DISE ASES OF TRUCK CROPS
AND THEIR CONTROL
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DISEASES OF TRUCK CROPS
AND THEIR CONTROL
OTHER WORKS
BY THE SAME AUTHOR
The Culture and Diseases of
the Sweet Pea - $2.00 net.
Profusely Illustrated
Diseases of Greenhouse Plants
(In Preparation)
Diseases of the Sweet Potato
(In Preparation)
E. P. DUTTON & COMPANY
NEW YORK
Sor.
DISEASES OF TRUCK CROPS
AND THEIR CONTROL
BY
J. J. TAUBENHAUS, Pu.D.
Plant Pathologist and Physiologist to the Agricultural and Mechanical
College of Texas
Author of ‘‘ Culture and Diseases of the Sweet Pea’’
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681 FIFTH AVENUE
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Copyright, 1918
By E. P. DUTTON & COMPANY
PRINTED IN THE UNITED STATES OF AMERICA
To uy FRIEND ?
B. KACZER
PREFACE
THE world never has faced a greater shortage of
food than to-day. War’s destructive agencies have
added themselves to our old invisible foes, namely
parasitic and disease-producing bacteria and fungi.
More than half of our diet is made up of vege-
tables. They furnish the necessary food bulk which
the body requires, supply important nutritive ele-
ments, and act as stimulants to a better blood circu-
lation. According to the Thirteenth Census of the
United States the area devoted to truck crops in the
United States in 1909 was estimated at 7,436,551
acres. The total money value of the truck crops
grown on this acreage was estimated at $301,104,144.
The crops thus estimated included asparagus, beans
(green), beans (dry), beets, cabbage, cauliflower,
corn (pop and sweet), cantaloups, carrots, celery,
chicory, cucumbers, egg plant, horse-radish, kale,
lettuce, mint, okra, onions, parsley, parsnip, peas
(green), peas (dry), peppers, pumpkin, radish,
rhubarb, rutabagas, spinach, sprouts, squash, sun-
flower, sweet potato and yam, tomatoes, turnips, and
watermelon.
We scarcely realize the large sums of money which
the trucker loses annually from specific plant dis-
eases, because there are few available data as to
Vii
Vili Preface
the money losses. But as an example, the following
figures, kindly given to the writer by Professor R. P.
Haskell, Pathological Inspector of the United States
Department of Agriculture, will be of compelling
interest.
“Potato Diseases.—It is estimated that the State
of New York lost in 1915, principally from late
blight, about $20,000,000. This outbreak was wide-
spread in the northern States and reduced the yields
as shown below, in comparison with 1914. Other
conditions than disease were relatively equal:
Maine 10,000,000 bu.
New Hampshire 1 200:G00.57,
Vermont 1,600,000 “‘
New York 30,000,000 “‘
Pennsylvania 8,000,000 “
Michigan 23,000,000 “‘
Wisconsin 11,700,000 ‘
“Tt is estimated that the market value of the
potato crop in Aroostock County, Maine, in 1915
was reduced about 10%, or $1,078,000, on account of
the occurrence of the powdery scab disease. In
some sections the reduction amounted to as much
as 50%.
“It is estimated that 50% of the potato crop in
Idaho was injured by diseases last year and from 10%
to 20% rendered wholly unsalable. The total an-
nual loss in this State is estimated at $196,000.
“ Sweet-Potaio Diseases.—It is estimated that the
annual loss due to sweet-potato diseases in the
.
Preface ix
United States is approximately $10,000,000. About
$750,000 of this loss may be attributed to stern rot,
the other important diseases being black rot, foot
rot, and storage rots.
“Asparagus Rust.—Asparagus rust has practically
destroyed all of the original plantings of asparagus
and driven the old varieties out of cultivation. These
have now been replaced by partially resistant kinds
and the new strain bred by this Department is almost
wholly resistant, so that in the near future these
losses will be eliminated. Tests of some of the new
rust-resisting strains in 1915 showed gains over the
standard varieties amounting to more than $200
per acre.
“Cowpea Diseases.—It is estimated that the an-
nual saving as a result of the introduction of wilt
and root-knot resistant cow-peas is $3,000,000.”
A conservative estimate of the money loss from
diseases would be about 20% of the total value of
the truck crops grown in the United States. Accord-
ing to the estimate given on page vii, the total value of
the truck crop in the United States in 1909 amounted
to the sum of $301,104,144. If 20% of this was lost
through damage from diseases, it will be seen that
in I909 the American truckers lost $60,220,828.
