded animals and is almost odorless.
Well-trained personnel are required for fumigation with methyl bromide.
The gas is usually introduced through pipes or tubes from cylinders of
the liquid material, placed outside. The rate of application is 1 to 1%
pounds per 1,000 cubic feet where masses of stored products must be
penetrated. After an exposure of approximately 24 hours, the chamber
should be ventilated. In general, metal and wooden buildings are not suit-
able for fumigation with this material. For additional information on the
use of methyl bromide, the reader is referred to the Supplement to
USDA Circular 390 (39) and to USDA Circular 720 (37).

Stored peanuts in tightly constructed metal or wooden buildings may
be fumigated with a grain fumigant containing three parts ethylene
dichloride and one part carbon tetrachloride, applied at the rate of 4 to
5 gallons per 1,000 bushels of stored product (35).

A considerable amount of the information on control of insects in
stored peanuts was developed by research on these pests in other products.
Additional research is needed, particularly on the effect of fumigants,
refrigeration and heat treatment on peanuts and peanut products as well
as the insects involved.

Miscellaneous Pests

In addition to the insects discussed in this paper, numerous minor
pests have been observed attacking peanuts in various parts of the world.
No attempt is made to cover all of these pests, and no claim is made that
the publication is in any sense complete.

SELECTED REFERENCES

(1) AckKERmMAN, A. J. AND IsELY, Dwicut.
1931, THE LEAFHOPPERS ATTACKING APPLE IN THE OZARKS. U. S. Dept. Agr.
Tech. Bul. 263, 40 pp.
(2) ANDERSON, W. H.
1938. A KEY TO SEPARATE THE LARVA OF THE WHITE-FRINGED BEETLE,
Naupactus leucoloma BOH., FROM THE LARVAE OF CLOSELY RELATFD
species, U. S. Dept. Agr. Bur. Ent. and Plant Quarantine. E-422,

3 pp.

INSECT PESTS 251

(3) ANDERson, L. D. AND WaLxer, H. G.
1940. NOTES ON THE CONTROL OF ONION THRIPS. Jour. Econ. Ent. 33 (2):
278-280.
(4) ArRAnT, F. S.
1929, BIOLOGY AND CONTROL OF THE SOUTHERN CORN ROOTWORM. Ala. Agr.
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OF SEPT. TO DEC. 1921. Mo, Bul. Calif. Dept. Agr. 11 (1 and 4).

1940. RPT, CHIEF BUR. ENT. AND PLANT QUARANTINE FOR 1938-39. U. S.
Dept. Agr., 117 pp.
Swain, R. B.
1943, NEMATODE PARASITES OF THE WHITE-FRINGED BEETLES. Jour. Econ.
Ent. 36 (5):671-673.

1945. THE ASSOCIATION OF NEMATODES OF THE Genus Diplogaster WITH
WHITE-FRINGED BEETLES. Jour. Econ. Ent. 38 (4) :488-490.
SWEETMAN, H, L.
1926. RESULTS OF LIFE HISTORY STUDIES OF Diabrotica 12-punctata FABR.
(CHRYSOMELIDAE, COLEOPTERA). Jour. Econ. Ent. 19 (3) :484-490.
VAYSSIERE, P.
1939, AU SUJET DE L’ORGANISATION DE LA LUTTE CONTRE LES INSECTES
NUISIBLES AU SENEGAL ET AU SOUDAN. Act. Ass. Col. Sci. 15 (166-
167) :45-52, 65-70.
VicKERY, R. A.
1929. sTUDIES ON THE FALL ARMY WORM IN THE GULF COAST DISTRICT OF
Texas. U.S. Dept. Agr. Tech. Bul. 138.
Wa ttace_, C. R.
1940. ON THE OCCURRENCE OF THE WEEVIL Naupactus leucoloma BOH. IN
AUSTRALIA. Jour. Aust. Inst. Agr. Sci. 6 (4):209-211.
Watson, J. R.
1916. LIFE HISTORY OF THE VELVETBEAN CATERPILLAR (Anticarsia gemmatilis
HUBNER). Jour. Econ. Ent. 9 (6) :521-528.

1918. Report of the Department of Entomology, Fla. Agr. Expt. Sta. Rpt.
for Fiscal Year Ending 30th June 1917.

1918. THYSANOPTERA OF’FLORIDA. Florida Buggist 1 (4) and 2 (1): 53-77.

1922a, REPORT OF ENTOMOLOGIST. Fla. Agr. Expt. Sta. Rpt. 1921-1922.
pp. 56-59.

1922b,. THE FLOWER THRIPS. Fla. Agr. Expt. Sta. Bul. 162:27-51.

1930. Report of the Department of Entomology, Fla. Agr. Expt. Sta. Rpt.
for Fiscal Year Ending June 30, 1930. p. 67.

a
260 THE PEANUT—THE UNPREDICTABLE LEGUME

(154) Watson, J. R.
1937a. Naupactus leucoloma (COLEOPTERA, CURCULIONIDAE), A PEST NEW
TO THE UNITED STATES. Fla. Ent. 20 (1):1-3.

(155)
1937b. ADDITIONAL NOTES ON NAUPACTUS LEUCOLOMA. Fla. Ent. 20 (2):
22-25.
(156) Warts, J. G.
1934. A COMPARISON OF THE LIFE CYCLES OF Frankliniella tritica (FITCH),
: F. fusca (HINDS) and Thrips tabaci LIND. (THYSANOPTERA-THRIPIDAE)
IN SOUTH CAROLINA. Jour. Econ. Ent. 27 (6): 1158-1159.

(157)
1936. A SURVEY OF THE BIOLOGY OF THE FLOWER THRIPS Frankliniella tritici
(FITCH) WITH SPECIAL REFERENCE TO COTTON. S. C. Agr. Expt. Sta.
Bul. 306, 46 pp.
(158)

1938. SPECIES OF THRIPS FOUND ON COTTON IN SOUTH CAROLINA. Jour. Econ.
Ent. 30 (6) :857-860.
(159) Wess, H. B.
1918, THE CONTROL OF IMPORTED PESTS RECENTLY FOUND IN NEW JERSEY.
Jour. Econ. Ent. 11 (1):122-125,
(160) Witson, Coyt AND AraAnrt, F. S.
1949, CONTROL OF INSECTS AND DISEASES OF PEANUTS. Ala. Agr. Expt. Sta.
Leaflet 27.
(161) Witson, J. P. AND Arant, F. S,
1947. STATUS OF PEANUT-WORM CONTROL. Ala. Agr. Expt. Sta. Mimeogr.
Leaflet.
(162) WinBurRN, T. F. AND PAINTER, R. H.
1932. INSECT ENEMIES OF THE CORN EARWORM. Jour. Kan. Ent. Soc. 5 (1).
(163) WisEcup, C. B. anp Haystip, N. C.
1943. CONTROL OF MOLE CRICKETS BY USE OF POISONED BaITs. U. S. Dept.
Agr. Leaflet 237, 6 pp.
(164) Wooproor, J. G., THompson, HELEN H. anp CEcIL, 5. R.
1947, REFRIGERATION OF PEANUTS AND PEANUT PRODUCTS. Refrigerating
Engineering 53 (2):124.
(165) Youne, H. C.
1944, DDT AGAINST THE WHITE-FRINGED BEETLE AND VELVETBEAN CATER-
PILLAR. Jour. Econ. Ent. 37 (1):145-147.

(166)
1945. INSECTORY AND FIELD-CAGE TESTS WITH DDT AGAINST WHITE-FRINGED
BEETLE ADULTS CONDUCTED AT FLORALA, ALABAMA, DURING 1944,
U. S. Dept. Agr. Bur. Ent. and Plant Quarantine. E-662, 4 pp.
(167)
1946. Ann. Prog. Rpt. Florala, Ala., White-Fringed Beetle Sta. U. S. Dept.
Agr. Bur. Ent. and Plant Quarantine in Coop. with State Agencies
of Fla., Miss., Ala. and La.
(168)

1947, Ann. Prog. Rpt. Florala, Ala., White-Fringed Beetle Sta. U. S. Dept.
Agr. Bur. Ent. and Plant Quarantine in Coop. with State Agencies
of Fla., Miss., Ala. and La.

INSECT PESTS 261

(169) Younc, H. C. anp App, B. A.
1939. BIOLOGY OF THE WHITE-FRINGED BEETLE Naupactus Leucoloma BOR.
U.S. Dept. Agr. Bur. Ent. and Plant Quarantine E-464,
(170) AND GREEN, G. D.
1938. THE WHITE-FRINGED BEETLE, Naupactus leucoloma Bou. U. S. Dept.
Agr. Bur. Ent. and Plant Quarantine. E-420, 14 pp.
AND GILL, J. B.
1948. SOIL TREATMENTS WITH DDT TO CONTROL THE WHITE-FRINGED BEETLE.
U.S. Dept. Agr. Bur. of Ent. and Plant Quarantine. E-750.
(172) ZacueEr, F,
1929, EIN FUR DEUTSCHLAND NEUER SCHLADING AN BACKOBST Carpophilus
ligneus MURR, UND ANDERE SAFTKAFER; C. ligneus, A PEST OF DRIED
FRUIT NEW TO GERMANY AND OTHER NITIDULID BEETLES. Mitt. Ges.
Vorratsschutz 5 (1):2-5.

(171)

(173)
1932, INTERESSANTE FAELLE DES SCHADLINGSAUFTRETENS AN NAHRUNGSUND
GENUSSMITTELN, WEBWAREN UND BAUSTOFFEN. Mitt. Ges. Vor-

ratsschutz 8 (4):42-48.

CHAPTER VIII

PEANUT DISEASES

KENNETH H. GARREN* AND COYT WILSON*

In the early years of its cultivation, the peanut was considered some-
what disease resistant. In 1895, after peanuts had been an important crop
for a half century, a bulletin (55) on peanuts, published by the U. S.
Department of Agriculture, made no specific mention of diseases. Re-
visions of this bulletin, dated 1909 and 1917, described peanuts as re-
‘markably free from disease. Leafspot was mentioned but damage was
regarded as unimportant except in low or poorly drained portions of
fields (15, 16).

As peanut production increased, diseases began to attract more at-
tention. There began, therefore, an Era of Exploration. During this
period numerous peanut diseases were observed and recorded, many of
which never appeared again in the literature. The next era was notable
for concentrated study of a few diseases of outstanding local importance.
Among such diseases were: Bacterial wilt in the East Indies, rosette in
Africa, and leafspot in the southern United States. Overlapping this
Concentrated Era was a fourth or General Era which resulted in the
publication of reviews of peanut diseases, either from a world-wide (86)
or strictly localized viewpoint (64, 98, 99).

At the present time interest in and the study of peanut diseases appear
to be in this general phase. During the years 1941 to 1945 the acute
shortage of vegetable oils focused attention on peanut culture in the
United States and numerous surveys of peanut diseases were made. As a
result of these surveys there developed the concept that many diseases
other than the obvious ones are found in peanut fields, and that, while the
damage caused may be considerable (125), it is difficult to estimate the
specific damage to be attributed to individual diseases.

1 Kenneth H. Garren, formerly associate botanist, Georgia Agricultural Experiment Station,
is associate professor of botany and plant pathology, Alabama Polytechnic Institute; Coyt Wilson
is plant pathologist at the same institution.

262

PEANUT DISEASES 263

PEANUT DisEAsEs OF MAjor IMPORTANCE
IN THE UNITED STATES ©

DISEASES AFFECTING STAND ESTABLISHMENT

Spotty stands of peanuts are common in the southeastern United
States (124) and other peanut-producing regions (43, 64). Since pro-
duction costs per ton are largely a function of area cultivated, these poor
stands are important considerations in the economics of peanut produc-
tion.

Several things may account for spotty stands. The principal causes
appear to be: (A) Poor seed stocks (old seeds, improperly stored seeds,
seeds with fungus damage or mechanical injury, etc.). (B) Over-stretch-
ing of seed supply or improper spacing of seeds. (C) Inferior planting
equipment. (D) Unfavorable conditions after planting. (E) Depreda-
tions of field mice, birds, and other animals. (F) Seed rots and seedling
blights.

Consideration of these items shows that disease is not the sole
factor causing poor stands.

A number of distinct diseases affect peanuts early in the growing
season. When considered individually, many of these diseases do not ap-
pear to be of importance. Collectively, however, they often are serious.
Of these, the pre-emergence diseases probably have the most direct effect
on stand establishment in the southeastern United States (163).

Pre-Emergence Diseases

Importance. Soil rot of seeds is regarded as one of the three most im-
portant peanut diseases in Rhodesia (64). Its importance in the southern
United States must be obtained indirectly, primarily from the emphasis
placed on control programs in recent years. The most concrete evidence
may be obtained from reports of increased emergence of 15, 25 or up to
40 percent following such control programs (43, 45, 46, 103).

Description. Planted seeds and very young plants are subject to two
types of diseases before emergence. The entire seed may be decayed, or
the developing embryo of young plant may be attacked by saprophytic
fungi, or damping-off fungi. Both of these types of pre-emergence dis-
eases have been reported on peanuts (43, 102, 105).

Organisms. The organisms associated with pre-emergence diseases
have not been studied extensively. Soil-borne parasitic and saprophytic
fungi may decay seeds, particularly if germination is delayed or if the seed

264 THE PEANUT—THE UNPREDICTABLE LEGUME

is damaged. In addition to these soil fungi a fungus flora becomes associ-
ated with the peanut fruit as it develops in the soil (162), is present at
harvesting (48, 114), and is still present in or on fruits and seeds after
storage (41, 67, 111, 149). The majority of species of this fungus flora are
saprophytes such as Aspergillus spp., Rhizopus spp., Penicillium spp.,
and Fusaria, but some are definitely parasites such as Pythium spp.
(111), Sclerotium rolfsit Sacc. (149), and parasitic Fusaria (41).

Control. Losses from pre-emergence diseases of peanuts may be sig-
nificantly reduced by seed treatments (45, 46, 51, 64, 103, 105, 155),
though in a few instances seed treatment for peanuts has not been con-
sidered worthwhile (67, 76, 151). Properly applied seed fungicides will
be effective against seed-borne saprophytes and parasites, and if germina-
tion is not unduly delayed by adverse weather conditions these fungicides
will also be effective against soil-borne fungi (105). Most of the beneficial
results of seed treatment of peanuts is due to prevention of decay prior
to germination (102, 163).

Increases in emergences from machine-shelled seeds of 25 percent or
more are not unusual following seed treatment, and it has been estimated
that North Carolina farmers save around $125,000 annually by using
treated machine-shelled seeds in preference to hand-shelled seeds (103).
Table 1 gives some comparative emergences for treated and untreated
machine-shelled seeds as selected from various reports.

There are several factors that vary the effectiveness of peanut seed
treatment. The most important of these factors are:

Table 1.—RESULTS OF SEED TREATMENT TESTS ON PEANUTS

Emergence from
Location Type of Year Machine-shelled seeds | Bibliog-
of test seed used of test raphy
Untreated | Treated reference
Percent Percent
North Carolina...... Runner "43 54 75 (105)
North Carolina......| Runner "46 50 60-70 (46)
North Carolina...... Va. Bunch *42 39 61 (124)
North Carolina..... Spanish "42 57 72 (124)
Virginia............ Runner "45 66 84 (45)
Virginia............ Jumbo "46 85 96 (46)
South Carolina...... Spanish *45 77 94 (45)
South Carolina...... Spanish "46 54 85 (46)
Georgia............ Spanish "45 53 80 (45)
Alabama........... Runner 46 45 95 (46)
Alabama........... Runner 4 yr. ave. 54 73-88 (163)
Alabama........... Spanish "46 43 69 (46)
Alabama........... Spanish 4 yr. ave. 50 79 (163)

PEANUT DISEASES 265

(a) Type and quality of seed stocks: No amount of seed treatment
will change poor seed into good seed. Although not recommended, “pegs”
(shriveled, under-developed seeds) are still widely used as seed stocks.
The comparative effectiveness of seed treatment on plump and shriveled
seeds has been studied (46), and the results indicate that emergence
from plump seeds is always considerably higher than that from shriveled
seeds. When seeds are stored under conditions detrimental to quality,
any subsequent séed treatment will be less effective. Seed treatment,
therefore, is not a corrective for improper storage.

(b) The use of unshelled seed. Usually there is no appreciable in-
crease in emergence as a result of treatment of unshelled seeds (103, 124,
155, 163). Pre-soaking Spanish peanut pods in water increases the sub-
sequent germination of unshelled seeds (67, 103, 124), but treatment of
pre-soaked pods gives no additional increase in germination (103).
Germination of pre-soaked unshelled Spanish peanut seeds usually is
less than that of treated- machine- or hand-shelled seeds (103).

(c) Method of shelling. Injury by machine-shelling provides points
of entry for soil fungi, and emergence from untreated hand-shelled seeds
is much better than that from untreated machine-shelled seeds. Treating
hand-shelled seeds generally increases emergence, but the proportion
of increase is not as great as from treatment of machine-shelled seeds.
Emergences from treated machine-shelled seeds compare favorably with
emergences from untreated hand-shelled seeds (50, 105, 163).

(d) Material used. The most apparent factor which can influence the
effectiveness of seed treatment is the chemical itself. Numerous fungicides
are designed exclusively for seed treatment. Three of these fungicides,
Arasan (50 percent tetramethyl thiuramdisulfide), 2 percent Ceresan
(2 percent ethyl mercury chloride), and Spergon (98 percent tetrachloro-
parabenzoquinone), have been tested so frequently that their effectiveness
is definitely established. The majority of reports show Arasan and 2 per-
cent Ceresan about equal, with Spergon less effective but still very benefi-
cial (45, 46, 50, 51, 53, 153, 155, 163, 167). Other newly introduced seed
fungicides have been tested and some give excellent promise. Extensive
testing should soon give definite evaluations for these newer seed fungi-
cides.

(e) Methods. The method of applying seed fungicides influences
effectiveness of the treatment. A light film of the material on every seed
is desired. Higher rates of application do not give additional increases in
emergence (103), and over-dosage with mecurial treatments results in
abnormal germination and seedling death (67, 163). There are, un-

266 THE PEANUT—THE UNPREDICTABLE LEGUME

doubtedly, many cases of apparent ineffectiveness of seed treatment due
to poor application of the material used. Slurry treatments have not come
into use on peanuts.

(f) Times of shelling, treatment and planting. Peanuts shelled and
treated up to 3 months or longer before planting produce stands as good
as those produced by seeds shelled and treated immediately before plant-
ing (51, 103, 163). It appears, therefore, that within reasonable limits
the time elapsing between shelling and treatment and subsequent planting
does not alter the effectiveness of seed treatment if the seeds are properly
stored throughout. Treatments are equally effective if applied at the time
of shelling or just before planting.