This does not include the large losses from insect
pests, nor losses incurred in storing, or in shipping
truck produce.
It is no exaggeration to state that if our present
knowledge of Plant Pathology were made use of by
truck farmers, nearly 80% of this loss could be
x Preface
prevented. Can any one say that such a saving
would be insignificant, untimely, or unpatriotic?
The present work has been prepared with the aim
of stimulating more research in truck-crop diseases,
and also of assisting the trucker to make use of our
present knowledge, in order to prevent avoidable
losses, increase the trucker’s profits, and assure a
greater food supply. The writer seriously solicits
suggestions or criticisms on his work.
Acknowledgments are due to Dr. and Mrs. D. de
Sola Pool, of New York City, for the inspiration, the
encouragement, and the valuable assistance rendered
in the preparation of the manuscript, and later in
reading and criticizing it. To Dr. E. A. Bessey of
the Michigan Agricultural College, and to Dr. Mel.
T. Cook of Rutgers College, the author owes hearty
thanks for the careful reading and the valuable
suggestions and criticisms which they have given this
work. Acknowledgments are also due to Dr. G.
H. Coons of the Michigan Agricultural College, to
Prof. F. B. Paddock and to Mr. W. T. Brink of the
Texas Agricultural Experimental Station for reading
the manuscript and proof. Grateful appreciation is
likewise due to Dr. I. Adlerblum of the Metropolitan
Life Insurance Co. of New York City for criticizing
the manuscript and proofs.
For the use of illustrations the author is indebted:
to Dr. G. P. Clinton; to Dr. Mel T. Cook; to Drs.
G. H. Coons and E. Levin; to Dr. H. A. Edson; to
Dr. B. B. Higgins; to Prof. H. S. Jackson; to Dr. L.
R. Jones; to Dr, T. F. Manns; to Prof. A. V. Osmun;
Preface xi
to Prof. F. B. Paddock; to Prof. W. G. Sackett; to
Prof. A. D. Selby; to Prof. R. E. Smith; to Prof. H.
E. Stevens; to Prof. J. A. Stevenson; to Prof. D. B.
Swingle; to Prof. DeVault and to Dr. F. A. Wolf.
Last, but not least, grateful acknowledgments are
due my wife Esther Michla Taubenhaus, whose de-
votion to art and science, and whose inspiration made
this work possible.
J. J. TAUBENHAUS
COLLEGE STATION, TEXAS
January 22, 1918.
PREFATORY NOTE
WitH the greater specialization along all lines of
industry the problems that confront such a specialist
as the author of this book are felt more keenly and
the necessary remedies are more fully appreciated.
So there has grown up in the last few decades in
this country a body of agricultural experts, the
truck growers, who have found, as they have con-
centrated their attention more and more inten-
sively upon a limited number of crops, that they
are paying a great tax in the shape of losses due
to diseases. Probably, in fact we know that very
often it certainly is the case, similar losses are
suffered by general farmers, but with their large
plantings and less intensive culture these losses are
not appreciated as they are by the truck grower.
Other factors, too, enter in. In general the truck
crops occupy land near cities or which from its
adaptability to special crops or from its accessibility
to markets is accordingly more valuable than ordinary
farm lands. Furthermore, the crops themselves
have a greater monetary worth than the staple
crops. Both these factors make the losses by plant
diseases much more keenly felt. With this recogni-
tion of the losses incurred has arisen a demand for
Xili
xiv Prefatory Note
help in the prevention of the diseases responsible
for the damage. So plant pathologists have had to
direct their attention to diseases of truck crops.
The present book is an attempt by such a pathologist
who has specialized along this line to meet the de-
mand for help in the way of giving information as
to the diseases occurring on truck crops and, so far as
it is possible, telling how these losses may be pre-
vented or at least reduced.
The last quarter century has seen a marvelous
development of that division of the science of Botany
that is devoted to the study of plant diseases, Plant
Pathology. As each crop has been given greater
attention the number of diseases found to occur
upon it has been amazing. Plants nearly related
to each other may have some of their diseases in -
common, but even with very closely related species
some of the troubles affecting them will be different.
When we now consider the large. number of crop
plants that are the subject of intensive culture as
truck crops, and note, furthermore, that they re-
present the most diverse families of plants, it is not
to be wondered at that the number of organisms
causing diseases of truck crops is a large one. The
author by grouping the crop plants together by their
botanical affinities has taken full advantage of the
fact that nearly related plants may suffer from some
of the same diseases and thus has made it possible in
some cases to consider such diseases only once for
several different, but closely related, crops.