(g) Environmental conditions after planting. Most of the benefits of
seed treatment for peanuts appear to arise from prevention of decay of
seeds prior to germination (102, 163). Rains which wash off chemicals
before germination will decrease the effectiveness of seed treatment (67).
Even in comparatively dry soil there will be a gradual dissipation of the
chemicals, thus any environmental condition inhibiting or slowing down
germination will reduce the effectiveness of treatment.

To summarize: The existing evidence shows that pre-emergence
diseases of peanuts are effectively controlled by seed treatment. Factors
which influence the effectiveness of seed treatment, however, make the
following precautions necessary :

1. Use only high quality seeds which have been stored properly.
2. Use machine-shelled seeds in preference to unshelled seeds.
3. Use a recommended seed fungicide.
4. Follow directions for treatment and avoid injury from over-treat-
ment or failure from under-treatment.
. Apply chemicals to seeds in a manner which gives even coating of
every seed.
6. Choose the most convenient time for shelling and treatment, but
keep within reasonable limits.
7. Consider environmental conditions and try to plant under con-
ditions promoting rapid germination.

Post-Emergence Damping-O ff

Importance. Typical damping-off causes slight losses every season in
the southeastern United States. There are, however, no reports of damp-
ing-off as an important disease in any peanut-producing region. Reports
of surveys of peanut fields for diseases contain only occasional references

PEANUT DISEASES 267

to typical damping-off fungi. When such fungi are mentioned they are
given a relatively minor position (97, 123).

Control. Damping-off must be regarded as a minor factor contributing
to poor stands of peanuts. The use of treated seeds and close spacing to
insure replacements for plants killed by damping-off constitute the only
recommended control measures at present. The general prevalence of
such practices probably accounts for the infréquency with which damping-
off is observed.

Seedling Dry Rots

Importance. Young peanut seedlings are subject to a type of rot
distinct from damping-off and known as “dry rot” (63). The fungi ap-
parently associated with most seedling dry rots in southeastern United
States are Sclerotium bataticola Taub. (the “charcoal rot” organism)
and Rhizoctonia solani Kuhn. Reports on peanut diseases have shown that
these fungi are widespread in the United States (77, 78, 87, 101, 111,
119, 123, 126, 157) and elsewhere (26, 115, 147, 152). In North Caro-
lina each of these organisms accounted for about 35 percent of the total
isolations from diseased peanut tissue (101). S. bataticola has been called
“a major pathological and economic problem” on various crops including
peanuts in southern United States (63), and reports on peanuts from
India (147, 152) and Palestine (115) have similarly evaluated this
organism. There are possibly other types of seedling dry rots as yet not
recognized as distinct. For example, an early stage of Fusarium wilt?
reported from the southeastern United States (74, 92) and other regions
(80, 115) may sometimes be confused with seedling dry rots.

Most reports do not distinguish between seedling dry rots and the
attacks of the same causal organisms on more mature plants. It has been
noted that S. bataticola attacks peanuts principally in the seedling stage
(63, 152) but some observations may have been of the “ashy stem blight”’
on mature plants.? Observations in southeastern United States tend to
indicate that R. solani rarely infects mature peanut plants? and then
generally affects only single branches, but some of these reports may
have included attacks on mature plants. On this basis, therefore, seedling
dry rots are best regarded as of intermediate importance in relation to de-
velopment of peanut stands.

Description. Charcoal rot is easily recognized. The first symptoms
are greenish-grey watery necrotic areas on stems just at the soil surface.

2 See page 303 for discussion of Fusarium wilt. | ;
3 See page 305 for discussion of “‘ashy stem blight,” and R. solani on mature peanut plants.

268 THE PEANUT—THE UNPREDICTABLE LEGUME

As the water-soaked appearance disappears the necrotic areas become
a dull, dry brown due to formation of sclerotia of S. bataticola. As lesions
develop the number of sclerotia increases and the base of the stem looks
very much like charcoal. Rarely does the water-soaked appearance persist
to the charcoal stage. Usually the entire plant wilts and dies but numerous
instances of complete recovery from charcoal rot have been observed.
When the lesion remains small, the plant is somewhat stunted and the
stem is easily broken by wind or cultivation. The necrotic areas and
lesions usually extend below the soil surface for a considerable distance.

Rhizoctonia dry rot of peanut seedlings is typical of the effects of this
organism on plants. The first evidence is usually a faint yellowish streak
on the stem at the soil line. This streak enlarges, becomes necrotic, and
develops into a definite light-brown, dry crack-like lesion. When infection
spreads around the succulent stem the top wilts and dies. Sometimes the
unwilted tops break off at the lesions. The lesions usually do not extend
very far below the soil line. Peanut plants frequently survive seedling in-
fection by R. solani.

Organisms and pathogenicity. The parasitism of Sclerotium bataticola
has been studied with a number of plants. As once summarized (63) it
appears that S. bataticola is “moderately and variably aggressive. Its in-
vasion is favored by devitalization, characteristic of plants subjected
to environmental extremes of continental climates, and wounds or attacks
of other organisms. It is adapted to high temperatures.” Inoculation tests
show that S. bataticola can infect and kill peanut seedlings at fairly high
temperatures but not at low temperatures (111).

The parasitism of FR. solani has been established by studies on many
crop plants. Inoculation tests show that R. solani produces dry-rot of
peanut seedlings identical with that found in the field. R. solani grows
readily from field dry-rotted peanut seedlings in moist chambers though
it is sometimes difficult to obtain the organism by the usual methods of
isolation.

Although differences in susceptibility of peanuts to infection by R.
solani have been reported (147), no resistant varieties have been sug-
gested. Twenty peanut varieties have been tested for susceptibility to
S. bataticola and no resistance was noted though peanuts grown under
irrigation and shallow cultivation were attacked more frequently than
those grown in dry soil with deep cultivation (147).

Control. Both S. bataticola and R. solani can be seedborne (41, 48,
147). A high percentage of infection by R. solani is sometimes attributed
to seed-borne inoculum (147), but it probably is less frequently seed-

PEANUT DISEASES 269

borne than is S. bataticola. Seed treatment should be effective against
most of the seed-borne inoculum. Since these organisms are universally
established in peanut soils, seed-borne inoculum may be a minor source
of infection. Seed treatment may be effective against a considerable por-
tion of the soil-borne inoculum, particularly in the case of S. bataticola,
which frequently infects seedlings through cotyledons. Close spacing of
seeds to insure replacements is also to be recommended.

Collar Rot*

Importance. In the southeastern United States peanuts are subject
to a stem and root rot which developed later than damping-off and seed-
ling dry-rots, and features otherwise distinct. The name “collar rot” is
proposed for this disease. Apparently such rots have been noted in the
southeastern United States for some time (97, 101, 111) and previous
reports have indicated that the problem is a complex one (101, 111).

Collar rot was serious in several Georgia counties in 1946 and 1947.
In 1946 the entire stand was so depleted in a 10-acre field that replanting
was necessary. A similar situation was reported from Texas in 1941
(74). Serious depletions of experimental stands were observed in 1947 in
Georgia, and depletions of farmers’ fields of runner peanuts were noted
in Alabama in 1947 and 19485. A few references in the literature indi-
cate, indirectly, that an early root-rot disease is prevalent in other States
(74, 101, 111, 123) and the crown rot of peanuts described from Aus-
tralia (99, 100) bears many points of resemblance to collar rot.

Description. Peanuts succumb to collar rot from emergence to early
flowering. The disease, however, seems most prevalent from 20 to 40
days after planting. When plants are attacked shortly after emergence,
hypocotyls are killed and there are black necrotic areas on cotyledons
and plumules. In early stages the main axis of plants are wilted with
necrotic areas in the region of the cotyledons, but side branches and root
systems are unaffected. Frequently a good mat of adventitious roots has
been formed just below the cotyledons. Next, the main axis dies and the
necrosis spreads downward on the taproot. A few plants recover even
after the main axis is dead and the taproot badly rotted. Undoubtedly this
recovery is due to good development of adventitious roots. The majority
of plants attacked, however, either die or remain stunted. The advanced
stage is characterized by dead taproot systems and side branches dying or

4 Based primarily on observations made in Georgia and on unpublished data of the Georgia Ex-

eriment Station. . ;
5 5 Observations from unpublished data of the co-author, Coyt Wilson, Alabama Experiment

Station.

270

THE PEANUT—THE UNPREDICTABLE LEGUME

Table 2,—F unc! ISOLATED FROM PEANUTS WITH COLLAR Ror In GEorctA, 1945-19475

Fungus isolated

Comparative frequency

Pusariiin SpPpin diss. ¢aecastinys eagleawesn den redeieanes 4
Di plodta: Spin ve eri isd we eek oa yok aS As haw OED LEG OD AAS ED
PenrCulium SpPivdisigwv seca es ven yes cena ve be eas caaee ee
AS per gullies sp pics ssieg cers cacaes gd iain, aad ad bob eadkih Ra eonn sce dean Wea
TRRISO DUS SP os. 2. c5808 ia loctlre wields Cla a tele hd A 0 MUTED HORE
Sclerotium bataticola... 0... ccc ccc cece cet e nes
Rhizoctonia solant.. 0.6... ccc ccc cece eee etnies
Trichoderma: SPP os visaass aguas ghee yee ated PA He EEE OEEN SUES
Baeteriassassoes soe 2.8 Hb pee ae Ra wae ae Rood Fe Eo RE Bide Daa

Frequent
Frequent
Fairly frequent
Fairly frequent
Fairly frequent
Fairly frequent
Rare

Rare

living only when some adventitious roots have developed. In this stage,
the main axis and taproot are shredded and held together by a few sound
vascular bundles. The mass of dead tissue is usually dark reddish brown
and powdery.

Organisms and pathogenicity. The nature of early collar rot suggests
a fungous disease, and no evidence has been obtained which would con-
nect insects or grubs directly with the disease. Somewhat detailed isola-
tions of fungi from diseased plants have been made, and typically, a
variety of fungi was isolated with no agreement between seasons as to the
predominant fungus. Table 2 lists the comparative frequency 2 isolation
of several fungi from diseased plants in Georgia.

Similar results have been reported from North Carolina (101, 111).

Since a number of these fungi have been reported as pathogens on pea-
nuts (table 3), inoculation tests were run for 3 years at the Georgia Ex-

Table 3.—FUNGI ORDINARILY CONSIDERED SAPROPHYTES REPORTED AS PATHOGENIC
FOR PEANUTS

Patho- Patho- Bibliog-
Fungus Reported from genicity genicity raphy
: tested proved reference
Diplodia sp........ Southeastern United States’ No —_— (119)
Southeastern United States Yes No (92)
Southwestern United States No — (79)
Burma _ _ (149)
Penicillium spp... .|Uganda _ —_ (145)
Aspergillus sp...... East Indies Yes Yes (72)
Australia _ _— (99, 100)
Rhizopus sp........ Uganda = = (145)

8 Unpublished data, Georgia Experiment Station.

PEANUT DISEASES 271

periment Station, with fresh isolations of all fungi from collar-rotted pea-
nuts. In two tests one set of plants was wounded by tearing off cotyledons
and ripping through stems underneath the soil surface.

With the exception of R. solani there was no indication of patho-
genicity for any fungi or bacteria. Even the severely wounded plants de-
veloped to maturity after inoculation. Most plants inoculated with R.
solam died, but the necrosis was typical for R. solani infection and in no
way resembled collar rot as observed in the field. In 1948 with isolates of
fungi from collar rot of runner peanuts Wilson™ found some indication of
parasitism for Diplodia sp.

From inoculation tests no specific fungus can at present be connected
with collar rot of peanuts. There are, however, several possible explana-
tions for the disease, the most likely of which are: (A) The disease is
due to a fungus not yet isolated and identified; (B) the disease is due
either to R. solani, a parasitic Fusarium sp., or to a parasitic bacterium
and the true pathogen is obscured by a succession of saprophytic fungi ;
or (C) an involved complex operates in peanut fields in which mechanical
injury, chemical injury, insect and nematode injury, and “light” parasitic
infection all provide dead tissue in which ordinarily saprophytic fungi
thrive and eventually destroy living tissue. A similar complex has been
suggested as associated with a root rot of tobacco and small grains (70),
and it has been indicated that peanut root rot may, under different con-
ditions, result from a wide variety of fungi (111).

Control. Collar rot has been observed as frequently and to as great an
extent in fields planted with treated seeds as in those planted with un-
treated seeds. There have been instances in which injury from seed treat-
ment has been suspected as a factor in the development of the disease. At
present the only recommendations for control are: (A) Use of seed stocks
carefully selected to eliminate damaged or broken seeds; (B) use of care
in treatment of seeds to avoid injury from seed treatment; (C) close
spacing of seeds to insure good stands even if some plants are killed by
collar rot.

DISEASES OF THE GROWING SEASON

Cercospora Leafspot

Importance. Because of frequency of occurrence Cercospora leafspot
is generally regarded as one of the most important diseases, or perhaps
the most important disease of peanuts. Although it has received more at-

T Unpublished data, Alabama Experiment Station.

272 THE PEANUT—THE UNPREDICTABLE LEGUME

tention than any other disease of peanuts in the United States, there is
little agreement as to its relative destructiveness.

Obviously the defoliation greatly decreases the value of the vines for
hay, but as indicated by Miller (94) there are observers who feel that
leafspot does not result in appreciable reduction in yield of nuts. The
majority of observers, however, maintain that considerable loss in yield
of nuts results from the disease.

The best estimate of importance of peanut leafspot may be obtained
from results of studies on control. In Virginia 30 tests showed average
yields about 500 pounds per acre less in untreated fields than in fields in
which leafspot had been decreased by control measures (94). This indi-
cated a loss in yield of about 20 percent from leaf-spot infection. Interpret-
ing results of extensive tests in Georgia similarly (172) the nut-yield
loss from leafspot is indicated as from 20 to 25 percent.

Description. Two fairly distinct types of necrotic spotting are recog-
nized as common on peanuts in the southeastern United States, and each
has been connected with a specific Cercospora sp. (68, 171). The exist-
ence of two species of Cercospora associated with peanut leafspot was
clarified by Woodroof in 1932 (171). The effects produced by these
organisms, however, are still regarded as only one disease. Control
measures seem equally effective on both organisms. Peanut-breeding
programs, however, may produce varieties resistant to only one of the
pathogens (61), in which case it may be necessary to divide “peanut
leafspot” into two diseases.

Spotting associated with Cercospora arachidicola Hori (Mycosphae-
rella arachidicola Jenkins) appears earlier and becomes epiphytotic
earlier than does that associated with C. personata (B. and C.) E. and
E. (M. berkeleyii Jenkins). It seems logical, therefore, to designate them
“early leafspot” and “late leafspot.” There is a period of overlapping,
however, and frequently both types of spotting are found on the same
plant (171).

In the initial stages the two types of spotting are indistinguishable
(68). Spots appear as slightly pale or blanched-like areas and a break-
down of the lower epidermis is evident. The spots develop rapidly and
become distinctly yellow on the upper surface of the leaflet. With this a
necrosis develops from the center of the lesion, or the entire lesion may
become necrotic at one time.

Later stages in necrosis serve to distinguish between the two leaf-
‘spots (68). Early leafspot is characterized by a yellow halo of variable
width, while halos are found only with more mature spots of the late type.

PEANUT DISEASES 273

At maturity early leafspots are reddish-brown to black, and lighter brown
to tan with less distinct halos on the lower surface. Late leafspots are
soon very dark brown to almost black on both surfaces.

Cushions of conidiophores are formed at first only on the upper sur-
face in early leafspot, but sometimes form on the lower surfaces of older
spots. In late leafspot, however, conidiophores are almost always confined
to the lower leaf surfaces, and the cushions of tufts usually are in plainly
visible concentric circles. When the conidiophore cushion of late leafspot
becomes amphigenous with age, this concentric marking remains plainly
evident (68).

Both leafspots are distinctly necrotic at maturity. The spots are
circular, or irregular, and often coalescing. Sizes range from 1 mm. to
over 1 cm. in diameter (68). Spots on stems, petioles, pegs and pods are
similar, but more frequently are irregular or eliptical in shape. In early
leafspot the petioles and stem lesions develop later in the season than do
those on the leaves (171). These symptoms are shown in figure 1.

Apparently control measures so effectively prevent premature leaf
shedding (68, 171) that few observations have been made on defoliation

Courtesy Alabama Agricultural Experiment Station.

Figure 1—Cercospora leafspot on leaves of runner peanuts. The spots with the
halos on the leaf at the left are old lesions caused by Cercospora arachidicola.
The dark spots on the leaf at the right are young lesions caused by Cercospora
personata.

274 THE PEANUT—THE UNPREDICTABLE LEGUME

effects. The interrelationships between time of infection, severity of in-
fection, beginning of defoliation, and severity of defoliation have not been
extensively studied. In Georgia, leafspot appears sometimes in June on
peanuts planted in late April (172), and without control spotting in-
creases rapidly during July so that defoliation is noticeable by August. A
close relationship is observed to exist between the amount of leaf spotting
and the amount of defoliation (94).

Comparative studies (68, 171) have shown that late leafspot usually
appears 3 to 4 weeks later than early leafspot.

Organisms and pathogenicity. Woodroof (171) has clarified the
synonomy and nomenclature of the conidial stages of the peanut leafspot
organism. Her studies established Cercospora arachidicola Hori as the
correct name for the early leaf-spot organism, and C. personata (B. and
C.) E. and E. as the correct name for the late leafspot organism. Jenkins
(68) studied the development of both organisms and connected them
with Mycosphaerella perithecial stages which were found to develop only
on overwintered material.

The pathogenicity of both organisms has been proven (68). The first
infection is from ascospores formed on overwintered peanut debris.
There have been reports that the disease is seed-borne (94) but most ob-
servers feel that it is not. Following initial infection and an “incubation”
of 2 to 3 weeks (68) the lesions become evident and the organisms pro-
duce conidia in abundance. These conidia then spread infection rapidly.

There is a leafspot of the common coffee weed (Cassia tora L.) of
the southeastern United States caused by a Cercospora sp., but attempts
at cross inoculation. of this Cercospora sp. with peanuts have failed®.
Possibly other weeds are hosts of the peanut leaf-spot organism and thus
may serve as additional sources of ascospores for initial infection. As a
rule, however, there is more than enough peanut debris to provide an
abundance of initial inoculum.

The production of perithecia of the organisms on overwintering ma-
terial has been studied (68). It appears that even under ideal conditions
perithecia are formed sparingly. Rapid disintegration of the substratum
may be a factor in this, and temperature may be a limiting factor since
mature perithecia are not found in Georgia before June. Some rainfall
during the period of spermagonial discharge is also necessary. Asci al-
most always mature gradually so that ascospores are discharged over a
considerable period of time. Initial infections usually are scattered in the
southeastern United States (68), but peanut fields rarely, if ever, escape

8 Unpublished results, Georgia Experiment Station.

PEANUT DISEASES 275°

infection. Small spots of initial infection serve as the starting point from
which secondary infection spreads over almost unlimited areas.