Considerable attention is directed to the symptoms
Prefatory Note XV
by which the various diseases may be distinguished.
These descriptions are made in non-technical lan-
guage so that the practical grower can understand
them and recognize the diseases in question. Besides
this the methods of control are also described in popu-
lar terms. The author’s long study of the subject has
made it possible for him to approach this part of the
work from the standpoint of the grower, so that as
far as possible the remedies or preventive measures
recommended are those with which he has practical
experience. Occasionally it is impossible to recom-
mend a remedy since sometimes a disease is of such a
nature that by the time it becomes apparent the
damage is done. But even in such cases directions
are given which will reduce the loss or at least
permit its avoidance another season. The discus-
sions as to the cause of the disease are unavoidably
given in somewhat more technical form from the
very nature of the case, especially where it is the
question of diseases caused by fungi or bacteria
for which brief scientific characterizations are neces-
sary. These technical discussions are essential for
pathologists and other students of the subject so
that the book will be appreciated by Experiment
Station workers, Extension Specialists, college stu-
dents, and others, as well as by the truck growers
themselves for whom the book is primarily intended.
ErRnsT A. BESSEY,
_ Professor of Botany,
Michigan Agricultural College.
CONTENTS
PART I
CHAPTER I
THE NORMAL SOIL AND ITS REQUIREMENTS
CHAPTER II
SicK SOILS NOT INFLUENCED BY PARASITES
CHAPTER III
SoIL SICKNESS DUE TO THE PRESENCE OF PARA-
SITES HARMFUL TO PLANTS
CHAPTER IV
METHODS OF TREATING SICK SOILS . A
PART. If
CHAPTER V
THE HEALTHY HOST AND ITS REQUIREMENTS
CHAPTER VI
CAUSES OF DISEASES IN CROPS
A. Diseases of a Mechanical Nature
B. Diseases Due to Physiological Causes
c. Diseases of Unknown Origin
XVil
PAGE
23
AI
a3
63
71
XVili Contents
PAGE
D. Diseases Due to Parasitic Bacteria or Fungi
E. Diseases Induced by Parasitic Flowering
Plants
CHAPTER VII
Poor SEED : ‘ : . ; ‘ - ie ge
PART Ag
SPECIFIC DISEASES OF TRUCK CROPS
CHAPTER VIII
FAMILY AGARICACE : : } x 4 Os
Diseases of the Mushroom
CHAPTER IX
FAMILY ARALIACEA : : ; Goh ae? VL Oe
Diseases of the Ginseng
CHAPTER X
FAMILY CHENOPODIACEZ . : : : - > Li6
Diseases of the Beet
Diseases of the Spinach
CHAPTER XI
FAMILY COMPOSITE . ; : : : RRS ter
Diseases of the Artichoke (Jerusalem)
Diseases of the Artichoke (Globe)
Diseases of the Lettuce
Diseases of the Salsify
Diseases of the Sunflower
Contents
CHAPTER XII
FAMILY CONVOLVULACE4 :
Diseases of the Sweet Potato
CHAPTER XIII
FAMILY CRUCIFERE .
Diseases of the Cabbage
Diseases of the Cauliflower
Diseases of the Horse Radish
Diseases of the Kale
Diseases of the Mustard
Diseases of the Radish
Diseases of the Turnip
CHAPTER XIV
FAMILY CUCURBITACE
Diseases of the Cantaloupe
Diseases of the Cucumber
Diseases of the Citron
Diseases of the Squash
Diseases of the Watermelon
CHAPTER XV
FAMILY GRAMINE
Diseases of the Sweet Corn
CHAPTER XVI
FAMILY LABIATZ :
Diseases of the Balm
Diseases of the Catnip
Diseases of the Horehound
xix
PAGE
I5I
185
218
255
XX Contents
~Diseases of the Mint
Diseases of the Peppermint
CHAPTER XVII
FAMILY LEGUMINOS
Diseases of the Bean
Diseases of the Lima Bean
Diseases of the Cow Pea
Diseases of the Garden Pea
CHAPTER XVHI
FAMILY LILIACEZ
Diseases of the Asparagus
Diseases of the Chive
Diseases of the Onion
CHAPTER XIX
FamMILy MALVACE4
Diseases of the Okra
CHAPTER XX
FAMILY PORTULACACEZ
Diseases of the Purslane
CHAPTER XXI
FAMILY SOLANACEZ .