Conidia are primarily windborne (94) and other means of dissemi-
nation are of little significance. Under ideal conditions conidia germinate
within 3 to 8 hours (68), The conidia do not germinate if completely cov-
ered by water, or if there is insufficient moisture. Infection takes place
through either surface of the leaflet, but most infection probably is
through the lower surfaces since they are not subject to rapid dessication.

Penetration of the germ tube is through epidermis or stomata. Cer-
cospora arachidicola has intercellular mycelium but no haustoria. Host
cells die rapidly in advance of the mycelium, and the hyphae penetrate
the dead cells. Mycelium of Cercospora personata leafspot organism re-
mains intercellular with branched or botryose haustoria which may be
found in apparently normal cells.

The early leaf-spot organism develops consistently but the late leaf-
spot organism is sporadic, being widespread some years, and again rarely
found or entirely missing. It appears that, when occurring, the late leaf-
spot organism causes a more rapid defoliation (68, 171). The regular
occurrence of early leafspot and harvesting of many peanuts before late
leafspot reaches epiphytotic proportions indicate that in lower southeast-
ern United States early leafspot is more destructive. In this region early
leafspot usually becomes epiphytotic in August ; late leafspot sometime in
September (68).

Factors influencing the severity and spread of infection by leaf-spot
organism have been studied and discussed (94). Various fertilizer pro-
grams have no apparent effect on the disease. Age of plants, rate of early
growth, method of weed control, and frequency of rainfall appear to be
influencing factors. Infection is usually more severe on peanuts following
peanuts every year or every other year than when 3-year rotations are
practiced.

Control. Field sanitation can offer no great hope for control of peanut
leafspot. Resistance has been reported sporadically, but at present no
definite resistance exists in any standard variety of peanuts. The possi-
bilities along this line have been discussed by Higgins (61, 62) who noted
an apparently independent inheritance of resistance to the two types of
leaf spotting. Recently, Miller has reported the existence of physiological
races within each species (93) which may complicate breeding programs.
Resistant varieties may result from some of the current breeding pro-
grams, but present-day control measures must center in preventing
spread of infection.

276 THE PEANUT—THE UNPREDICTABLE LEGUME

As shown by studies in Georgia (172), the most logical means of pre-
venting spread of infection, is the application of fungicides which kill
conidia on leaflets before they germinate and penetrate leaf tissue. Tests
in Virginia (94) have indicated that plants so protected lose a lower
percentage of nuts in the soil before digging, lose a lower percentage of
nuts at digging, and have a greater total yield. Similar results, particu-
larly in regard to total yield, have been obtained in Alabama (165).

Results suggesting that fungicidal applications sometimes influence
the number of nuts left on the vine rather than total yield have been ob-
tained in Florida. When the nuts left in the soil were added to the har-
vested yield there was no appreciable difference in total yields between
control and check plots (20). However, this publication cited the unpub-
lished results of other control tests in Florida carried on over a period of
5 years and these other tests indicated a 15 to 20 percent increase in yield
of harvested nuts. Also, the weather of the particular year in which these
experiments were made was conducive to leafspot so that no correlation
was evident between treatment and leaf-spot control.

Various fungicides have been tested as dusts and sprays (94, 165,
172). Pending further testing of newer fungicides it seems that either
sulfur or 10-90 copper-sulfur with the mixture containing the equivalent
of about 3.5 percent metallic copper are to be recommended as dusting
materials. Spraying with Bordeaux (6-2-100) gives satisfactory control
but is no better than dusting.

The following general recommendations for procedure in dusting for
leafspot control have been modified from Woodroof et al. (172) after
checking for agreement with Miller (94) and with Wilson and Arant
(165):

1. Practice rotations of fields to peanuts at 3-year intervals. Maintain
vigor of plants by fertilizer, cultivation, etc.

2. Dust with conditioned dusting sulfur (at least 93 percent through
325 mesh) or copper-sulfur 10-90 (34 percent basic copper sulfate 10
parts, dusting sulfur 90 parts).

3. Begin dusting about 90 days after planting.

4. Apply dust every 10 to 14 days. If rain occurs within 24 hours
after first dust, repeat after 7 days. If rain occurs within 12 hours after
later dusts, repeat dusting as soon as possible. Continue dusting to within
14 days of harvest. Three to five applications usually are required.

5. The size of the vines determines to a considerable extent the
amount of material required for coverage; 12 to 15 pounds per acre of

_ PEANUT DISEASES 277

material will do for first dusting, 15 to 20 pounds per acre for later dust-
ings. A visible coating of dust should cover the stems and both surfaces of
leaflets.

6. Use any tractor or power row-crop duster which will permit di-
recting some dust at ground to insure bounce to cover lower surface of
leaflets. A short canvas hood should extend to lower edge of nozzles in
front and drag the top of the plants behind. This hood permits dusting
any time except when wind velocities are very high, and insures better
coverage of the plants.

SCLEROTIUM BLIGHT OR SOUTHERN ROOT ROT

Sclerotium rolfsit Sacc. causes three distinct diseases of peanuts: (A)
Root and crown rot of plants in intermediate and advanced stages of
growth; (B) soil-rot of pegs (gynophores) and pods of fruits approach-
ing maturity ; (C) blue-black discoloration (‘“‘blue-damage”’) of the seeds
of Spanish-type peanuts.

The present discussion is concerned only with the root and crown rot.
This is the most spectacular disease of the Spanish peanut belt of the
southeastern United States and, consequently, is known by a variety of
names. The more commonly encountered names are “southern root rot,”
“southern blight,” “blight,” “white mold,’ (sometimes ‘blue mold’’)
and, in other regions, “crown rot,” “foot rot” or “Sclerotium wilt.” All of
these names indicate some recognition that the causal organism is a gen-
eral pathogen and not specific to peanuts. The inclusion of “southern” in
the name of the disease indicates that the disease is usually confined to
warmer regions. Of the names given the disease “Sclerotium blight”
seems preferable since the disease is not confined to peanuts, and is not
localized in the “South”.

Importance. In the earlier days of peanut production in the United
States attacks of Sclerotium rolfsi upon the crown region received con-
siderable attention (2, 88, 150), but for a later period of about 15 to 20
years this disease attracted attention only in the Spanish peanut region of
Georgia (91, 92).

Sclerotium rolfsit has been reported as responsible for deaths of plants
approaching 50 percent of the stand in some instances in North Carolina
(113) while another report listed Sclerotium blight as the cause of death
of as many as 10 percent of the plants (13). Reports from Texas indicate
considerable loss from the disease every year (1, 149). Other reports
listed losses from S. rolfsii as slight in Mississippi (108) and Virginia
(150). Some plant pathologists recognize the importance of the disease

278 THE PEANUT—THE UNPREDICTABLE LEGUME

but feel that S. rolfsit may be a secondary invader and, therefore, are not
willing to attribute the losses to this organism.

Sclerotium rolfsii seldom kills the entire plant of runner peanuts since
portions away from the point of attack are usually supported by the ad-
ventitious root system. Therefore, the disease is not as spectacular on
runner peanuts as on bunch peanuts. There are three general views as
to the importance of S. rolfsi on runner peanuts: (A) Runner peanuts
are sometimes regarded as somewhat resistant to S. rolfsit; (B) S. rolfsu
is sometimes called an important peg-rotting organism, but an unimpor-
tant blight-producing organism on runner peanuts; (C) finally S. rolfsu
is frequently regarded as an important blight-producer on runner peanuts.

Thus, there is a divergence of opinion as to the importance of this
disease in the United States. This undoubtedly results largely from a com-
bination of three factors: (A) The newness of peanuts as a commercial
crop in some areas; (B) a tendency to question the parasitism of Sclero-
tium rolfsii (12, 101); (C) the somewhat different end response to at-
tacks of S. rolfsii exhibited by bunch peanuts as compared with runner
peanuts.

Sclerotium blight is well known in other peanut-producing regions.
In South Africa, where it is known as “foot rot,” it has been reported as
jeopardizing the future of peanut growing (22). In the Philippines, pro-
grams have been initiated, attempting to discover varietal resistance
(115). Losses reported for this disease in Peru vary from light to heavy
(40). A disease has been reported from Rumania (200) and Bulgaria
(34) that appears to be Sclerotium blight. It is a matter of conjecture
whether or not the disease is important in such areas as Australia, al-
though its importance in Ceylon has been questioned (17).

Description. The two most distinctive characteristics of Sclerotium
blight are death of above-ground portions of plants and a mat of white
fungus hyphae and tannish-red sclerotia around stems at the soil surface.
The entire plant or only one or two branches may be killed (22, 92, 150).
When only branches are attacked on bunch peanuts the unattacked por-
tion may remain healthy and vigorous, or it may be stunted and yellow-
ish and have few or no nuts at maturity. The unattacked portions of run-
ner peanut plants usually remain vigorous, although nut production may
be poor.

The center of infection is at the soil surface, and death of above-
ground portions of plants is due to severance of the water-conducting
tissue of the roots and stems. The leaves usually wilt slowly, reviving at
night so that wilting is most evident in the middle or later part of the day.
The leaves turn brown gradually, and several days may elapse before the

PEANUT DISEASES 279

branch or plant appears completely dead. Usually the dead leaves remain
on the branch.

Death of above-ground portions of the plant sometimes takes place
very rapidly, particularly in extremely hot weather. When death is ex-
tremely rapid, the necrosis may develop as a blackening rather than as a
browning. In such cases preliminary wilting does not occur or is evident
for a very short time. Under such conditions Sclerotium blight does not
show the characteristics of a wilt (92).

From South Africa (23) it has been reported that plants infected by
Sclerotiun rolfsii may be conspicuously robust and healthy due to incom-
plete disintegration of the vascular bundles with the xylem remaining
functional. Thus water and minerals move upward, but downward move-
ment of foods is inhibited and there is a surplus of food for top growth.

Organism and pathogenicity. The organism associated with Sclero-
tium blight of peanuts is Sclerotium rolfsii Sacc. This sclerotial fungus
has a basidial ‘‘perfect” stage which is either a Corticium sp. or a Pellic-
ularia sp. (160). Other species of Sclerotium have been reported on pea-
nuts (17, 34, 120) but it seems probable that these are merely forms of
Sclerotium rolfsit.

The basidial stage is very rarely found in nature and pathologists have
continued the use of the name of the sclerotial stage. The fungus is usually
easily identified by the abundance of tannish-red sclerotia which vary in
size from .5 to 2 or 3 mm. or larger. Size of sclerotia apparently depends
upon age, physiological condition, or strain of the organism. The sclerotia
are generally spherical in shape, but may be flattened or otherwise mis-
shapen.

Sclerotium rolfsii frequently produces mycelium on the soil surface or
on decaying organic matter before sclerotia are evident. This mycelium
is a dense hyphal mat which fans out from a central point of origin. The
organism may be identified by microscopic examination since the hyphae
have double clamp connections.

The length of the dormant period of the sclerotia of Sclerotium rolfsii
is governed by food supply and temperature (60). Sclerotia can remain
viable for a considerable period of time. In the southeastern United
States viable sclerotia may be found in the soil throughout the year and
serve as a means of spreading the fungus through or between fields.

Greenhouse experiments indicate a relationship between organic-
matter content of soil and parasitism of S. rolfsit on peanuts (54). In
peanut fields, however, the spots of high organic-matter content are not
necessarily the spots of maximum death from Sclerotium blight.

Sclerotium rolfsii is typically a “warm-region” fungus. Its temperature

280 THE PEANUT—THE UNPREDICTABLE LEGUME

relations seem to be the limiting factor in its geographical distribution
(60). In warmer regions it attacks a wide variety of plants, including
common weeds. The organism has been reported killing almost all cul-
tivated plants grown in temperate and subtropical zones, including seed-
lings of forest trees. Members of the grass family are regarded as some-
what less susceptible, and certain plants such as some varieties of cow-
peas (73) are reported as appearing to be resistant.

The general parasitism of S. rolfsii has been thoroughly investigated.
It seems definitely established that it is a potent parasite on a wide variety
of plants and that its omnivorousness is due to a peculiar type of parasit-
ism (60). The fungus is primarily active in the soil and at the soil surface
(54), and a mat of hyphae is formed over the basal portion of any plants
growing in spots of the fungus. The fungus clings to the epidermis of
plants by holdfasts, and the hyphae secrete considerable quantities of
oxalic acid. Cells of the plant are killed by this oxalic acid in advance of
the fungus hyphae (60). The hyphae apparently do not penetrate living
cells, but will grow into cells killed by oxalic acid. Thus, any plant with
an epidermis permeable to oxalic acid will be killed by contact with the
fungus.

The factors affecting the parasitism of Sclerotium rolfsii, are centered
in the physiological activities of the fungus and not in the reactions of the
host. That the physiology of this fungus in the soil is variable is indicated
by its peculiar behavior in peanut fields. Infections are spotted and these
spots do not appear in the same place in the field from year to year. They
do not appear to be related to soil differences, spots of high organic con-
tent, spots of variable drainage, or any other easily discernible factor. In
a given season, there seems to be no tendency for the fungus to spread out
of these spots.

It has been shown that Sclerotium rolfsii can be seedborne in
peanuts (41, 54, 64, 72, 111, 149), but the possibility of infection from
this source is greatly overshadowed by the possibility of infection from
the soil (142).

Control. At present there seems no basis for making positive recom-
mendations for control of Sclerotium blight on peanuts or other crops.
Although there have been occasional reports of apparent resistance in
progeny resulting from peanut breeding and selection programs (54,
116), the nature of the attack of Sclerotium rolfsii suggests that resist-
ant varieties of peanuts are improbable. There is no reason to expect dif-
ferences in permeability of the epidermis to oxalic acid. There has been
a persistent contention that runner peanuts are less suceptible to Sclero-

PEANUT DISEASES 281

tium blight than are bunch types (22, 92), but many observers feel that
this is actually a difference in response to attack resulting from a differ-
ence in habit.

In the United States it is believed that attacks of Sclerotium rolfsii on
peanuts are less severe in heavy (92) or poorly aerated land (54). In
South Africa it is indicated that well-drained friable soils should be used
for peanut culture to reduce losses from Sclerotium blight (64), although
the disease has been reported from this region as equally severe on all soil
types (22). In Georgia, Sclerotium rolfsii seems less severe on heavier
soils, but these soils are not particularly adapted to peanut culture and are
usually avoided by peanut growers. Deep plowing, recommended in
South Africa for control of Sclerotium blight (22), has not been tho-
roughly tested in the United States.

The number of susceptible crops suggests that it is impractical to
eradicate Sclerotium blight by crop rotation (92). It is reported from
North Carolina that there appears to be no relationship between previous
crops and prevalence of the disease on peanuts (13). In Virginia, how-
ever, an apparent correlation has been observed (150). In South Africa
it is suggested that peanut fields may be cleared of the fungus by follow-
ing peanuts with a grass crop for 2 years, then another legume such as
soybeans the third year (22). Also, in South Africa it is thought that
virgin soils should be planted to a nonsusceptible crop for a year or two
before planting to peanuts (22). In Texas it is recommended that infested
peanut fields be replanted to the apparently resistant varieties of cow-
peas (72). In Georgia a preliminary survey indicated that Sclerotium
blight is more severe on peanuts following peanuts, cotton or lupine than
on peanuts following corn or small grain (52).

Some soil treatments have been tested for control of Sclerotium blight
of peanuts. One test reported no results (92). A report from North Caro-
lina in 1938 indicated beneficial results from some inorganic elements
added to fertilizer and from sulfur and lime applications (111). In 1941,
also from North Carolina, some control was reported from heavy appli-
cations of copper and sulfur to the surface of the soil in peanut rows dur-
ing July and August (101).

At present, therefore, only general recommendations for control of
Sclerotium blight can be made. These include:

A. Plant good, carefully treated seeds to insure proper stand estab-
lishment and initial vigor.

B. Plant seeds thickly to insure good stands.

C. Maintain vigor by dusting for leafspot.

282 THE PEANUT—THE UNPREDICTABLE LEGUME

D. Harvest peanuts as soon as practicable from fields in which
Sclerotium blight is bad.

E. Abandon from peanut culture for several years fields in which
Sclerotium blight appears exceptionally severe.

F. Follow a strict rotation policy in which grass crops play a promi-
nent role in all peanut fields.

DISEASES OF MATURATION—SOIL ROTS OF FRUITS
(PEGS AND PODS)’

In the following discussion the gynophore or fruit stalk is called the
“peg” and considered a part of the peanut fruit. The shell and seed por-
tion of the fruit is called the ‘‘nut” or “pod.” The peanut fruit is usually
called a “peanut” or a “nut.” The peanut differs from most legumes in
that the fruit matures underground and in that the gynophore is con-
siderably elongated. This elongated fruit stalk is usually called the “peg,”
although shriveled, under-developed peanut seeds are also called ‘‘pegs”’
in some sections. :

Importance. By harvesting time in the southeastern United States
many nuts are partially or completely rotted and many seeds of Spanish
peanuts have sprouted in the pod. Many nuts pull off the vines and are
left in the soil. These losses result either from rots or from the pegs be-
coming mature, brittle or otherwise weakened before harvest. These path-
ological and physiological factors are undesirable aspects of the matura-
tion process and are “maturation diseases.”

Several surveys have noted these maturation diseases as important in
peanut culture (11, 95, 96, 119, 125, 127) and a few figures or estimates
of importance are available. In Virginia and North Carolina in 1931
(95) up to 10 percent of the marketed nuts were rotted or ‘‘pickouts.”
The same year losses due to soil rots were estimated as: Virginia 5 to 10
percent ; North Carolina 5 percent average ; South Carolina 5 percent aver-
age on most soils; Georgia 10 to 30 percent in most localities and up to
50 -percent in others; Alabama from 1 to 30 percent in various localities
(98). Surveys in 1943 estimated losses from maturation diseases as:
Virginia 30 percent in one section and from 5 to 50 percent in all sections
(150) ; North Carolina a loss of $20 to $50 per acre; Alabama an esti-
mated average of 12 to 15 percent (139).

Description. Following pollination the peduncle (gynophore) of the
pistil elongates rapidly and becomes the peg. This forces the ovulary into
the soil where most development takes place. Usually at maturity all of
the nut and most or all of the peg are in the soil. The peanut fruit ma-
tures, then, under conditions conducive to attacks of microorganisms,

PEANUT DISEASES 283

If fungi infect the peg it may decay the pod in the soil, or it is weak-
ened so that the pod is pulled-off in the soil or otherwise lost in harvest-
ing. Attacks upon the nut result in discoloration or decay of the shells and
eventually in discoloration and partial or complete decay of the seeds.
This fungous invasion of the maturing peanut fruit may be facilitated by
insect or nematode action (113, 161) but it is not dependent upon this.

Preharvest sprouting of seeds is frequent in Spanish peanuts and
certain peanut varieties other than the common runner that do not re-
quire an after-ripening period before germination. Large numbers of
sprouted seeds are found on Spanish peanut vines when the pegs show
evidence of considerable fungous infection. This indicates that fungi may
be responsible for considerable preharvest sprouting of seeds. Probably
infection of the peg stops the movement of water and food materials re-
sulting in premature ripening and abnormally early germination.

Infection of the peg, however, is the only one of the causes of breaking
of pegs at harvest (139). At maturity all vegetative parts of the plant are
brittle. Premature leaf shedding from disease or insect attacks also has-
tens vegetative maturity and the pegs become brittle abnormally early.

Organisms. Peg breaking or seed damage may result from action of
a number of common soil fungi. Fungi isolated from soil-rotted peanuts
(13, 96, 109, 113, 118) and from peanut seed stocks (41, 44) show that
a variety of saprophytic and parasitic fungi is associated with pod rots.
Nematodes have also been reported as a cause of damage to peanut pods
(113).

Somewhat detailed isolations (161) showed about one-half of the
rotted fruits were infected with miscellaneous molds (Penicillia, Asper-
gilli, Rhizopus spp., etc.). The remainder were infected with Sclerotium
rolfsii, S. bataticola, Diplodia sp., Rhizoctonia spp., or Fusaria. S. rolfsti
was reported several years ago (168) as a cause of peanut fruit rots and in
1931 (91, 98) and 1943 (150) it was reported as the predominant organ-
ism apparently associated with soil rots of peanuts. The variety of fungi
isolated from field-rotted nuts (161) suggests that S. rolfsii is usually not
the most important organism, but rather is only one of several important
organisms.

Early defoliation of plants also causes peg breaking. Thus any dis-
ease or insect injury resulting in leaf shedding will increase losses due to
peg rot.

Some cases of peg breaking can only be blamed on over-maturity of
the pegs at harvest. This is a result of miscalculations and cannot be

called'a disease.
Control. Since maturation diseases are affected by several factors,

284 THE PEANUT—THE UNPREDICTABLE LEGUME

control measures consist mainly of management practices that increase
the vigor of.the plant and prevent premature defoliation. Control of leaf-
spot and leaf insects tends to keep the pegs from becoming brittle pre-
maturely and decreases invasion of pegs by saprophytic fungi and the
natural breaking of pegs at harvest. Apparently fertilizer applications
may sometimes result in more peg breaking at harvest (57). There have
been suggestions of varietal differences in peg breaking at harvest (82),
but more evidence is needed before definite conclusions can be drawn.

Pending further study the following strictly tentative recommenda-
tions for control of maturation diseases are suggested :

A. Keep plants as vigorous as possible up to harvest.

B. Follow a dusting program for control of leaf diseases and insects.

C. Avoid planting peanuts on fields where Sclerotium blight has been
severe on peanuts in the past.

. Avoid planting peanuts on fields where nut rots, peg breaking, or
seed sprouting has been severe in the past.

. Make frequent checks on pegs and pods toward the end of the
growing season. If pegs or pods are beginning to rot, harvest the
crop immediately. If no rotting is evident, harvest the crop before
the pegs become brittle from natural maturity.

IH OO

DISEASES OF CURING

Since the peanut pod develops in soil it is subject to attack by a host
of soil fungi. This invasion begins early (161), and fungi are associated
with the fruit after peanuts are cured (44, 48, 114, 162). If this invasion
were confined to the shell, it would be unimportant, but fungi frequently
grow through the shell and around or into the seeds. This results in
damage to the seeds.

When peanut vines and nuts are stacked, piled or windrowed for cur-
ing, the environment becomes ideal for growth of fungi (49). During
curing, then, there is an excellent opportunity for development of damage
to seeds which were undamaged at digging. Concealed damage and blue
damage are two distinct types of seed damage that develop primarily
during the curing process (48, 49, 162).

CONCEALED DAMAGE

Importance. Concealed damage—sometimes called “hidden damage”
—is a type of seed damage not visible until the seed is broken open. Its
nature, therefore, insures it some importance for its “nuisance value.” It

PEANUT DISEASES 285

is found most frequently in certain varieties of peanuts, but the possibility
of its presence in any variety makes necessary elaborate and time-consum-
ing sampling procedures. Since the price that the grower receives for
peanuts is determined by the shelling percentage and by the amount of
damage in the sample, concealed damage often becomes very important.
It was estimated that in 1945 farmers in Alabama alone lost 2% million
dollars from penalties imposed because of damage (162).

The importance of concealed damage in any given locality depends
largely upon the variety of peanuts grown. Concealed damage is some-
times found in Spanish peanuts (114, 162) but it is rarely of any conse-
quence (48, 162), so that in areas where Spanish is the predominant
variety concealed damage is of slight concern. Farmers in other areas
(162), however, find concealed damage very important. A newer variety,
Dixie runner (30), appears to be less susceptible than the common south-
eastern runner (30, 52, 82, 156, 162). Concealed damage has never been
considered important in Virginia-type peanuts.

A preliminary study of varietal susceptibility has been made in
Georgia (52). From this and other observations the following tentative
grouping of peanut varieties according to apparent susceptibility to con-
cealed damage is offered:

Very susceptible Intermediate
Southeastern runner Dixie runner
(Alabama, Georgia, or Florida

runner, etc.)

Susceptible Somewhat resistant
Georgia bunch Virginia runner
North Carolina bunch Virginia bunch

Uncertain Resistant
Jumbos Spanish

Valencias, etc.

Preliminary data indicate that some unreleased hybrids and selections
of the large-seeded type are more resistant to concealed damage than is
Dixie runner (52). Even though apparent resistance to the disease is not
yet fully explained there is hope that resistant large-seeded varieties will
replace the susceptible types.

Description. Concealed damage is seed decay beginning at the inter-
face between cotyledons and developing outward. The first evidence is a
slight discoloration of this interface, and this is usually followed by defi-

286 THE PEANUT—THE UNPREDICTABLE LEGUME

nite yellowing. With this yellowing a mycelial mat is usually found be-
tween the cotyledons but sometimes this mat is found before discoloration
of the cotyledons is evident. As the disease progresses, the mycelial mat
and cotyledons become darker and eventually the entire seed becomes
black or dark purple. The decay may gradually become apparent from
the exterior of the seeds so that the seed coat becomes shriveled, its color
fades, the seed appears oily, and feels soft (48, 162). Even in this stage,
however, the seed appears normal to all but the most experienced ob-
servers. These symptoms are shown in figure 2.

This semi-detectable stage is soon succeeded by a stage in which the
dark decomposition products are visible from the exterior. At this stage

)

Courtesy Alabama Agricultural Experiment Station

Figure 2,—Concealed damage in runner peanuts. Outside and inside views of healthy

seed at left and damaged seed at the right. The damage on the seed at the ex-
treme right is no longer concealed.

the damage is no longer concealed, but is visible (48, 162). After the
seed are completely decayed it is not possible to determine whether the
infection spread from between the cotyledons or developed inward from
the surface. The important factor is the period in concealed damage dur-
ing which seeds with partially decayed cotyledons appear to be perfectly
sound seeds.

Seeds with concealed damage have a strong, rancid taste (162).
This is the primary danger since a few of these seed taint an entire pro-
duct. In processing peanuts these seed are difficult to avoid since bitter-
ness develops before external symptoms. In addition to rancidity there is
an increase in free fatty acids (162),

PEANUT DISEASES 287

Two other types of interior damage can be confused with concealed
damage. In one type the interior of the cotyledons is shrunken, cracked
and discolored reddish-brown. Apparently this is a physiological trouble ;
no fungi have been isolated from these cotyledons and there is no ran-
cidity. It is rare (162) but has been found in several varieties and is
found more frequently in Virginia peanuts than is concealed damage.
The other type, a soft rot apparently beginning in the “germ,” is rarely
noted (162).

Organisms and pathogenicity. Mycelial mats between the cotyledons
of concealed damaged seeds suggest that a fungus is concerned, and the
disease has been reproduced by inoculations with fungi isolated from
seeds with concealed damage (48).

The lists of fungi isolated from concealed damaged seed in Georgia
(48) and Alabama (162) are strikingly similar. Diplodia sp.® made up
almost 90 percent of the isolations in both cases. Miscellaneous sapro-
phytes—Fusaria, Aspergilli, Penicilli, Sclerotium bataticola, etc.—ac-
counted for the bulk of the remainder. Parasitic forms such as Rhizoc-
tonia solani and Sclerotium rolfsit were rare. S. bataticola, however, was
isolated more frequently in Georgia (48) than in Alabama (162).

Inoculation tests have shown that Diplodia sp. can produce concealed
damage (48). Therefore, it is regarded as the predominant organism in-
volved. Concealed damage was also reproduced by inoculation with
Sclerotium bataticola and perhaps one or two other fungi (48). Thus,
while most concealed damage is due to Diplodia sp., other fungi can and
sometimes do cause the damage. It has been suggested, however, that
Diplodia sp. is the pathogen and other fungi are secondary invaders (162).

Concealed damage usually results from infection which takes place be-
fore peanuts are dug (162). The same fungi may be isolated from sound
seeds and from concealed damaged seeds (48). Concealed damage is
found when peanuts are bought on the market but the disease is rare in
freshly dug peanuts and then is found only in the early stage. It is ap-.
parent, therefore, that concealed damage develops primarily during the
curing season.

The causal fungus invades the intercotyledonary space through the
shell and the placenta (48). Thereafter growth of the fungus is condi-
tioned by moisture content of the seed. The damage develops most rapidly

in green peanuts with moisture contents 15 to 35 percent (162). Above

® The taxonomy of the form genus Diplodia is extremely confused. The fungus isolated from
concealed damaged seeds could he put in any of several species including three species originally
described from peanuts. The present report prefers to regard it as “Diplodia sp.” until it has been
studied further,

288 THE PEANUT—THE UNPREDICTABLE LEGUME

and below these moistures, concealed damage develops slowly, with little
development below 10 percent. There seems to be no relationship between
soil type or fertilizer practices and development of concealed damage.
It may be more prevalent, however, when fields are cropped continuously
to peanuts.

Control. Moisture content being closely related to development of
concealed damage, control measures are centered in attempts at rapid
drying of seeds. Since artificial curing with dry air is still in the experi-
mental stage, control of concealed damage at present is dependent upon
some variation of field curing that hastens the removal of moisture.

The safest method of field curing peanuts is stacking rather than
windrowing or piling in ‘‘cocks” (166). Preliminary studies in Florida
(21) have shown no relation between method of stacking and concealed
damage, but similar studies in Georgia (52) have indicated that signifi-
cantly less concealed damage develops when plants are stacked wilted
(not brittle) than that which develops when plants are stacked “green”
or unwilted.

BLUE DAMAGE”

Importance. Spanish peanuts reaching the market are frequently
graded down because of a prominent blue-black discoloration of many
seeds. In some years this discoloration is not troublesome, but in other
years peanut shellers have reported losses up to 25 percent from this
disease. Sometimes entire lots are rejected by peanut brokers because of
this discoloration.

Description. Usually when blue damage is found in a seed lot, a large
proportion of the seeds is conspicuously affected, though sometimes only
very few seeds are damaged. The discoloration may occur in such an
inconspicuous form and on so few seeds that it is easily overlooked.

This discoloration varies through several shades of blue-black. One
spot may be of several shades, or different spots on the same seed may be
of different shades. Sometimes the discoloration is a streak following
either veins of the seed coat or the suture between cotyledons. The spots
vary in size. The smallest are about 2 mm. in size and of a distinct “bull’s
eye” type with centers bleached, slightly darker, or the natural color of
the seed coat. Larger spots are irregular in shape with no evident center.
All possible variations can be found in a single lot of discolored seeds.

Spanish peanut lots containing blue-damaged seeds generally have

10 This section is a condensation of the report by Garren, Higgins and Futral (49), the only
published work on this disease to date.

PEANUT DISEASES 289

more discolored or otherwise damaged shells than do other lots. These
shell characteristics, however, are sometimes found on shells that do not
contain discolored seeds. In some instances the cotyledons beneath dis-
colored seed coats are not discolored, but generally there is slight yellow
or blue-black discoloration. A few cotyledons underneath discolored seed
coats are conspicuously discolored.

The nitrogen and oil content of blue-damaged seeds and seed coats is
not different from that of normal seeds. The discoloration apparently does
not result in important changes in chemical constituent of the seeds. Ac-
cording to preliminary tests there is no detectable rancidity or off-flavor
in blue-damaged seeds nor does the discoloration have any effect on ger-
mination of the seeds or vigor of seedlings.

Organism and Pathogenicity. Numerous unsuccessful attempts to
isolate fungi from the discolored spots have been made. In rare instances
Sclerotium rolfsii was isolated. It seems apparent, therefore, that the dis-
coloration results from chemical reaction of pigments of the seed coat.
Several facts were evident: Sclerotium rolfsti grew from a few of the dis-
colored spots; it grew readily from shells which contained discolored
seeds; it was known to be prevalent in fields in which Spanish peanuts
were grown; and S. rolfsii secretes oxalic acid which diffuses into plant
tissue in advance of hyphae. A test was made, therefore, in which crystals
of oxalic acid were kept against nuts on living plants in damp soil for
72 hours. Typical blue damage resulted. Inoculation of peanuts with S.
rolfsii resulted in the production of a considerable percentage of blue-
black discolored seeds. Application of liquid from an autoclaved culture
of S. rolfsit to green or partially cured nuts resulted in a lighter form of
the discoloration. It seems evident, therefore, that the discoloration is an
indicator reaction involving pigments of the seed coat and oxalic acid
secreted by S. rolfsit growing in or on the peanut shells.

Most fields of Spanish peanuts in the southeastern United States are
infested with S. rolfsii. When weather conditions or curing methods pre-
vent the rapid drying out of the curing plants there may be continued
growth of S. rolfsii from infested plants in the curing lot. Field studies
show an interrelationship between curing methods, weather conditions,
and development of blue damage. Prominent discoloration is not found
in peanuts cured in stacks during hot, dry weather, but pronounced dis-
coloration is found in peanuts cured in stacks during warm, damp
weather. The blue-black discoloration does not develop in quick-cured
peanuts taken from the same field as peanuts in which blue damage de-
velops during slow curing in warm, damp weather. It is apparent, there-

290 THE PEANUT—THE UNPREDICTABLE LEGUME

fore, that the discoloration develops after peanuts are dug. Development
of the discoloration in peanuts still in the soil or in peanuts in storage
seems negligible.

Control. Considerable development of blue damage is reported from
areas where field windrowing is used for curing peanuts. Absorption of
moisture from soil and dew apparently promotes saprophytic growth
of Sclerotium rolfsit.

Since weather conditions cannot be controlled and since rapid curing
by artificial means is not a general practice, the best control measure at
present is stack curing. If the peanuts are allowed to wilt before stacking,
symmetrical stacks can be constructed that will facilitate curing.

STORAGE DISEASES—ROTS AND OTHER DISORDERS

Importance. Disorders developing in stored peanut fruits or seeds are
of importance primarily to peanut brokers and processors. An occasional
rotten or rancid seed may ruin a peanut product (169).

No information is available regarding the importance of storage
diseases of peanuts to the peanut industry but personal conversations
indicate that considerable loss sometimes is incurred.

Description. Of the disorders developing in stored peanuts, some are
pathological and some are purely physiological. The pathological develop-
ments may have physiological end effects which obscure the initial patho-
logical activity. Rancidity, for example, may develop from undetectable
or incipient concealed damage, from visible rot, or from an independent
enzymatic reaction within the embryo.

Table 4 lists the major storage disorders of peanut seeds, with prob-
able initial causes.

Of these storage disorders, rots, rancidity and reduced vitality are
more frequently encountered. Seed-coat discolorations and bleaching not
accompanied by rot do not affect the use of the seeds for most processing
or for seed stocks (49). Brittleness and sogginess in stored seeds may be
accompanied by physiological changes of a detrimental nature, but this
can not now be confirmed.

Blue damage and concealed damage undoubtedly can develop during
storage of peanuts, but neither has yet been found developing to any con-
siderable extent in storage (48, 49). Progress of concealed damage into
seed rot during storage is probable also (48, 162), but has not been veri-
fied. Reduction in vitality of seeds during storage, the physiological
activities involved, and the factors affecting these physiological activities
are also suppositionary at present.

PEANUT DISEASES 291

Organisms and factors involved. As discussed previously, a fungus
flora develops in the peanut fruit in the soil (48, 161) and viable fungi
are associated with peanut fruits and seeds after curing (48, 114, 162) and
storage (44). These are primarily saprophytic fungi (44, 48, 114, 162)
which may, under favorable conditions, produce rot or other seed damage.

The activity of fungi will be conditioned or limited by a number of
factors. The most important of these factors appears to be temperature,
moisture and time. Thus, rots, discolorations and fungus-produced ran-
cidity and flavor changes which occur in storage will be influenced by

Table 4.—MajJor STORAGE DISORDERS OF PEANUT SEEDS

Disorder Initial cause Reference
Concealed damage........ fungi (48, 162)
Seed rots.............00. fungi, bacteria (170) and common
observations

Blue damage........... fungus (49)
Other seed coat

discolorations...........] fungi or enzymatic Common observation
Seed coat bleaching....... fungi or enzymatic Common observation
Brittleness............... low moisture (170)
Sogginess. os isch saevevees high moisture (170)
Rancidity................ fungi, or bacteria or (162)

enzymatic (170)

Reduced vitality .
(germination).......... fungi, enzymatic, etc. Common observation

these same factors. Woodroof et al. (170) studied moisture content in
relation to fungus development in stored peanuts. Their results indicate
that unshelled, untreated, raw peanuts do not become evidently molded
when stored at 6 per cent moisture or below, become slightly molded
when stored at 6.5 to 7.5 percent moisture, and become pronouncedly
molded at 10 percent moisture or above. For shelled peanuts the moisture
content at which fungus development becomes evident and pronounced is
slightly higher.

In this same study (170) the effect of relative humidity of the
storage atmosphere plus time of storage on fungus development were
tested. At 80 percent relative humidity fungus development was evident
at 120 to 180 days and pronounced after 240 days. At 65 percent

292 THE PEANUT—THE UNPREDICTABLE LEGUME

and 50 percent relative humidity no pronounced fungus development
was noted at the end of 360 days. It is indicated, indirectly, that peanuts
stored at 80, 65 and 50 percent relative humidity will have moisture con-
tents of approximately 10, 6.5 to 8, and 4 to 6 percent, respectively (170),
and the effect of relative humidity on fungus growth must be through
the moisture content of the seed.

Some rancidity developing in storage is not associated with fungus
activity but the result of enzymatic action. This also appears to be con-
ditioned by the factors of temperature, moisture and time. In the same
study (170) rancidity was measured by means of organoleptic tests and
peroxidase values. In general, rancidity developed along with or slightly
earlier than evident fungus activity. Apparently no attempt was made to
determine whether any rancidity developed independent of fungus
activity. It was concluded, however, that “at 50 percent relative humidity
storage life depends primarily on the development of oxidative rancidity
or some other factor independent of moisture changes. . . .” Apparently
at 50 percent relative humidity rancidity does not develop as soon as it
does at 65 or 80 percent, but once beginning it develops more rapidly
(170). This may mean that rancidity developing at 50 percent relative
humidity is purely enzymatic in origin.