Diseases of the Egg Plant
Diseases of the Pepper
Diseases of the Potato
Diseases of the Tomato
PAGE
259
279
299
300
Contents — XXi
CHAPTER XXII
FAMILY UMBELLIFERE U : : , ess io)
Diseases of the Carrot
Diseases of the Celery
Diseases of the Parsley
Diseases of the Parsnip
Weeds
PART: EV
CHAPTER XXIII
METHODS OF CONTROL : ; : : Be ie te |
CHAPTER XXIV
- CONTROL OF INSEcT PESTS By NATURAL FACTORS 375
CHAPTER XXV
TREATMENT OF FENCE Posts . : i bape eis
GLOSSARY : : : : : ; Seed
TMBEX ||: : : % ; ; Pee 3 7,
FIG.
Olas Tactics ee erty yeah
‘o
10.
i.
13.
14.
ILLUSTRATIONS
PAGB
BACTERIA : : p . : : 4
STRUCTURE OF FUNGI : ; : TODA SE
NITRE-SICK BEET FIELD, SHOWING BARREN
Spots . : ; : : : Sha ees
EFFECT OF LIME 3 : : : et 2g
PYTHIUM DEBARYANUM P : eae
RHIZOCTONIA . : , 5 L eens
FusARIUM WILT : : : : Renae
NEMATODE Root KNOT. i , TAU (2
INVERTED PAN FOR STEAM STERILIZATION 55
SURFACE WATERING, SHOWING PORTABLE
SPRAY EQUIPMENT USED IN GARDENS ABOUT
CoLp FRAMES AND HOTBEDS : Be eae
WATERMELON SLICE SHOWING Halt INJuRY 74
LIGHTNING INJURY IN. POTATO FIELD.
DrouGHT INJURY OF SWEET CORN My fe,
MALNUTRITION, SHOWING A CABBAGE LEAF
AFFECTED BY THE DISEASE . A 5 8I
BLossom Drop : : - : Seren sc}
xxiii
xxiv Illustrations
FIG. PAGE
15. Mosaic . : : : : 5 VRE Rs 32 i 202
16. BEAN SEEDS AFFECTED WITH ANTHRACNOSE,
Colletotrichum lindemuthianum . : aie)
Py. WOpDER = : é : : : 0708
18. MycoGonE DIsEASE OF MUSHROOMS . . Os
19. GINSENG DISEASES . ° : : + -£09
20. BEET DISEASES : A 3 : sy FBO
21. SPINACH DISEASES . ‘ ; ; at Ee
22. LrETTucE Drop : : ; : So ae
23. LETTUCE DISEASES . ‘ ; : sa.
24. SOUTHERN BLIGHT OF THE SALSIFY . ae)
25. SWEET POTATO DISEASES . 5 : = 52
26. SWEET PoTaTo DISEASES... : lS
27. SWEET PoTATO DISEASES . f : ents {> 6
28. SWEET POTATO DISEASES . 4 : : 170
29. SWEET POTATO STORAGE HOUSES : notes
30. CABBAGE DISEASES . 1 : ! SB oh
31. CABBAGE DISEASES . é : : a? 106
32. CABBAGE DISEASES . F d 4 Lc i98
33. DISEASES OF THE CAULIFLOWER AND RADISH 202
34. CERCOSPORA LEAF SpoT OF HoRSE-RADISH . 207
35. RADISH DISEASES . : : : i ae
FIG.
36.
37:
38.
39.
40.
4I.
42.
43.
44.
45-
46.
47-
48.
49.
50:
SE:
52.
53-
54.
55-
56.
57:
Illustrations
TurRNIP DISEASES . 3 : P ‘
TuRNIP DISEASES . Y : é s
CANTALOUP DISEASES
RESISTANT CANTALOUP STRAIN .
CUCUMBER DISEASES.
SQUASH DISEASES
WATERMELON DISEASES
WATERMELON ANTHRACNOSE
WATERMELON DISEASES
SWEET CoRN DISEASES
BEAN DISEASES : ;
BEAN DISEASES
DISEASES OF LIMA BEAN .
BEAN DISEASES
DISEASES OF THE Cow PEA
DISEASES OF THE GARDEN PEA AND BEAN.