Brittleness and sogginess are primarily a matter of moisture lost
or absorbed by the cotyledons. Brittleness develops when the moisture
content falls below 4 percent and sogginess develops at moisture content
above 10 percent. It may be assumed that the loss of viability of peanut
seeds in storage will be closely correlated with fungus and enzymatic
activity and thus conditioned by the same factors.

Control. Peanut brokers, in general, avoid storing peanuts with
moisture content above 8 to 10 percent, but the study cited (170) recom-
mends that the moisture content of stored peanuts should be held at
about 5 percent with the storage atmosphere at about 60 percent relative
humidity.

Present recommendations for control of storage diseases of peanuts
may be summed up as follows:

A. Cure and dry the peanuts as thoroughly as possible before storage.
B. Control aeration in the storage area so that the relative humidity
of the storage atmosphere is kept as low as possible.

PEANUT DISEASES 293

PEANUT DISEASES OF MAJOR IMPORTANCE
IN OTHER AREAS

Virus diseases, bacterial wilt, and rust—major diseases in some
peanut-producing regions—have never been considered important in
the United States. Both viroses and bacterial wilt appeared in the East
Indies and spread to other regions. Virus diseases are of major im-
portance in Africa; bacterial wilt is of major importance in the East
Indies. Peanut rust is a disease of the West Indies, but has been re-
ported from Africa and the United States.

VIRUS DISEASES OF PEANUTS

General

History. In 1907 a peanut “krauselkrankheit” (curl disease) was re-
ported from Java (175). According to Storey and Bottomley (143) a
similar or identical disease was noted in South Africa about 1909.

The name “rosette” was applied to the South African curl disease
about 1925 (3, 143). Storey and Bottomley in 1925 (143) regarded
rosette as definitely a virosis and transmitted the disease. Rosette was
reported from equatorial Africa in 1926 (24), and was reported ex-
tensively from the African region thereafter. In 1945, rosette was
noted as one of the three most important diseases of peanuts in Rhodesia,
South Africa (64).

Virus diseases other than rosette have been reported from other
areas. Mosaic was reported on peanuts in Argentina in 1936 (133) and
in China in 1939 (174). In 1941 Costa (38) described a “ring spot” of
peanut in Brazil as a virosis. KenKnight in 1941 (75) reported a trans-
mittable virus disease, called “stunt,” of peanuts in Texas. Jensen in
1948 (71) regarded virus diseases of peanuts as apparently unimportant
in North Carolina but recognized the following: A leaf mottling
(mosaic?) as a transmittable virosis; a ring spot as a fairly definite
virosis; a rosette-like disease and a witches’-broom, both somewhat in-
definite as to nature at present. Similar conclusions were later reached
by Cooper (37), and most of these conditions have been reported from
Australia (99). At present, then, there are only four described diseases
of peanuts more or less definitely connected with viruses: Rosette,
mosaic, ring spot, stunt.

There is considerable confusion as to the various viroses or probable
viroses of peanuts. Several different conditions have been described as

294 THE PEANUT—THE UNPREDICTABLE LEGUME

probably due to the rosette virus (158). Typical mosaic conditions have
been described from Africa (56) and the East Indies (175) as rosette,
and yet mosaic has been reported by observers unwilling to regard it as
a phase of rosette. In spite of this confusion, however, certain tentative
conclusions may be reached, largely as a result of opinions expressed.

ROSETTE

Importance. Several reports include statements which may be used
in evaluating the importance of the virus disease called “rosette.” This
information is condensed in table 5.

Table 5,EsTIMATES OF IMPORTANCE OF ROSETTE

Year of Area Observations on
report reported on importance of rosette Reference
1907 East Indies Serious loss (175)
1945 South Africa One of 3 most important diseases (64)
1926 Gambia 78 percent infection, yield decrease
66 percent (81)
1937 French West Africa | 75 to 80 percent loss (107)
1937 Ivory Coast Vine weight loss 61 percent
Pod weight loss 81 percent (112)

Description. Rosette is characterized by a “condensation” of the
plant. Petioles and internodes are shortened, giving the plant a typical
rosette or clumped appearance. Storey and Bottomley in 1928 (144)
gave a detailed description of peanut rosette as it was then recognized,
and the following description is condensed from their report:

The whole plant is severely stunted. Leaves, especially the
younger ones, are more or less definitely chlorotic and faintly mottled.
New leaves are pale yellow with dark green veins. Successive leaves
are smaller, curled and distorted, uniformly yellow, and without
green veins. These leaves usually turn green and eventually appear
almost normal. Yield depends upon time of infection. If infection is
early, small, sessil flowers which do not open may be formed, but
they do not mature into fruits. If plants are infected after seeds begin
forming low yields may be obtained. The disease is transmitted by
grafting, is not seed-borne, or soil-borne.

An earlier observation indicated a general deterioration of infected

PEANUT DISEASES 295

plants before the disease became visible. This would result in a reduced
number of nuts with many seedless pods (24). Nuts, formed on rosetted
plants, were also noted as having a lower shelling percentage (27).

It appears that at least two distinct types of symptoms, other than
the typical, have been recognized and called rosette, and subtypes or
variations of each in turn have been recognized and described. The fol-
lowing outline is based upon various published descriptions and the
summary of Weiss (158).

VARIATIONS OF ROSETTE

(A) Typical rosette (Storey and Bottomley (144)).
(See description above)

(B) Chlorotic rosette
Variation 1. Mosaic rosette: Mottling of leaves, no marked
yellowing. Less severe stunting or rosetting (Storey and Bot-
tomley (144) and Hansford (56) ).
Variation 2. Yellows: More pronounced chlorosis, very pro-
nounced mosaic. No typical rosetting (Hansford (56)).

(C) Nonchlorotic rosette.
Variation 3. Green rosette: Leaves darker green than normal.
No chlorosis (Hayes (59) and Porteres and Legleu (112)).
Variation 4. Clump rosette: Leaves normal green in color,
rosette condition more pronounced than typical or other
variations (Porteres and Legleu (112)).

Of these variations the mosaic type and the clump type are infrequent
(56, 112), while typical rosette and yellows have been reported as having
the greatest effect upon yield (56).

The Virus and pathogenicity. There are no indications that the virus
(or viruses) associated with rosette has been isolated or otherwise studied.
Weiss (158) recognized two acceptable technical names for the virus—
Arachis Virus 1 or Marmor arachidis.

Peanut rosette has been transmitted by grafting (144) and by the
legume aphid (135, 143). Later reports noted that the disease could not
be transmitted to other legumes (141) nor could a rosette-type disease of
a wild plant in the Congo be transmitted to peanuts (135). Weiss, how-
ever, lists a butterfly pea, Centrosema plumeri Benth. as another host of
the virus (158).

The legume aphid, Aphis leguminosae Theob. is considered to be the
vector of peanut rosette virus (135, 143). Other insects, which have been

296 THE PEANUT—THE UNPREDICTABLE LEGUME

suspected in regions where the legume aphid is rare, appear to have been
eliminated from consideration.

Several factors seem to influence the pathogenicity of the rosette virus.
These factors, obviously, may be effective on the peanut plant or on the
aphid vector. The most important factors are:

(A) Season. In Africa late plantings are more severely attacked by
rosette (24). Plants not infected during the first 8 weeks of the season
apparently remain uninfected (25). Rosette has been reported more
prevalent (27) and spreading more rapidly (24) in dry seasons.

(B) Soil Moisture. Possibly many of the apparent seasonal effects
are actually effects of variations in soil moisture. An early report indi-
cated a greater degree of susceptibility to rosette during a rainy period
following a long drought (175). If there is scant rainfall in the first month
of the growing season, rosette may be intensified (25).

(C) Vegetative covering. Certain observations indicate that denser
vegetative coverings in peanut fields make for less severe rosette. Weed-
ing does not prevent the spread of infection, but weed covering between
peanut rows apparently results in reduced infection (27, 59, 135). Plants
on the border of a field are reported most frequently infected (59).
Whether these effects are independent of the effect of shading on soil
moisture is not clear. Possibly there is some effect of these dense vege-
tative coverings on the vector.

Control. Some reports from Africa (25) have indicated that com-
monly grown varieties are susceptible. In the Gambia region, the Philip-
pine pink, a local section from Tennessee red, is regarded as resistant
(26) with the Philippine white either less resistant than the pink or not
resistant at all (26).

From Gambia (6) and the Congo (7) it is reported that various con-
trol measures have reduced the incidence of rosette so that it is no longer
serious. The following control measures have been recommended in ad-
dition to the use of resistant varieties:

(A) Seed treatment, insuring good stands and vigorous, drought-
resistant plants (64).

(B) Early planting (142).

(D) Close planting for greater covering of soil surface (142).

(E) Roguing of volunteer peanuts (142).

(F) Roguing of infected plants (112).

PEANUT DISEASES 297

(G) Spraying for control of vector (107).
(H) Grass mulching of soil (141).

BACTERIAL WILT—SLIME DISEASE

Importance. Bacterial wilt or “slime disease’, the first recorded
important disease of peanuts, was observed in the East Indies around
1905 with losses of at least 25 percent (23). The disease was investigated
extensively in the East Indies thereafter until 1937 when a gradual de-
crease in the importance of the disease was noted (154). Slime disease of
peanuts was reported, without estimates of importance, from various
regions and in South Africa the disease became of sufficient importance
for an extensive study to be made in 1930 (87).

In the United States bacterial wilt of peanuts has generally been
regarded as of minor importance. The disease was noted in North Caro-
lina in 1912 when about 15 percent of Spanish peanuts on soil known to
be infested were diseased (47). Wartime plant disease surveys (1944)
reported some bacterial wilt of peanuts in the United States (13, 140).
Experimental host range studies made in North Carolina in 1917 sub-
stantiated the general conclusion that the disease is relatively unim-
portant on peanuts in the United States since peanuts were placed in the
“very slightly susceptible” class (131).

Description. As slime disease of peanuts was observed in the East
Indies, attacked’ plants usually wilted rather suddenly with leaves on dead
plants sometimes remaining green (23, 106). Slight, early infections, how-
ever, were usually overcome (106). Apparently the disease developed pri-
marily in patches and general attacks over an entire field were very rare
(23). In contrast to this are the descriptions given from the United
States where the disease appears to be much milder (92, 136).

The attack of the causal organism is centered in the conducting cells
of the roots and stems (23). One diagnostic characteristic is a large
number of dead roots (106). Bacterial colonies form throughout the root,
main stem and lower branches (23). These colonies are evident as streaks
of brown or black discolorations (23, 106). The original point of entrance
is possibly an insect wound or a lenticle (143). The infected tissue is
finally blackened with extensive plugging and necrosis. If young plants
are attacked the pods are invaded and remain small (106) or become
wrinkled and develop a spongy decay (23). Shells of well-developed
fruits have been found to contain the bacteria. (106). When relatively

11 Slime disease” is a general term applied to the effects of Bacterium solanacearum on a
large number of hosts.

298 THE PEANUT—THE UNPREDICTABLE LEGUME

mature plants are attacked there is no evidence of an invasion of the
fruit (23).

When not otherwise evident the infection may be detected in cross
sections of stems and roots. Dark-brown spots are usually evident in the
cut xylem and pith regions (143) though healthy appearing plants may
be filled with bacteria without any discoloration of the vessels (106).

Organism and pathogenicity. Since about 1911 Bacterium solana-
cearum (E.F.S.) E.F.S. has seemed definitely established as the patho-
gen of the bacterial wilt of peanuts. Inoculation tests have established that
a typical slime disease is produced when peanuts are inoculated with B.
solanacearum isolated from peanuts or other plants (87, 136). The nomen-
clature of the pathogen of slime disease is not definitely established, how-
ever, and it has been placed in four genera other than the genus Bac-
terium.

With a number of plants reportedly susceptible the existence of dif-
ferent strains of the bacterium seems likely. Early observations in the
East Indies suggested the existence of a strain equally pathogenic to pea-
nuts, tobacco and tomatoes (23, 122) and another strain more pathogenic
to eggplant, potatoes and local species (122).

In the United States, B. solanacearum has been investigated most
frequently in connection with the “Granville wilt” of tobacco, and bac-
terial wilt of peanuts was first noted on peanuts grown in rotation with
tobacco (47). The bacterium from tobacco was successfully cross inocu-
lated into peanuts. Further studies showed that numerous other species
of cultivated plants and weeds are susceptible to the bacterium (131, 136).
In South Africa cross-inoculation tests indicated that tomatoes and only
one variety of tobacco were partially susceptible to the bacterium attacking
peanuts (87). These results suggest the existence of different strains of
the bacterium in the three widely separated peanut-producing areas, and
this may explain the apparent unimportance of the slime disease of
peanuts in the United States.

Factors most frequently suggested as affecting the pathogenicity of
B. solanacearum on peanuts are soil type, soil moisture, and rotation
practices. The virulence of the organism on peanuts in the East Indies
was found to be higher on more moist soils, on heavy clay soils, and on
soils planted to peanuts for several successive years (106). Continuous
cultivation on irrigated soils resulted in an apparent increase in infections
in dry seasons (121). In South Africa repeated cropping to peanuts in-
creased the severity of the disease which was apparently restricted to the
heavier loamy soils (87). This emphasis on soil texture and drainage sug-

PEANUT DISEASES 299

gests that sandy soil may be an important factor in making bacterial wilt
relatively unimportant in the United States.
Control. Planting of a resistant variety is the most convenient means
of controlling the slime disease of peanuts. From selection work in the
East Indies has come the variety “Schwarz 21” which appears to have
considerable inherited resistance to the disease. In 1937 this variety was
reported as resulting in considerable decrease in loss from bacterial wilt
in that area (106).
A few attempts have been made to control B. solanacearum by soil
treatment. Those treatments which might be applied to peanuts offer
little hope (42, 110). Application of sulfur to East Indies soil gave no
beneficial results on peanuts (42).
The control measures recommended in addition to the use of resistant
varieties of peanuts are:
A. Seed treatment ; the bacterium can be seed-borne (106).
B. Planting on light, well-drained soil (87, 106).
C. Rotation with crops which seem to be resistant to B. solanacearum
such as sweet potatoes, grains and certain legumes (131).

D. Variation of the rotation to prevent building up other disease-pro-
ducing organisms in the soil to the extent that the effects on pea-
nuts will be more detrimental than that of B. solanacearum.

PEANUT RUST

Importance. Peanut rust, first described from Paraguay (28), ap-
parently is distributed throughout South America (10). There are no
direct indications of the past or present importance of peanut rust in
South America, though Arthur (9) suggested that rust is sometimes a
serious peanut disease there.

There is not complete agreement, but it is generally indicated that
peanut rust is serious throughout the West Indies (104). Rust was first
reported on peanuts in this area about 1911 (134) and the peanut crop
was reported “devastated” by rust in the Dominican Republic in 1925

36).

a of peanuts has been reported sporadically from Florida (28,
129). In 1941, KenKnight (74) reported peanut rust from Texas with
seven fields of Spanish peanuts in one county infected.

Description. The existing literature is of little use in evolving a spe-
cific description for peanut rust. The symptoms, presumably, are typical
for rusts with the pustules of the causal organism as the most useful diag-
nostic characteristic.

300 THE PEANUT—THE UNPREDICTABLE LEGUME

The peanut rust organism is found chiefly on the undersurface of
leaves (10), where it appears, first, as necrotic flecks and later as yellow-
ish spots on the upper surface. Spores form in typical sori rupturing the
lower epidermis.

While these necrotic spots do not enlarge much, the infected leaves
soon appear as though burned or scalded (74), and premature defoliation
results (9). It is reported that premature ripening of fruits, and under-
developed, shriveled seeds also result from rust infection (9).

Organism and pathogenicity. There is no agreement as to the proper
name for the causal organism of peanut rust. Arthur, in 1925 (10) re-
ferred it to Puccinia arachidis Speg. as it was originally described.

According to Arthur (9) telia of this organism have been found only
once. It may be presumed that this was in connection with the type speci-
men collection. Pycnia are unknown, and the organism does not have an
aecial stage.

Peanut rust has no alternate host. The uredinial and telial stages
are found on peanuts.

Although not cited specifically, it is presumed that the pathogenicity
of this organism on peanuts has been proven by artificial inoculations.
Arthur (10) lists Arachis hypogaea as the only host. West (159) dis-
cussing the rust in breeding plots in Florida reports it on A. nambyquarae
Hoehne; A. prostraia Benth. and a hybrid of A. hypogaea X A. namby-
quarae. KenKnight’s report from Texas (74) indicates, indirectly, that
selection and natural hybrids within A. hypogaea may sometimes be
highly susceptible.

The organism appears to be seed-borne. It appears to have been
brought into Florida recently on seeds from Brazil (159), although the
rust had been reported from Florida twice previously (8, 129).

Some factors have been indicated as affecting the virulence of the
organism. Arthur (9) concluded that peanut rust is more prevalent in wet
seasons, with very little damage when infection is accomplished late in the
growing season. In the West Indies the degree of infestation appears to
depend largely on climate and condition of the soil (104). When con-
ditions favor growth and vigor of peanuts only leaves approaching senility
are infected. Under less favorable conditions infection is higher and
results in death of the entire plant.

Control. Spraying with Bordeaux mixture has been reported as in-
creasing the yield of rust-infected peanuts in the West Indies (104). Ina
3-year experiment (104) it was finally concluded that while two applica-
tions of Bordeaux produced some beneficial results, it could not be said

-— Ee

PEANUT DISEASES 301

that measurable control was achieved unless more than two sprays were

applied. Arthur (9) regarded attempts to control the rust with Bordeaux
sprays as “not achieving much success.”

DISEASES OF APPARENT IMPORTANCE IN LOCALIZED
AREAS

Three peanut diseases have been reported in recent years from defi-
nitely limited areas. It is indicated, directly or indirectly, that these
diseases are of importance where found. It may be assumed that such
diseases are a potential threat to other peanut producing regions.

1. Sphaceloma scab (Brazil)

A scab disease of peanuts caused by Sphaceloma arachidis Bitt. and
Jenk. has been reported from: Brazil with pathogenicity of the organism
demonstrated (19). Species of Sphaceloma (Elsinoe) are associated with
destructive anthracnoses of many plants.

The main symptom of this type of anthracnose is the small necrotic
or hyperplastic lesions on leaves, hence the name “‘scab” for the disease.
The lesions on peanuts are found predominantly on leaves, sometimes on
petioles and stems (19). On leaves they are found on veins as well as be-
tween veins.

Sphaceloma scab was reported severe on peanuts in Brazil in 1938
with much less severe infection in 1939 and 1940 (39). Some varieties
showed apparent resistance (39). No specific control measures have been
recommended.

2. Aspergillus crown rot (Queensland, Australia)

A seedling blight or crown rot of peanuts has been described from
Australia and an Aspergillus sp. is regarded as the pathogen (99, 100).
The disease develops on plants from germination to maturity but is most
important as it affects the initial stand since pre-emergence losses are
greatest. Infection apparently takes place through lesions in the seed coat
and spreads from cotyledons to the stem.

When plants approaching maturity are attacked, there is a general
wilt. Sometimes a mass of spores of an Aspergillus sp. is found in this in-
fected tissue. No inoculation tests appear to have been made, but it is
assumed that this Aspergillus sp. is pathogenic.

Observations indicate that the disease is worse under conditions of
high soil moisture, low fertility, unfavorable soil texture, and continuous
cropping to peanuts. Recommendations for control are: Avoidance of
excessive seed injury, seed treatment, planting of peanuts in rotation with
corn, small grains, or grasses (99, 100).

302 THE PEANUT—THE UNPREDICTABLE LEGUME

Aspergillus rot is in part a pre-emergence disease and is most serious
in that aspect. The post-emergence aspects of Aspergillus crown rot
strongly resembles collar rot!” of the southeastern United States.

3. Texas Root Rot (Southwestern United States)

In the southwestern United States Phymatotrichum ommnivorum
(Shear) Dugg. causes a root rot of a number of plants. This root rot is
generally regarded as the most important plant disease in that area (31).
Peanuts have been reported attacked by this organism in Texas, Arizona
and New Mexico with greater losses on heavier soils. In one survey ina
Texas county, 7 of 11 peanut fields were found infected with losses of at
least 15 percent in most fields and up to 83 percent in some fields (75).

Fine, brownish strands of the fungus cover the roots of infected
plants before above-ground symptoms are evident. Under moist conditions
spore mats appear on the soil above infected roots. These mats are 2 to 12
inches in diameter, are originally white and cottony but turn tan with
spore formation. The fungus forms rhizomorphs and pinhead size scler-
otia. The sclerotia are light tan, and become darker and warty with age.
The sclerotial stage has been called Ozonium omnivorum Shear. The
foliar response is wilting, with death occurring in a few days. The entire
root system decays and the plant slips from the soil easily.

It is suggested (75) that damage to peanuts by Texas root rot in-
creased as a result of expanding peanut acreage to heavier soils as well
as to soils known to be infected. Chester (31) suggests the following prac-
tices for the control of Texas root rot: (A) Three- or 4-year rotations of
susceptible crops with highly resistant crops, such as grains; (B) avoid-
ance of susceptible perennials, such as alfalfa, and certain trees and orna-
mentals; (C) promotion of soil organisms antagonistic to Phymatotri-
chum omnivorum through the use of manure or other organic fertilizers ;
(D) clean cultivation to eliminate susceptible weeds.

DISEASES OF MINOR IMPORTANCE

Quite a few diseases of peanuts appear to be unimportant wherever
they occur. These diseases fall into two classes: (A) Diseases known to
be of minor importance, and (B) diseases which cannot be definitely
classified because they have not been extensively studied.

All of these diseases may be important under abnormal environmental
conditions, thus such diseases should be regarded as potential threats.

12 See page 269 for discussion of collar rot.

PEANUT DISEASES 303

Puytvosticra LEAFspot

In the southeastern United States primary and other seedling leaves
of peanuts are always infected with a leaf-spot organism. The spots differ
from typical peanut leafspot (Cercospora spp.) in being smaller, more
irregular, without definite halos, and in being found only on juvenile
leaves. Moist chamber culture of leaves shows that a Phyllosticta sp. is as-
sociated. This organism apparently cannot infest older leaves. It is also
apparent that the peanut plant is not noticeably damaged by these leaf-
spots on younger leaves. There is also a report from Burma of the occur-
rence of a Phyllosticta on peanuts (117).

Fusarium WItt or Root Rot

Many peanut-disease surveys made in southern United States have
listed Fusarium wilt on peanuts. In Texas a seedling blight, apparently
due to a Fusarium sp., was regarded as one of several factors necessitat-
ing replanting of several fields in 1941 (75). In Georgia in 1932 (92) it
was reported that an early or seedling wilt caused by F. martii var
Phaseoli Burk. depleted stands from 10 to 38 percent in some counties.
Fusaria can be isolated from peanut seeds readily and isolations from
“diseased peanut tissue” in North Carolina were approximately 50 per-
cent Fusaria (101).

In 1932 a Fusariin sp. was shown, by inoculation, to be the cause of a
“destructive” wilt of peanut in Kenya, Africa (89), but since then con-
tinuous selection has maintained sufficiently high resistance to keep up
production (65).

The following description of a Fusarium wilt of peanuts is based on
that given by Miller and Harvey (92) from Georgia: Maximum infection
occurs at blooming. Entire plant is usually killed, but sometimes only the
shoots. Lesions on roots at first are small, elongate, light-centered with
darker edges. Roots eventually are girdled by enlargement of lesions. Rot
progresses through the roots with hyphae evident in the disintegrating
tissue. There is no plugging of xylem vessels. In advanced stages the
taproot is rotted just below soil surface.

The Fusarini “wilt” of peanuts, as described, is not a typical wilt.
The plugging or disintegration of conducting cells usually found in wilts
has not been reported from peanuts. Rather the peanut disease, as noted,
was a typical root rot.

It is difficult to establish the pathogenicity of a Fusarium sp. The
-senior author has made numerous unsuccessful attempts to prove patho-

304 THE PEANUT—THE UNPREDICTABLE LEGUME

genicity of Fusaria isolated from diseased peanut roots and stems. Others
have verbally reported similar results. Miller and Harvey (92), in
Georgia, in tests on a Fusarium sp. from peanuts obtained results only
with young plants and with abrasions on roots, and a filtrate of cultures
also induced wilting in young peanuts.

The status of Fusarium wilt of peanuts is indefinite and its importance
questionable. Though reported frequently from southern United States it
has never again reached the proportionate importance attributed to it in
Georgia in 1932 (92). The wilt in Kenya has apparently been brought
under control by the use of selections (65). Further investigation, there-
fore, is needed to clarify the association of the Fusaria with peanut dis-
eases. At present only seed treatment and good cultural practices can be
recommended for control.

ScLEROTINIA BLIGHTS

Species of Sclerotinia have been reported as associated with stem,
root and pod rots of peanuts (35, 85, 146). These diseases appear to be
relatively unimportant and primarily of mycological interest.

According to Chu (35) and Suematu (146) two “new species” of
Sclerotinia (S. miyabeana and S. arachidis) were described from peanuts
in Japan by Hanzawa in 1911. Hanzawa’s report was “privately printed”
and mycologists have regarded the publication of these species as invalid.

According to Chu (35) the Sclerotinia blight of peanuts in Japan and
China is primarily a stem rot, but all parts of the plant are sometimes at-
tacked. Pods may be found containing sclerotia of the organism with
seeds thinly coated with mycelium. Infection from spores is apparently
through wounds except on flower petals, but hyphae from germinating
sclerotia may invade uninjured tissue.

Lesions produced by Sclerotinia miyabeana are reported as purplish
brown, eventually “shade-brown” while those produced by S. arachidis
begin brown and blacken rapidly (35). Botrytis type conidia are fre-
quently associated with the fungus called S. arachidis but have never been
found associated with S. miyabeana (35).

Chu (35) reported several other hosts for these Sclerotinias including
grasses, weeds and garden plants.

A “wilt” of peanuts apparently caused by Sclerotinia trifoliorum
Eriks. was reported from Argentina in 1922 (85). S. trifoliorum is an im-
portant stem-rotting organism of clovers, but this apparently is the only
report of it on peanuts. As control measures it was recommended that
affected plants be destroyed and crop rotation and cultivation to prevent

PEANUT DISEASES 305

excessive accumulations of soil moisture be practiced. There is the possi-
bility that one (or both) of the Sclerotinias on peanuts reported from
China and Japan is the same as this Sclerotinia reported from Argentina.

Botrytis LATE BLicHT

Species of Botrytis have been observed associated with some unim-
portant diseases of peanuts. Possibly these Botrytis spp. are conidial
forms of Sclerotinias but no studies have been made of this aspect.

Suematu (146) in Japan reported peanuts severely attacked by a
Botrytis sp. during persistent wet weather, with the fungus forming
conidia on stems and pods. Attacked pods did not mature and were
later covered with dark sclerotia. Successful inoculation tests were re-
ported.

Typical Botrytis late blight of peanuts has been observed by B. B.
Higgins in Georgia!®. Noted on mature or overmature peanuts, the in-
fection develops during cool damp days of early fall. Growing tips were
attacked and covered with a grey spore mass. Sclerotia were formed on
pegs and pods, a few of which were partially to completely decayed.

It would appear that the parasitism of Botrytis sp. on peanuts may
be dependent upon damp cool weather. Control methods include planting
practices to avoid maturation during such weather.

Asuy Stem Bricut anp DipLopia BLIGHT

In the southeastern United States older peanut plants killed by Sclero-
tium rolfsii, insects, etc. are soon overgrown by fungi. Many living plants
approaching maturity are similarly overgrown, particularly those partially
defoliated by leafspot or -insects. Examination usually shows that these
fungal structures are sclerotia of Sclerotium bataticola Taub., pycnidia of
Macrophomina phaseoli (Maubl.) Ashby, and pycnidia of a Diplodia
sp.

Ashy stem blight. The sclerotia of Sclerotium bataticola and pycnidia
of Macrophomina phaseoli on peanuts give the stems an “ashy” appear-
ance. The structures are regarded as stages of the same fungus, and this
has been demonstrated with isolations from plants other than peanuts
(83).

Most references to Sclerotium bataticola on peanuts are primarily
concerned with the seedling disease “charcoal rot’?*. Observations on a
variety of plants indicate that ashy stem blight results from invasion of

13 Unpublished observations.

14 See previous section on charcoal rot, page 267; also section on concealed damage, pp. 284-288
for another aspect of S. bataticola on peanuts.

306 THE PEANUT—THE UNPREDICTABLE LEGUME

Courtesy Georgia Agricultural Experiment Station

Figure 3.—Botrytis late blight on peanuts.

weakened plants. The organism, while sometimes a vigorous parasite on
seedlings, particularly at high temperatures, appears to be primarily a
weak parasite on older or mature plants. This parasitism of S. bataticola
has been investigated and the various observations summarized (63).
In regard to peanuts, the ashy stem blight needs investigation. It is
possible that following periods of excessively high temperatures, excessive
defoliation, or excessive insect injury it becomes an important disease re-
sulting in death or early maturity of many plants. This insect injury and
defoliations may be prevented to some extent by dusting programs.
Diplodia blight. Diplodia sp. has been reported frequently on peanuts
in the United States (13). It has been shown that Diplodia sp. is fre-
quently associated with peanut seed?’ and thus may be seed-transmitted
(149). A Diplodia sp. is frequently isolated from young peanut plants
with collar rot?® but pycnidia are generally not found on younger plants.
Pycnidia are frequently found on stems of dead or living mature plants ;
thus Diplodia blight is distinctly a disease of older plants. Diplodia blight
is easily confused with ashy stem blight. Frequently pycnidia of both

15 See section on “‘concealed damage,” pp. 284-288,
16 See section on “collar rot,’’ page 269

PEANUT DISEASES 307

Diplodia sp. and Macrophomina phaseoli are found on the same peanut
plant.

Little is known about the parasitism of Diplodia sp. on peanuts. Lack-
ing other conclusive evidence it may be assumed that Diplodia blight
usually develops on nearly mature plants and results in little decrease in
yield and few deaths. The inoculum is probably soilborne. There may be
some carryover from seed-borne inoculum or seedling infection, but such
early infected plants probably die before they reach the stage of maturity
at which Diplodia blight develops.

NEMATODES ON PEANUTS

Three types of nematodes have been reported on peanuts, but only
the root-knot type has attracted much attention.

Root-knot nematodes. Root knot was reported from peanuts in the
United States in 1931 (4) and 1943 (13), but only since 1946 has it been
given more than passing attention. Parasitic nematodes were noted on
peanuts in South Africa in 1926 (137) but apparently were considered
unimportant.

Christie (33) inoculated Virginia runners with nematode populations
from alfalfa, cotton, peanuts and sweet potatoes. After 6 weeks there was
no development of nematodes on peanuts inoculated with sweet potato
populations, but those inoculated with alfalfa and cotton populations
showed nematodes in the larval stages. The peanut plants inoculated with
the population from peanuts showed numerous egg-laying females. From
this Christie concluded that the peanut as a host has a varying effect on
the development of different nematode races.

Wilson (164) noted populations or strains of root-knot nematodes
attacking peanuts readily in North Carolina, Virginia and Alabama, and
evidently on the increase in Alabama. A similar observation regarding
southern Georgia has been received from J. H. Miller?’. Recently Chit-
wood (32) placed the root-knot nematodes in the species Jfeloidogyne
arenaria.

Root knot on peanuts is very similar to root knot on other plants.
Typical galls are produced on the taproot, lateral roots, pegs and shells.
The symptoms are shown in figure 4. If infection occurs early the plants
are stunted and the margins of the leaves become necrotic.

Root knot does not seem to have been a serious disease of peanuts in
the past. It looks as though the strain or strains of nematodes attacking
peanuts are now on the increase in three major peanut-producing regions

17 Personal communication.

THE PEANUT—THE UNPREDICTABLE LEGUME

308

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PEANUT DISEASES 309

of the United States. This disease, then, is a potentially serious disease in
these regions. Rotation offers the only hope for large-scale control. There
is need for research to determine host ranges of the strains attacking pea-
nuts in order that rotation programs can be intiated.

Nematodes and witches’-brooms on peanuts. In 1935 peanuts were
found in Tennessee with typical witches’-brooms and the nematode
Cephalobus elongatus de Man. was isolated from them (5). In 1936 a
similar witches’-broom of peanuts was found in Texas. Isolations yielded
C. elongatus and Acrobeles crossatus Steiner. In the latter case it was
doubted that either nematode was the cause of the witches’-broom.

Meadow nematodes and peanuts. Nematodes of the genus Praty-
lenchus Filipjev cause a general root destruction of many plants (138).
Little is known of the effects of these meadow nematodes on peanut roots,
but they do frequently attack pods, producing black spots and providing
points of entrance for secondary invaders. Steiner (138) has indicated
need for more work on these nematodes. This need is doubly evident for
peanuts because of the possibility of both root and fruit damage.

Rhizoctonia on Older Peanuts

There are references from almost all peanut-producing regions to
Rhizoctonia solani Kuhn on peanuts!®. While usually not stated, it ap-
pears that the primary concern is with seedling diseases.

In the southeastern United States many peanut plants beyond the
seedling stage show typical dry, greyish or reddish-brown Rhizoctonia
cankers on stems near the soil. Although some cankered stems break off
in wind or during cultivation or dusting, few, if any, plants appear to be
killed as a result of this cankering. At maturity numerous greyish-blue
fruiting bodies on the “perfect” stage—Corticium solani (Prill. and De.)
Bound and Galz.—may be found on peanut stems in contact with the
soil. It may be that high temperatures during the growing season are the
important factor in making FR. solani of little apparent consequence on
peanuts beyond the seedling stage.

Possibly attacks of R. solani on the peg are an important factor in
harvest nut losses?®. At present any theory as to R. solani and diseases
of peanuts beyond the seedling stage is purely suppositionary.

18 See page 267 for section on seedling dry rot.
19 See page 282 for section on soil rots of nuts and pegs.

310 THE PEANUT—THE UNPREDICTABLE LEGUME

DEPREDATIONS OF ANIMALS

Animals may damage peanut plants in any stage from the planted
seed to the mature plant. These depredations may be evident in forms
other than the eating of leaves, seeds or nuts. The damage to the peanut
crop caused by animals eating the mature or almost mature pods is some-
times quite spectacular.

Gophers (tortoises) have been noted from Florida (119) as pests of
peanuts, and the western gopher (a rodent) was similarly noted from
Oklahoma (77). Everyone has observed considerable numbers of dead
plants following attacks of moles on the root system. Skunks and wild
turkeys display a fondness for peanut pods in the “milk” stage. There is
nothing, however, which will indicate that any general importance can be
attached to such depredation of animals.

PHYSIOLOGICAL OR NONPATHOGENIC DISEASES OF
PEANUTS

Mineral Deficiency Syinptoms. The chart on next page summarizes
the known mineral-deficiency symptoms on peanuts.

Described Physiogenic Disorders. The following have been specifically
reported as nonpathogenic diseases of peanuts:

“Cluinp” or “Bunch”. “A condition called “clump” or “bunch” has
been described from India. Plants were densely clumped, with tufted and
dwarf shoots, yellowed leaves, arrested growth and erect habit. Yield of
affected plants was reported (147) as only 30 percent of normal. Poor
soil and the use of immature seeds were thought to be responsible. No
evidence of parasitism was noted. It has been suggested that “clump” may
be a phase of rosette but the matter is still indefinite.

Nonparasitic Leafspots. A peanut leafspot characterized by some-
what rectangular, brown to black splotches on the lower surface, with
pin-point necrotic areas was described from Georgia in 1941 (69). The
disorder, found on puddled clay soil, was believed to be a mineral de-
ficiency resulting from the puddling.

Inherited Albinism. Albinism, varying from a few chlorotic streaks in
leaves to complete albinism of the entire plant, is a fairly common occur-
rence in peanut fields in southern United States. This albinism has not
been studied. The only logical explanation seems to be that it is a genetical
condition resulting from chance cross pollination.

Pale Dwarf. A condition called “pale dwarf” reported from Java in
1927 (58) was characterized by early paling and dwarfing of leaves. The

PEANUT DISEASES 311

MINERAL- DEFICIENCY SYMPTOMS OBSERVED ON PEANUTS

Foliar Symptoms

Deficient | Peanut | Age of Reference
Mineral | Variety | Plants Leaves Stems
Nitrogen | Virginia 6 General chlorosis Reddish color (29)
Bunch weeks
Phosphate] Virginia 6 Fully developed Reddish color (29)
Bunch weeks | leaves are dark green
changing to yellow
Potassium] Virginia 6 Light green changing | Reddish color (29)
Bunch weeks | to scorch areas on
margin
Calcium | Virginia 6 Brownish necrotic Disturbances in (29)
Bunch weeks | areas on fully devel- | meristematic re-
oped leaves over gion in late
entire surface stages of defi-
ficiency
Magne- Virginia 6 First in older leaves | Lack of the red (29)
sium Bunch weeks | a chlorosis of leaf coloration

margins, with entire
leaves becoming
chlorotic

Tron Spanish 6 Youngest leaves (132)
weeks | become chlorotic |

Boron Virginia 6 Brownish necrotic (29)
Bunch weeks | areas limited to the
edges of the leaves

Zinc Spanish all No observed symp- | No observed (14)
stages toms symptoms
Manga- Spanish all No observed symp- | No observed (132)
nese stages | toms symptoms
Copper Spanish all No observed symp- | No observed (132)
stages | toms symptoms
Sulfur (No reports in the literature)

Prepared by H. S. Ward, Jr., associate botanist, Alabama Polytechnic Institute, and through his
courtesy. 7

peanuts usually recovered. The condition was believed to be nonparasitic
and caused by excessive heat of surface soil after planting.