ASPARAGUS DISEASES ‘
ONION DISEASES : :
ONION DISEASES ;
DISEASES OF THE OKRA . :
EGGPLANT DISEASES : : ‘
DISEASES OF THE PEPPER
PAGE
215
217
221
228
230
235
239
241
244
251
260
262
267
269
272
274
280
285
286
296
302
395
xxvi Illustrations
FIG. PAGE
58. Potato DISEASES . ’ : rf . 308
59. DISEASES OF THE POTATO 4 : eS
60. Pox or PIT OF THE WHITE POTATO, SHOWING
DIFFERENT STAGES OF INFECTION . PND
61. POTATO DISEASES . : : : Pranic
622) POTATO: DISEASES.:<. : : , ges
63. PoTATO DISEASES . : i 2 heat
Gi) GhOMATODISHASES 4) i ))\Gus : : wi sao
65. TOMATO DISEASES . : J 246
66. TOMATO DISEASES. : : ; Mo 3
67.) TOMATO DISEASES. k : 4 +S SSE
68. SLEEPING SICKNESS OF TOMATO : . 352
69. CELERY DISEASES : : , : Ona 56
70. CELERY DISEASES ... ‘ ‘ : g57
71. SPRAY MACHINERY . Ny é igre
72. PARASITIZED INSECTS. TREATMENT OF FENCE
Posts. é A : : : 378
INTRODUCTION
THE present world crisis has suddenly transposed
the farmer from his former modest and humble posi-
tion into the ranks of our foremost national figures.
To-day the services of the tiller of the land are at
a premium. The heroes of the day are not only
those who can shoulder a gun at the front, but also
those who can produce the food necessary to feed the
great civil and military armies in the field and at
home. It is to the credit of the American people
that they have realized that intelligent farming re-
quires as much skill, thought, and energy as 1s re-
quired to build up industries or to formulate laws of
government.
Of the many phases of agriculture, trucking be-
longs to the highest forms of intensified farming.
Whether it is conducted on a large or on a small
scale, it requires a thorough knowledge of plant life.
An intelligent understanding of crop rotation is
essential for success. Someone has well said that
the farmer may be judged intellectually by the system
of rotation which he practices. Great skill is also
required to keep the land in a state of production
during the greater part of the year. This is espe-
cially true for our Southern States. As a whole,
5 XXVI1l1
XXviii Introduction
therefore, successful truckers must be a highly intel-
ligent class of agriculturists.
In trucking, as in all intensive farming, the aim is
to produce superior crops, embodying both high
yield and good quality. This can be made possible
only through intensive breeding and culture. Un-
fortunately, however, improvement in quality and
yield is often accompanied by a loss of natural
vigor and of power of resistance to disease. The
great problem of the trucker is twofold—that of
striving for quantity and quality, while protecting
his crops from disease. This latter phase has gener-
ally been overlooked. We all realize to-day that it
is necessary not only to produce two blades of grass
where one grew before, as Dean Swift declared, but
also to conserve it during growth and prevent it from
being carried off by various diseases. The great fam-
ine in Ireland in 1844 resulted from an epidemic of
late blight which destroyed the potato crop. Sucha
condition could hardly occur to-day, because we now
havea better knowledge of plant life, the causes which
induce disease, and the methods of coping with it.
Considerable research has been carried out on the
diseases of truck crops. The work of Professors Stew-
art, Selby, Jones, Orton, Clinton, Lutman, Melhus,
Manns, Harter, Sackett, Whetzel, and of others has
already yielded valuable information on the diseases
and their control in the case of some of our staple
food crops. Still, in the case of many diseases, little
is known as yet as to methods of treatment. But
much is to be looked for from research in the future.
Introduction Xxix
It was the writer’s intention to avoid technical
terms as far as possible. However, it was found ex-
tremely difficult to omit every trace of a technical
vocabulary, inasmuch as the popular terms are not
always adequate in identifying a disease or in de-
scribing its causal organism. As far as was consistent
all popular names were accepted and retained in this
work. However, there are many diseases which
have as yet no popular names. As an illustration
may be mentioned certain spot diseases of particular
hosts. These spots may be caused by different fungi
and yet resemble each other. In such a case how are
we to name these diseases? The surest way to avoid
confusion is to call the diseases by the name of the
causal organism, such as Phyllosticta leaf spot, Cer-
cospora leaf spot, etc. Professor Stevens has sug-
gested that we name all diseases by the name of their
causal organism and add to it the term ‘“‘ose,’’ such
as Phyllostictose, Cercosporose, Sclerotinose, etc.
The writer has not adopted Stevens terminology.
In many cases the popular name of a disease de-
scribes it far better than a technical term cando. To
drop altogether such valuable popular terminology
would only confuse the practical man. For instance,
the popular term for lettuce ‘‘drop”’ is far more sug-
gestive than ‘‘Sclerotinose.’’
From a practical consideration, the healthy plant
is of greater importance than the disease. If we were
to bend all our energy and skill to safeguarding the
health of our crops, we would not be pestered with
diseases. This is the point of view of this work.
XXX Introduction
For this reason, too, much space has been given to a
consideration of the healthy hosts and of the soil, the
mother of all vegetation.
For the sake of convenience, the crops here con-
sidered have been taken up in the natural order of
families to which they belong. The families have
then been arranged in alphabetical order, and the
crops in each family taken up alphabetically by their
popular names. On the other hand, the diseases
have been arranged according to their causes, classi-
fied according to the system generally accepted by
students in mycology.
The present work is intended as a guide to the
trucker and gardener, and to the student in Plant
Pathology. It is the result of several years of re-
search in truck crop diseases. Where information
has been drawn from other sources full references
have been given, so far as possible from the latest
investigations. The writer has aimed at making
this work as brrad and as generally useful as possible
rather than confining it to local interest.
Because of the great economic importance of the
subject of truck crop diseases, it is felt that the pres-
ent work fills a timely want and needs no apology.
We cannot expect a general text-book on Plant Path-
ology to go into lengthy treatment of all plant dis-
eases, and even less so with those of the trucking
crops. The subject in itself is too important and too
broad to be dealt with adequately in a few pages.
The time will undoubtedly come when the diseases
of every important crop will be treated separately in
Introduction Xxxi
book form. The Culture and Diseases of the Sweet
Pea, by the writer, was an attempt in that direction.
Meanwhile, until we have available the results of
more extended researches on particular crops, the
present work, it is hoped, will fill the gap.
PAR I
CHAPTER I
THE NORMAL SOIL AND ITS REQUIREMENTS
JE aim of this chapter is to study the conditions
sr which a healthy plant lives and grows. Such
wledge will prepare us to consider the causes or
ors which are responsible for abnormalities and
uses. Plants are endowed with life, and to live
must have food. Part of the food is derived
. the air, but they cannot subsist on air alone.
sustenance of plants is also derived from the
is to be regretted that laymen often regard the
as merely a conglomeration of inert particles of
lrock. If this were true, plant life would be an
yssibility. It is because soils are teeming with
ous forms of organisms beneficial to them that
t life is made possible therein. The science of
Bacteriology, though still in its infancy, has
udy taught us much to help make the trucking
ness much more profitable and successful than
as been hitherto.
ideed we may judge a soil by the kind of flora
ch predominates there, and call it fertile and
thy when this germ life helps to make it a favor-
3
4 Diseases of Truck Crops
able medium for the plants. On the contrary, we
call it sick or poor when it teems with bacteria and
fungi which act as parasites on plants, or when the
beneficial ones are absent or perform their duties
imperfectly.
STRUCTURE AND LIFE HISTORY OF BACTERIA
The term bacteria (singular bacterium), or microbe,
or germ, refers to the smallest microscopical form of
plant life. As we shall see later, bacteria are but one
of the many forms of life in the soil. The first man
to recognize bacteria was Anton van Leeuwenhoek,
a native of Holland, and a lens maker by trade. He
made use of the microscope in testing materials for
lens making. In 1675 he happened to mount in a
drop of water some tartar which he scraped off from
his teeth. To his great surprise he discovered mi-
nute little ‘‘animals’” which moved about in curious
fashions. In 1882, Robert Koch succeeded in grow-
ing bacteria artificially and outside their natural
environment. Thus was laid the foundation of the
modern science of Bacteriology.
Bacteria are very simple in form. We recognize
the rod-shaped known as Bacillus (fig. 1 a), the
spherical form as Coccus (fig. 1b), and the corkscrew
or comma form as Spirillum (fig. 1 c). Bacteria are
very minute. It would take about fifteen to twenty
thousand individual bacteria placed end to end to
make one inch in length. They occur, however, in
tremendous numbers and this enables them to per-
Gone ACERT AT
_ a. Rod shaped, b. coccus, c. spirillum, d. plate culture, showing bacterial colonies
isolated from soil.
Normal Soil and Its Requirements 5
form wonderful tasks, as we shall soon see. Bacteria
multiply in the simplest ways. A single individual
upon reaching maturity becomes constricted in the
center, then divides in two, each part now becoming
a separate individual capable of nutrition, growth,
and multiplication. It has been estimated by scien-
tists that division of a single individual takes place
about every twenty minutes. Granting that this
rate of division is uninterrupted for twenty-four
-hours, the descendants of one germ would be in round
numbers 1,800,999 trillions. These when placed
end to end would make a string two trillion miles
long, or a thread long enough to go around the earth
at the equator seventy million times. It would take
a ray of light four months, traveling as it does, to
pass from one end of it to another.