Physiological Chlorosis. Chlorosis, apparently neither inherited albi-
nism or associated with viroses, has been reported from Somaliland (18)
and attributed to unfavorable weather and soil conditions. A similar
chlorosis has been reported from Texas as “physiological chlorosis” (75).

312 THE PEANUT—THE UNPREDICTABLE LEGUME

Disease-Like Results of Insects. Certain effects of insects on plants
are sometimes difficult to distinguish from pathogenic diseases. An ex-
ample is “peanut pouts” originally regarded as a disease of unknown
cause. The swollen, distorted areas on leaves and young stems were
shown by Metcalf (90) to be the result of toxins from mass-attacking
leafhoppers. It was later pointed out that thrips injury is also sometimes
referred to as peanut pouts (128).

RARE OR ACCIDENTAL DISEASES

Any crop is sometimes found attacked by fungi under “unusual”’ cir-
cumstances. It is rare that such unusual diseases assume any importance,
and they have never been regarded as important on peanuts. Only a few
diseases of this type have attracted sufficient attention to be reported.

1. Seedling rots caused by mold-type fungi. Seedlings of peanuts are
sometimes killed by overgrowth of mold fungi (72). Almost always
extenuating circumstances are obvious: The seedling has been suppressed
or wounded by growing under a hard soil crust; there has been exces-
sively heavy rainfall coupled with excessively low temperatures ; or some
other equally apparent circumstance. The fungus overgrowth is usually a
Rhizopus sp., Penicillium sp., or Aspergillus sp.

2. Fungus leafspots following insect injury. Typical fungus-type leaf
spotting sometimes develops following insect injury. For example, an
Alternaria sp. leafspot has been reported from Virginia (11) associated
with leaf-hopper damage. Undoubtedly these unusual leafspots are very
unimportant in the total picture of peanut diseases.

3. Diaporthe blight. A situation has been reported from Virginia (12)
in which Diaporthe phaseolorum var. sojae (Lehm.) Wehm. was sus-
pected as the initial cause of the death of peanuts. In a later study (84)
neither the species D. phaseolorum (C. and E.) Sacc. nor the variety
could be shown by inoculation to be pathogenic to peanuts.

4, Anthracnose of peanuts. There are only two reports on the occur-
rence of anthracnose fungi on peanuts. A Colletotrichum sp. was ob-
served on peanut leaves in Uganda, Africa, in 1926 (130) and Colleto-
trichum sp. was the most abundant fungus in a few dark-colored stem
lesions on peanuts in Oklahoma in 1944 (78).

MISCELLANEOUS FUNGI

A large number of fungi have been reported from peanuts only once
and the reports are now buried in obscurity. Host indexes list species of
fungi on peanuts for which it is impossible or almost impossible to find the

PEANUT DISEASES. 313

original reference. Abstracting journals also note many fungi as “on pea-
nuts.” These fungi, which do not seem to be associated with important
peanut disorders, are best classified as “miscellaneous.” To make a de-
tailed listing of such fungi would probably confuse rather than clarify. The
reports on miscellaneous fungi of peanuts fall into three main classes:

(A) Saprophytic fungi included in results of general mycological
surveys.

(B) Fungi suspected of being parasitic on peanuts but which have
not yet merited or received further investigation. Examples of this would
be the Phoma sp. noted on rotting peanut stems in Alabama in 1914 (168)
and the Verticillium sp. found in wilting peanuts in Australia in 1945
(99).

arachidis Woron. listed on “dying peanut leaves” in the Caucasus in
1924 (173).

SELECTED REFERENCES

When appearing in the following references, T. T. means that the title of the
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‘

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1937. SCLEROTIAL WILT OF PEANUTS WITH SPECIAL REFERENCE TO VARIETAL
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1924, REPORT OF THE MYCOLOGIST, BURMA, PERIOD ENDING 30 JUNE, 1924.
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1944. SUMMARY OF OBSERVATION ON PLANT DISEASES IN FLORIDA DURING
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1936. ROOT ROT ON PEANUTS IN NORTH CAROLINA IN 1936. U. S. Dept.
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PEANUT DISEASES 321

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1943, PEANUT SEED TREATMENT. N. C. Agr. Ext. War Series Bul. 18.
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1941. THRIP INJURY ON PEANUT SEEDLINGS. U. S. Dept. Agr. Plant Dis.
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(131) Smit, T. E.
1939, HOST RANGE STUDIES WITH BACTERIUM SOLANACEARUM. Jour. Agr.
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(132) Sommer, ANNA L.
1949, Personal communication.
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1932. (T.T.) A NOTE ON SOME PLANT DISEASES CAUSED BY ‘‘VIRUSES’’ IN THE
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(134) SoutH, F. W.
1911. FUNGUS DISEASES OF GROUNDNUTS IN THE WEST INDIES. West Indian
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(135) Soyer, D.
1939. (1.T.) GROUNDNUT ROSETTE. RESEARCHES ON THE POSSIBLE VECTORS OF
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1917. sTUDIES ON Bacterium solanacearum. Phytopath. 7:155-165.
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1926. PARASITIC NEMAS ON PEANUTS IN SOUTH AFRICA. Centbl. Bakt. 2 Abt.,
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1945. MEADOW NEMATODES AS THE CAUSE OF ROOT DESTRUCTION. Phytopath.
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1944. ROTS OF RUNNER PEANUTS IN SOUTHEASTERN ALABAMA. U. S. Dept.
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1944, PEANUT DISEASES OBSERVED IN ALABAMA IN 1943. U. S. Dept. Agr.
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1936. WITCHES’-BROOM OF PEANUTS. Texas Agr. Expt. Sta. Ann. Rpt. 49:
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1941. PEANUT DISEASES. Texas Agr. Expt. Sta. Ann. Rpt. 54:70-71.
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1941, DETAILED ADMINISTRATION REPORT OF THE GOVERNMENT MYCOLOGIST
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1945. TREAT PEANUT SEEDS FOR BETTER STANDS. Fla. Agr. Expt. Sta. Press
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1937. (1.T.) DISEASES AND PESTS OF CULTIVATED CROPS IN THE DUTCH EAST
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1946. PEANUTS. Fla. Expt. Sta. Ann. Rpt. for 1945-1946, 142.

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1943. PEANUT DISEASES IN TEXAS. U. S. Dept. Agr. Plant Dis. Rpt. 27:
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1945. VIRUSES DESCRIBED PRIMARILY ON LEGUMINOUS VEGETABLE AND
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1949. CONTROL OF INSECTS AND DISEASES OF PEANUTS. Ala. Agr. Expt. Sta.
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1945.

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1945. TREAT SEED PEANUTS FOR PROFIT. Va. Agr. Expt. Sta. Bul. 382.
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(172)

324 THE PEANUT—THE UNPREDICTABLE LEGUME

(174) Yu, T. F.

1939. A LIST OF PLANT VIROSES OBSERVED IN CHINA. Phytopath. 29:459-461.
(175) Zimmerman, A. ;

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INDEX

Ackerman, A. J., 226, 250

Acosta, Jose de, 21, 25

acreage, 4-5, 9-13

Ainslie, G. C., 256

‘Alam, Zafar, 119

albinism, 310

Albrecht, H. R., 115, 132, 167, 172, 195,
209

Alden, C. H., 215, 251

Alexandri, V., 320

Allen, N., 259

Allison, R. V., 106, 116

almond moth, 245, 246

Alstatt, George E., 313

Anderson, Donald B., 119

Anderson, L. D., 251

Anderson, W. H., 237, 242, 250

animal depredations, 310

anthracnose, 312 :

Anticarsia gemmatilis, 198, 210- 216

App, B. A., 261

Arachis hypogaea, early mention of, 18-
19; systematic position of, 50- 60;
varieties of, 60-70

Arachis Virus 1, 295

Arant, Frank Selman, 210-250, 251, 260,
276, 323

armyworm, see fall armyworm ;

Arnon, D. I., 118, 167 ‘

Arthur, J. c. 299, 300, 301, 313-314

ashy stem blight, 267, 305-307

Aspergillus, 264, 270, 283, 287, 301-302,

312
Atkinson, R. E., 314
Aull, G. H., 124, 168
Azemard, 251

Back, E. A., 251

bacterial wilt, see wilt

Bacterium solanacearum, 80, 297-299

Badami, V. K., 23, 25, 34, 51, 52, 73, 74,
77, 78, 80, 83

Bailey, W. K., 116

‘balance, nutritional, 113-114

Ball, E. D., 226, 251
Banerji, I., 54, 83

Barber, G. W., 222, 251, 257
Barnette, R. M., 116, 314

Basheer, M., 252

Batten, E. T., 82, 83, 106, 120, 123, 130,
131, 138, 149, 157, 167, 171, 174,
209, 226, 228, 229, 251, 257, 323

Baxter, Aaron, 120, 121, 171

Beattie, J. H., 71, 76, 82, 83, 85, 100, 116,
157, 167, 189, 209

Beattie, W. R., 68, 83, 157, 167, 314

beetles, flour, 245, 246-247; saw-toothed
grain, 245, 246; white-fringed, 235-
240. See also insect pests

Bentham, G., 19, 28, 58, 59, 60, 83

Bertus, L. S., 314

Beyer, A. H., 227, 228, 251

Bigi, F., 314

Bissell, T. L., 215, 246, 249, 251

Bitancourt, A. A., 314

Blaser, R. E., 116

Blatchley, W. S., 251

Bledsoe, Roger W., 89-115, 116, 118, 167-
168, 314

blights, 157, 198, 277-282, 304-307, 312.
See also diseases

blue damage, 288-290

Bolhuis, G. G., 80, 83

Bond, R. C., 314°

borax, see boron

borer, lesser cornstalk, 243-244. See also
insect pests.

boron, 106, 108, 311. See also nutrition

Boswell, V. R., 83

Botrytis blights, 215, 305-306

Bottomley, A. M., 293, 294, 295, 314, 322

Bouffil, F., 29, 30, 38, 39, 40, 41, 56, 57,
61, 72, 81, 83, 84

Bower, C. A., 171

Bradfield, R., 171

‘Brady, N. C., 55, 84, 102, 116, 117, 119,

120, 137, 143, 145, 146, 153, 168,
170, 171

Breda de Hahn, J. van, 314

breeding, see genetics and breeding

Brewer, H. E., 101, 116

Bridgers, T. F., viii

Bridwell; J. C., 251

Broadbent, F. E., 121

Brooks, A. J., 314-315

Brown, O. A., 190, 209

S20

326

Brownrigg, George, 6, 17

Brues, C. T., 222, 258

Bruner, W. E., 95, 97, 117

Bryan, O. C., 116, 168

Buchanan, L. L., 237, 238, 252

“bunch” (disease), 310

Bunkley, A., 7

Burger, O. F., 315

Burkart, Arturo, 84

Burke, Emily P., 7, 16

Burkhart, Leland, 55, 60, 84, 102, 103,
104, 109, 111, 113, 117, 119, 168, 315

Butler, C. P., 169

cadelle, 245, 247

Cahill, C. J., viii

calcium, 104, 107, 108, 133-155, 311. See
also mineral nutrition

Calderon, S., 252

Calhoun, P. W., 118

Camp, J. P., 116, 153, 172, 314

Candalle, Alphonse de, 19, 26

Candura, G. S., 252

carbohydrate metabolism, see metabo-
lism

Carver, W. A., 81, 83, 315

Casas, Bartolome de las, 20, 26

Cauthen, E. F., 168

Cecil, S. R., 121, 260, 323

Cercospora, 198, 226, 271-277, 303. See
also leafspot

Chaffin, J., 252

Chaffin, W., 168

Champion, G. C., 252

characteristics of plant, 90-97

charcoal rot, 267, 305. See also Sclero-
tium

Cheliadinora, A. I., 98, 117

chemical composition, 106-112

Cherian, M. C., 252

Chester, K. Starr, 317

Chester, K. W., 302, 315

Chevalier, August, 16, 18, 19, 22, 25, 26,
61, 84, 117, 252

Chittenden, F. H., 211, 213, 217, 252

Chitwood, B. G., 307, 315

chlorosis, physiological, 98, 104, 311-312

Chorin, M., 320

Christie, J. R., 307, 315

Christoff, A., 315

Christova, E., 315

Chu, V. M., 304, 315

Ciferri, R., 314, 315

Clark, Fred, 116, 119, 168, 169, 209, 314

INDEX

Clos, E. C., 22, 26, 61, 84

“clump” (disease), 310

Cockerham, K. L., 252

Cole, J. R., 323

collar rot, 269-271, 305, 306

Collins, E. R., 55, 84, 102, 103, 104, 111,
117, 150, 168, 171, 315

Colton, H. E., 8, 9, 16

Colville, Thomas L., 8

Colwell, W. E., 55, 84, 116, 117, 119,
122-166, 168, 170

Comar, C. L., 116, 167

Compton, R. H., 36, 84

concealed damage, 284-288, 305, 306

Cooper, W. E., 293, 315

copper, 105, 106, 108, 149, 150, 311. See
also mineral nutrition

Corbett, G. H., 252

corn earworm, 221-225

Cory, E. N., 222, 223, 253

Costa, A. S., 315

Cotterell, G. S., 252

Cotton, R. T., 251, 252, 253

cotyledons, morphology of, 29, 38-42

Crandall, B. S., 315

Creighton, J. T., 253

Crosier, W. F., 315

crown rot, 301

cucumber beetles, 242. See also southern
corn rootworm

cultivation, 196-199. See also cultural
practices

cultural practices, 173-209

culture of peanuts, see cultural practices

Cumings, G. A., 167

Cummings, R. W., vii, 171

curing, diseases of, 284, 288. See also
harvesting

curl disease, see rosette

Currin, R. E., 116, 209

damping-off, 266-267
Darlington, C. D., 72, 84
Darwin, Charles, 52, 84
Datta, Narayan P., 121
Dean, G. A., 252, 253

Deen, O. T., 252

de Jong, A. W. K., 316

De Jonghe, d’Ardoye E., 253
De Long, Dwight M., 226, 253
Dent, John H., 16

De Ong, E. R., 253
dermestids, 245, 247-248

INDEX

development of peanut industry in the
United States, 6-15

Dew, J. A., 217

Diabrotica, 240-242, 244

Diaporthe blight, 312

Didrichsen, F., 51, 58, 84

digging, see harvesting

Diplodia, 270, 283, 287, 305-307

diseases, 262-313; nutrition and, 114,
128; resistance to, 80, 157

disinfectants, see diseases and insect
pests

Ditman, L. P., 222, 223, 253

Dobbins, T. N., 245, 254

dolomite, see calcium

Donald, Leroy, viii

dormancy of seed, 100-101

» Douglas, W. A., 213, 215, 253

Downing, J. C., 124, 168

Drosdoff, M., 117

dry rot, seedling, 267-269, 309

Dubard, Marcel, 60, 84

Dudley, H. C., 253

Duggar, J. F., 137, 168

Dunlap, A. A., 316, 318

Dunn, Katharine R., 117

Du Pree, M., 246, 249, 251

dusting, 198-199, 215-216. See also dis-
eases and insect pests

Du Tertre, R. P. J. B., 16, 25, 26

Dyar, H. G., 217

Easby, W. B., 7, 16
Economic importance, 3-17
Eddy, C. O., 215, 253
Ejercito, J. M., 169
Elasmopalpus, 243-244
Ellisor, L. O., 215, 253
embryo, morphology of, 54-55
Empoasca, 225-230

English, L. L., 215, 253
Ephestia, 245, 246, 248
epicotyl, morphology of, 29, 40-43
Evans, M. M., 316

Fabricius, J. C., 253

fall armyworm, 210, 216-221

Farrior, J. W., 154, 170

Fenne, S. B., 316

Fenton, F. A., 254

Fernald, H. T., 254

Ferris, E. B., 131, 169

fertilization, 70, 109, 122-166, 174, 194-
195. See also mineral nutrition

327

Filcalho, de, 21, 26

Fink, D. E., 240, 254

Fisher, W. H., 16

Fletcher, T. B., 247, 254

Flint, W. P., 256

flowers, morphology of, 49-51, 55-59, 62;
physiology of, 91-93

Floyd, E. H., 215, 253

foliage, 90-91, 111-113. See also diseases
and leaves

food value, 14, 108-109

Frankenfeld, J. C., 252, 253

Frankliniella, 230-235

Fraps, G. S., 109, 110, 112, 117

Fratzke, W. E., 167

Freid, M., 169

Fronk, W. D., 245, 254

fruit, morphology of, 55-59; physiology
of, 91-94; shedding of, 113. See also
diseases