Individual bacteria can be detected only with a
compound microscope. When grown on artificial
media and under aseptic conditions, all the descend-
ants of a single parent cell live together and constitute
a colony, which becomes visible to the naked eye as
a creamy jellylike drop (fig. 1 d).
RELATIONSHIP OF BACTERIA TO THE FUNCTION OF
A SOIL
The health of a soil as shown in its fertility is in-
timately connected with the kind of bacteria present
in it. We are as yet in the dark as to the possible
function of numerous groups of the soil organisms.
Bacteriologists are seeking to discover their proper
6 Diseases of Truck Crops
functions. A recent exhaustive study' of Actinomy-
ces, or thread bacteria, in the soil seems to show that
they serve to decompose grass roots, being more
numerous in sod than in cultivated land. Oizher
groups of bacteria undoubtedly must perform other
important functions.
The mere presence of friendly bacteria in the soil,
however, would be insufficient to assure the welfare
of our cultivated lands. What concerns us most is
the work that they perform. Most of the plant’s
food as it is found in the soil is in a crude and una-
vailable form. The bits of mineral matter, the
manure or fertilizer, in the truck patches all con-
tain plant foods but in a form which plants cannot
readily use; they must be softened and predigested
and this work is done by the friendly organisms.
Plant food is therefore directly dependent on the
work of these minute scavengers. An intimate re-
lation exists between the higher and the lower forms
of plant life, the one depending on the other.
DISTRIBUTION OF SOIL BACTERIA
For a practical purpose we ought to know in what
soil and at what depth the beneficial bacteria are
most likely to abound. Since the presence of bac-
teria is necessary to maintain the fertility of a normal
healthy soil, it is essential to study the main factors
that determine their increase or decrease. We can-
not expect to find them equally distributed in differ-
*Conn, Joel H., New York (Geneva) Agr. Expt. Sta. Bul. 52:
3=1, 1916.
Normal Soil and Its Requirements 7
ent depths of the same soil. Brown* has shown that
bacteria are generally more abundant in the upper
eight inches. Table 1, adapted from Brown throws
much light on this phase of the problem.
TABLE I
Bacteria as Found in Various Depths of Soil and Under
Different Cropping Systems
Bacieria per Gram of Air-Dry Soil
Plot | Lab. | Depth of
No.2} No. |Sampling
I II Ill IV | Average
601 A 4in. |2033000]1627000]1793000]1 555000]1752000
B 8 in. |1437000]1211000]1241000]1104000]1248250
C I2in. | 541000] 567000] 559000] 525000] 546000
D 16 in. | 287000} 292000] 312000] 302000} 298250
E 201u. | 147000] 154000] 159000] 154000} 153500
F 24 in. 92300] 96500} 95100} 91500] 93850
G 30 in. 49900} 46300] 50900} 46900] 48500
H 36 in. 32900] 30000] 33100] 30400] 31600
602 A 4 in. |3102000]2870000|2917000|2947000]2959000
B 8 in. |2238000|2177000|2105000|2258000/2194500
Cc I2in. | 498000] 531000} 531000] 528000] 522000
D 16 in. | 255000] 328000] 316000} 314000] 304250
E 20 in. | 182000] 192000] F88000} 177000] 184750
F 24 in. 89200] 93300] 91600] 88300] 90600
G 30 in. 53300] 54900] 53100} 51800] 54275
H 36 in. 31700] 35700] 34200] 31300] 33225
604 A 4 in. |4606000}3908000]4210000|3932000|4164000
B 8 in. |3132000|2834000]2976000]2793000]2943750
Cc I2in. [1016000] 882000] go1000} 831000} 907500
D 16 in. | 320000] 309000] 311000] 320000] 315000
E 20 in. | 155000} 163000] 156000] 149000] 155750
F 24 in. 89400] 96100} 92900] 88900] 91825
G 30 in. 51900} 55800] 55000] 52400] 53775
H 36 in. 35100] 36600} 34900] 32600] 34800
* Brown, P. E., lowa Agr. Expt.Sta. Research Bul.8 : 283-321, 1912.
?Plot No. 601.—Continuous corn. 602.—2-year rotation, corn
and oats. 604.—3-year rotation, corn, oats, and clover.
8 Diseases of Truck Crops
In studying Table 1 we find that in every case
there is a marked decrease in soil organisms with each
increase in the depth of the soil tested. It was fur-
ther found by Brown that the moisture content was
higher for four inches than for a greater depth. It
seems evident that the decrease of soil bacteria below
twelve inches is dependent not so much on moisture
but rather on a decrease of air in the lower substratum.