Fulton, B. B., 254

Fulton, H. R., 316

Funchess, M. J., 137, 168, 178, 209

fungi, see diseases

fungicides, see diseases and insect pests

Fusarium, 81, 264, 267, 270, 271, 287,
303-304

Futral, J. G., 116, 149, 288, 316

Galang, F. G., 84

Gall, O. E., 116, 314

Gallup, Willis D., 110, 117

Garren, Kenneth H., 262-313, 316

Gasso, J. G. C., 16 ‘

genetics and breeding, 70-83. See also
morphology

germination of seed, 100-101

Gilbert, S. G., 117

Gill, J. B., 261

Giri, K. V., 120

Girth, H. B., 254

Glaser, R. W., 239, 254

Geddard, Vera’R., 117

Golding, F. D., 254

Goodman, K. V., 124, 168, 169

Gore, U. R., 154, 157, 169

Graham, L. T., 253

Gray, Asa, 58, 84

Grayson, J. M., 229, 243, 254, 257

Green, G. D., 261

Gregory, C. V., 26

Gregory, Walton C., 28-83, 84, 209

Greulach, V. A., 316

Grizzard, A. L., 121

328

growth-promoting substances, use of,
99-100

grubs, white, 243. See also insect pests

Guerrero, Joaquin, 75, 84

Guthrie, John D., 108, 118, 120, 121

Guyton, F. E., 212, 215, 254

Gwaltney, P. D., 7

gynophore, see peg

gypsum, see calcium

Hammer, C. L., 118

Handy, R. B., 316

Hansford, C. G., 295, 316

Hanzawa, 304

Harper, J. N., 131, 169

Harris, Henry C., 89-115, 116, 118, 149,
167, 168, 169, 314, 316

Harris, T. W., 226, 254

Harris, W. V., 254

Harrison, A. L., 318

Hartley, Carl, 316, 320

Hartzell, A., 254

harvesting, 113, 127, 160-163, 165, 187,
199-208

Harvey, H. W., 303, 304, 318

Harvey, P. H., 45, 75, 84, 87, 94, 119

Harvey, R. B., 119

hay, peanut, see foliage; harvesting

Hayes, R. T., 61, 77, 85, 295, 316

Hayslip, N. C., 260

Hazen, Myron S., viii

Heliothis armigera, 221-225

Henderson, C. F., 254

Hendrix, W. E., 169

Herbert, T. T., 321

Heteroderes, 241, 242-243

Higgins, B. B., 3-27, 79, 80, 85, 118, 275,
288, 305, 316, 317

Hill, A. G., 169

Hinds, W. E., 215, 217, 254-255

Hinton, H. E., 255

Hoaglund, D. R., 118

Hoehne, F. C., 43, 46, 60, 85

Hoffer, G. N., viii

Hoffmaster, D. E., 317

Hoffpauir, C. L., 108, 118

hogs, grazing by, 7, 122-123, 160-163,
165, 208

Holdaway, F. G., 255

Holland, Frank L., viii

Holley, K. T., 118

Hooker, W. A., 234, 255

Hopkins, J. C. F., 317

hormones, use of, 99-100

INDEX

Hosny, M., 255 z

Howard, L. O., 248, 255

Hoyt, L. F., 255

Hull, Fred H., 61, 62, 74, 77, 78, 79, 81,
83, 85, 87, 100, 118, 121, 315

Hulls, see shells

Humphrey, N., 317

Hunn, C. J., 209

Hunt, N. Rex., 317

Hunter, J. H., 116, 323

Husted, L., 71, 85

Hutcheson, T. B., 167

hypocotyl, morphology of, 36-38, 39

industry, peanut, development in United
States, 6-15

Indian meal moth, 245-246

Indians, use of peanuts by, 5, 6, 9, 19-22,
25

inflorescence, morphology of, 48-49, 62

inheritance studies in breeding, 77-79

inoculation of seed, 99, 194-196. See also
diseases

insect pests, 157, 198, 210-250, 312

insecticides, see insect pests

Ireland, C. F., 150, 171

iron, 104-105, 108, 311. See also nutrition

Isely, Dwight, 226, 250, 255

Ivanoff, S. S., 317

Jackson, A. M., 116
Jacobs, W. P., 52, 85, 98, 100, 118
Jarvis, E., 247, 255
Jefferson, Thomas, 6, 16
Jenkins, A. E., 314
Jenkins, W. A., 274, 317
Jenny, H., 101, 118
Jensen, J. S., 293, 317
Jochems, S. C. J., 317
Jodidi, Samuel L., 109, 119
John, C. M., 61, 85, 86
Johnson, C. M., 167

Jones, B. W., 135, 169
Josselyn, 16

Kehring, H., 255

KenkKnight, G., 293, 299, 300, 317-318

Kerle, W. D., 131, 169

Kerr, J. A., 169

Khanna, Kidar Lal, 119

Killinger, G. B., 111, 119, 124, 169, 186
209

King, George H., 209

Krauss, F. G., 131, 169

INDEX

Krieger, H. W., 26
Kurtz, F., 48, 59, 85
Kushman, L. J., 71, 85
Kyzer, E. D., 209

Labat, R. P., 25, 26

Lacroix, D. S., 255

Lane, M. C., 255

Langley, B. C., 169

Laphygma frugiperda, 216-221

Larsh, H. M., 318

Larter, L. N. H., 318

leafhopper, potato, 106, 198, 225-230,
231, 240, 312

leafspot, 80, 114, 198, 226, 229-230, 262,
271-277, 303, 310

Leagy, J. F., 323

Lean, O. B., 256

Leary, Jean de, 21, 26

leaves, morphology of, 46-47

Leefmans, S., 256

Legleu, R., 295, 320

Leukel, W. A., 172

Lever, R. J. A. W., 256

light relations, 98

lime, see calcium

limestone, see calcium

Line, C. W., 318

Lipscomb, R. W., 318

Littig, K. S., 257

Liu, 100 *

Livingstone, E. M., 253, 256

Loehwing, W. F., 119

Long, David D., viii

Lou, 100

Luginbill, Philip, 217, 256

Lush, R. H., viii

Luttrell, E. S., 318

Lyle, Clay, 256

Lyne, W. H., 256

' MacClenny, W. E., 16

Macfarlane, Wallace, viii

machinery, 8, 196-197, 199-203, 207

Mackie, D. B., 256

Macrophomina, 305

magnesium, 104, 107, 108, 311. See also
mineral nutrition

maintenance of soil fertility,
See also fertilization

manganese, 106, 108, 311. See also min-
eral nutrition

Mann, H. B., viii, 141, 169

Marchionatto, J. B., 318

155-163.

329

Marggraf, Georg, 28, 85

Marin, L., 170

Marmor arachidis, 295

Marsh, H. O., 256

Martenet, R. D., viii

Mason, C., 256

Massibot, J. A., 132, 170

maturation diseases, 282-284

Maublanch, A., 318

Maximov, Nicolai A., 119

McClean, A. P. D., 318

McClelland, C. K., 129, 137, 151, 169,
179, 209

McClintock, J. A., 318

McCoy, E. E., 254

McDonald, J., 318

McGregor, E. A., 258

McLaughlin, J. H., 317

McNess, George T., 209

McVickar, M. H., viii

Meagher, W. R., 121

Mehlich, A., 119, 146, 147, 148, 170

Mendes, A. J. T., 71, 72, 86

Merkl, Marvin E., 222, 256

metabolism, carbohydrate and nitrogen,
99

Metcalf, C. L., 256

Metcalf, Z. P., 106, 119, 226, 256, 312,
318 ;

Meyer, Bernard S., 119

Middleton, G. K., 94, 108, 119, 153, 154,
170

Miller, D., 256

Miller, Edwin C., 89, 119

Miller, F. E., 209

Miller, J. H., 303, 304, 307, 318

Miller, Lawrence I., 106, 119, 120, 185,
209, 229, 256-257, 258, 272, 275, 276,
318-319, 321

Miller, P. R., 319

mineral composition, 106-112

mineral nutrition, 47, 89-115, 122-166,
310-311

Mohammad, Ali, 90, 96, 119

Mohr, H. C., 316 7

molybdenum, 106, 108. See also mineral
nutrition

Monardes, N., 20, 26, 28, 86

Moore, Rufus H., 98, 99, 109, 111, 112,
119

Moore, W. D., 319

morphology, 28-88

Morris, H. D., 111, 117, 150, 168, 170

Morwood, R. B., 319

330

Moser, F., 170

Moses, D., 131, 170
Murneek, A. E., 119
Murray, G. H., 170
Murray, Mildred D., 120
Mycosphaerella, see leafspot

names, vernacular, for peanuts, 6, 7,
19-20

National Fertilizer Association, vii, viii

Naude, T. J., 257

Neal, P. A., 253

Neisler, Hugh M., 58, 86

Nelson, R. H., 257

Nelson, W. L., 122, 137, 149, 170, 171

nematodes on peanuts, 307-309

Newman, L. J., 257

Nicholson, G., 172

nitrogen, 103, 107, 108, 128-131, 154,
163-164, 311. See also metabolism;
nutrition

nonpathogenic diseases, 310-312

Nowell, W., 319

Nusbaum, C. J., 319

nutrition, mineral, 47, 89-115, 122-166,
310-311

nutritive value, 14, 108-109

O'Brien, R. E., 132, 170

O’Conner, Robert T., 120

Okuni, T., 247, 257

origin and early history, 18-27

Oryzaephilus, 246

Osterberger, B. A., 215

Overstreet, R., 101, 118

Oviedo y Valdés, Gonzalo Fernandez de,
20, 26, 28, 86

oxygen requirements, 97

oyster shells, 138. See also calcium

Paden, W. R., 170

Padget, L. J., 254, 257

Page, N. R., 111, 113, 117, 119
Painter, R. H., 224, 260

Palm, B. T., 319

Panse, E., 319

Pantomorus leucoloma, 235-240
Parham, S. A., 124, 170, 186, 209
Parker, F. W., viii

Pate, W. F., 131, 170

Patel, J. S., 74, 77, 78, 80, 86, 119
Paulette, J. C., 16

Paulino, P. L., 84, 86

peanut butter, 5, 8, 9, 14-15

INDEX

peanut oil, 3, 5, 6, 8, 9, 12, 71, 108-110

Peanut Research Committee, viii

Peech, M., 169, 171

pegs, morphology of, 51-53, 58; phy-
siology of, 91-93; mineral com posi-
tion of, 111. See also diseases

Penicillium, 264, 270, 283, 287, 312

pests, see insect pests

Peterson, M. J., 124, 168

Pettit, A. S., 33, 48, 53, 86, 96, 119

Philips, M. W., 16

Phillips, W. J., 222, 257

phosphorus, 103, 107, 108, 131-132, 163,
311. See also mineral nutrition

photosynthesis, 99

Phyllosticta, 303

Phymatotrichum, 302

physiological diseases, 310-312

physiology, 89-115

Pickett, T. A., 116, 118, 120

picking, see harvesting

Pierre, W. H., 170, 171

Pigafetta, Antonio, 23, 26

Piland, J. R., 117, 150, 171

Pinkard, J. A., 319

Piroznikova, M. F., 81, 86

Plant Food Research Committee of the
National Fertilizer Association, vii,
viii

planting, 173-187

Pliny, 18, 19

Plodia inter punctella, 245-246

pods, morphology of, 53-54, 58. See also
diseases

Poiteau, M., 28, 58, 86

Pole-Evans, I. B., 319

Pollock, N. A. R., 171

Pons, Walter A., Jr., 101, 120

Poole, R. F., 316, 319-320

Poos, F. W., 226, 227, 228, 229, 235, 251,
254, 257

Popenoe, C. H., 245, 246, 248, 258

Porteres, R., 295, 320

post-emergence damping off, 266-267

potash, see potassium

potassium, 103-104, 107, 108, 133-135,

163-164, 311. See also mineral nutrition

potato leafhopper, 106, 225-230, 231,
240, 312

pouts, 226, 231, 312

pre-emergence diseases, 263-266

Prevot, Pierre, 45, 46, 70, 86, 128, 171

Prince, Alton E., 120, 320

production figures, 3-7, 9-15

INDEX

Purswell, Henry D., 211, 215, 258
Pussard, R., 258
Pythium, 264

Quaintance, A. L., 222, 258
quicklime, see calcium
Quinn, H. G,, 171

Ramakrishna, A. T. U., 258

Ramsey, David, 6, 16

Ray, W. Winfred, 317

Rayss, T., 320

Reddi, K. K., 120

Reed, Edward L., 33, 47, 54, 86, 96, 120

Reed, J. Fielding, 116, 119, 120, 122, 137,
146, 148, 168, 170, 171, 190, 209

Reed, W. D., 258

Reeves, W. A., 118

Reichert, I., 320

Reisenauer, H. M., 150, 171

reproductive morphology, 28, 48-59

Reyes, G. M., 80, 86, 320

Reynolds, E. G., 169

Rhind, D., 320

Rhizoctonia, 243, 267-268, 270, 271, 283,
287, 309

Rhizopus, 264, 270, 283, 312

Rhoads, Arthur S., 320

Richard, Achille, 28, 86

Richter, Curt Georg, 29, 33, 36, 46, 47,
49, 53, 54, 55, 56, 62, 86

Rigney, J. -\., 87

Robinson, H. F., 76, 87

Robinson, J. M., 217, 242, 258

Rodrigo, P. A., 75, 87

Roepke, W., 247, 258

Rogers, H. T., 120, 137, 138, 145, 146,
171

Rohwer, G. G., 236

Romasanta, R., 80, 86

root, morphology of, 33-37, 43-45; phy-
siology of, 94-97; mineral composi-
tion of, 111

root hairs, see roots

root knot, 307-309

root rot, 302, 303-304

rootworm, southern corn, 240-242, 244

rosette, 262, 293-297

rotation and management practices,
155-163, 165

rots, see diseases

Raubaud, E., 247, 258

Russell, M. W., 53, 87

rust, peanut, 299-301

331

Sahagun, Bernardino de, 21, 26

Sandu-Ville, C., 320

Savelescu, T., 320

Sayers, R. R.,. 253

Scab, Sphaceloma, 301

Schmehl, W. R., 171

Schmidel, Ulrich, 28, 87

Schultz, E. F., 45, 75, 84, 119, 153, 170,
172

Schwartz, M. B., 320

Schwitzgebel, R. B., 253

Sclerotinia blights, 304-305

Sclerotium blight or rot, 80, 128, 157, 198,
264, 267-269, 270, 277-282, 283-284,
287, 289-290, 305

Seal, J. L., 321

seed and seedling, morphology of, 29-33,
42, 54-55, 58; mineral composition
of, 108-110; soil rot of, 263-266. See
also diseases

seed per acre, 186-187

seed preparation and treatment,
194, 264-266

seedling, see seed and seedling

Sell, H. M., 117

Sellars, O. H., 168

Sellschop, J. P. F., 131, 170, 171

Seshadri, C. R., 61, 85, 86, 119

Sessions, L. H., 17

Shaw, Luther, 209, 320-321

Shchegolev, V. N., 258

Shear, G. M., 106, 120, 149, 171, 258, 321

shelled vs. unshelled seed, 187-190, 264-
265

shelling, methods of, 189-190, 265. Se
also seed preparation and treatment

shells, mineral composition of, 110-111

Sheppard, R. A., 258

Sherbakoff, C. D., 321

Shibuya, T., 52, 87, 91, 93, 97, 99, 120

Shive, J. W., 120

Shull, A. F., 258

Simmons, P., 258

Skinner, J. J., 171

Slime disease, see Bacterium solunacearum

Sloane, Hans, 24-25, 26

Small, W., 321

Smalley, H. R., viii

Smith, Ben W., 28-83, 87

Smith, C. E., 259

Smith, T. E., 321

Smyth, E. G., 259

soil, preparation of, 173-174; properties
of, 122-125, 145-148

187-

332

soil fertility, 109, 122-166. See also
fertilization

soil insects, 240-245. See also white-
fringed beetle

soil rots, 263-266, 282-284, 309, 312. See
also Sclerotium blight -

Sommer, Anna L., 120, 121, 150, 171, 321

Soriano, S., 321

South, F. W., 321

southern corn rootworm, 240-242, 244

southern root rot, see Sclerotium blight

Souza, Gabriel Soares de, 21

Soyer, D., 321

Spacing of plants, 178-186

Speairs, R. K., 321

Species of peanuts, 59-70

Sphaceloma scab, 301

Squier, E. G., 19, 27

stacking, 187, 200, 204-207. See also
harvesting

Stahl, A. L., 120

Stanford, E. E., 321

Stansbury, Mack F., 118, 121

Stansel, R. H., 121, 172, 209

Staten, H. W., 110, 117

Steiner, G., 309, 321

stem, morphology of, 36-37, 45-46

Stewart, M. A., 259

Stokes, W. E., vii, 74, 77, 78, 81, 87, 100,
119, 121, 153, 169, 172, 209

Stone, G. M., 321

storage, 187, 208; insect pests, 210-261;
diseases, 290-292

Storey, H. H., 293, 294, 295, 322

Stout, P. R., 121

Strauss, J. L., 121

Strong, L. A., 239, 259

Stuckey, H. P., 172

Sturkie, D. G., 172, 173-208, 209

Su, M. T., 322

Suematu, N., 304, 305, 322

sulfur, 104, 106, 107, 108, 276, 281, 299,
311. See also mineral nutrition

Sundararaman, S., 322

Swain, R. B., 239, 259

Swank, G. R., 256

Sweetman, H. L., 259

Tang, P. S., 100

Taubenhaus, J. J., 322

Taubert, P., 59, 60, 87

Taylor, C. F., 322

Taylor, J. R., viti

techniques of breeding peanuts, 73-76

INDEX

temperature relations, 98
Tenebroides, 247

Theophrastus, 18

Theune, Erich, 52, 71

Thomas, K. M., 322

Thompson, Helen H., 121, 260, 323
Thompson, J. M., 53, 87
Thornton, G. D., 121

thrips, tobacco, 74, 106, 230-235, 312
Timson, S. D., 172

Tisdale, H. B., 178, 209

Tisdale, W. B., 116, 118, 169, 322
Tissot, A. N., 118, 169

tobacco thrips, see thrips
Tribolium, 246-247

Umen, D. P., 74, 81, 83, 87

United States, development of peanut
industry in, 6-15

Utt, C. A. A., 9, 17

Valdivia, M. A., 172

Van der Goot, P., 322

Van der Stok, J. E., 70-71, 77, 80, 87

Van der Volk, P. C., 102, 121

Vanselow, A. P., 121

variability in peanuts, 59-70

varietal differences in response to fertili-
zation, 151-155, 165

varieties of peanuts, 60-70

Vaughan, E. K., 322

Vayssiere, P., 259

Vega, Garcillosa de la, 20

vegetative structure of mature peanut
plant, 43-47

velvetbean caterpillar, 198, 210-216

Verrill, Alpheus, 27

viability, see germination

Vickery, R. A., 220, 259

Vidal, R., 132, 170

virus diseases, 293-297

Volk, N. J., vii

Wadleigh, C. H., 121

Waldron, R. A., 23, 27, 33, 34, 52, 53,
88, 96, 121, 172

Walkden, H. H., 253

Walker, H. G., 251

Wallace, C. R., 259

Wallace, R. W., 322

Ward, H.S., Jr., 311

Warner, J. D., 116, 119, 169, 209, 314

water requirements, 97

Watkins, G. M., 323

INDEX

Watson, J. R., 211, 212, 213, 215, 230,
259-260

Watson, Sir William, 6, 17

Watts, J. G., 260

Wear, John I., 121, 171

Weigel, C. A., 257

Weiss, F., 295, 323

Weiss, H. B., 260

Wenholz, H., 172

West, E., 300, 323

West, H. O., 121, 129, 171, 209

Wheeler, C. D., 118

white-fringed beetle, 235-240

Williams, John Lee, 7, 17

Williamson, J. T., 168, 173-208

Wilson, Coyt, 114, 121, 189, 190, 191,
209, 216, 260, 262-313, 321, 323

Wilson, J. P., 260, 323

wilt, bacterial, 262, 297-299; Fusarium,
303-304. See also blights

Winburn, T. F., 224, 260

Wingard, S. A., 209, 323

333

Winston, J. R., 316

Winton, Andrew L., 9, 17, 121

Winton, Kate B., 121

wireworm, 241, 242-243

Wisecup, C. B., 260

Wolf, F, A., 321, 323

Wolk, P. C., 172

Woodroof, J. G., 121, 260, 272, 274, 276,
291, 323

Woodroof, Naomi C., 323

Woronichin, N. N., 323

Yarbrough, John A., 28-83, 88
York, E. T., Jr., 122-166, 172
Young, H. C., 237, 260-261
Yu, T. F., 324

Zacher, F., 261

Zimmerman, A., 324

zinc, 106, 108, 311. See also mineral nu-
trition

24
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