It must not be expected that the data given in Table
I are applicable to every locality. Differences in
the mechanical and chemical composition of the soil
and subsoil, differences in topography, climate, and
weather conditions, will all no doubt tend to influence
more or less the increase or decrease of bacteria.
INFLUENCE OF DEPTH OF CULTIVATION ON THE
NUMBER OF SOIL BACTERIA
The work of King and Doryland* has shown that
the depth of cultivation is a potent factor in influ-
encing the number of bacteria in the soil. This is
briefly summarized by them in Table 2.
TABLE 2
Influence of Depth of Cultivation on Soil Bacteria
Silt—
plowed 4 inches deep increases the number of bacteria. .15.46%
plowed 6 inches deep increases the number of bacteria. .10.94%
plowed 8 inches deep increases the number of bacteria. .24.20%
plowed 10 inches deep increases the number of bacteria. .26.89%
* King, W. E., and Doryland, Ch., Kansas Agr. Expt. Sta. Bul.
I6I : 211-242, 1909.
Normal Soil and Its Requirements 9
Sand—
plowed 4 inches deep increases the number of bacteria. .35.06%
plowed 6 inches deep increases the number of bacteria. .13.53%
plowed 8 inches deep increases the number of bacteria. .22.90%
plowed 1oinches deep increases the number of bacteria... 5.11%
THE INFLUENCE OF MANURE ON THE NUMBER OF
SOIL BACTERIA
Besides cultivation, there are other treatments
which may lead to an increased bacterial flora in the
soil. As shown by Temple’ such a result is obtained
through the application of manure. In working with
a newly cleared sandy loam, and applying fresh cow
manure (this included solid excreta and no bedding),
at the rate of ten tons per acre, Temple obtained the
following results as shown in Table 3.
TABLE 3
Showing Number of Bacteria per Gram of Dry Soil
Soil No. 326 | Soil No. 326a
Date No Manure | With Manure
March SO TQOO: esi capone aoe as 1,220,000 1,220,000
JN asin DAS 2 1@ OVO VA Ae Mae Bh) CRN Pe ne AN 1,633,000 4,300,000
PREDIC, HOON tire Sls ih ais sche a ape heh allie 6,120,000 14,000,000
BTML TE See BOO) s: hae a ea tease Mis ck 3,780,000 10,610,000
PERRIN DUN TOOOs) pic ahs diodes SM ween 2,730,000 5,860,000
AP EULZO ATOOO Me i ei ers Davari cate 2,770,000 3,340,000
INMLBIY (G) 1G Yocom ROR Ds al NRF ea 5,510,000 5,190,000
As further evidence that manure increases the soil
flora, Temple used a clay loam, dividing it in the
following manner ; and treated as follows:
* Temple, J. C., Georgia Agr. Expt. Sta. Bul. 95 : 6-35, IgII.
10 Diseases of Truck Crops
Plat No. 1—Stable manure.
Plat No. 4—Sodium nitrate.
Plat No. 5—A complete fertilizer, PKN.
Plat No. 6—Nothing, check.
The effect of these treatments is briefly summarized
in Table 4.
TABLE 4
Colonies per Gram of Dry Soil
Date Plat No. 1| Plat No. 4| Plat No. 5 | Plat No. 6
Dee OSTOTONE. 40. 28,230,000] 11,430,000] 19,850,000 | 8,250,000
March 30, I9I1.....| 18,500,000} 9,150,000] 8,040,000} 6,240,000
May 2OntOrice . er 20,200,000] 4,850,000] 6,720,000] 5,010,000
The above Table shows that although sodium ni-
trate or a complete fertilizer increases the soil
flora, neither one can be compared to manure in
efficiency.
STRUCTURE AND LIFE HISTORY OF FUNGI
Besides bacteria of all sorts, our cultivated soils
are also teeming with fungi. The true function of
the latter remains to be studied. There seems no
doubt, however, that certain fungi like certain bac-
teria in the soil work on the organic and the mineral
matter to make it available as plant food. Parasitic
fungi depend for their food on living plants alto-
gether. Examples of these are the Uredinales, the
Fic. 2. STRUCTURE OF FUNGI.
a. Fruiting branch of Penicillium, showing
conidiophores and conidia, 6. mycelium
of Penicillium, c. an individual conidiophore
and chain of conidia of Penicillium, d. two
conidia of Penicillium, showing attachment
of spores in the chain, e. fertilization of
female oogonium by male antheridium, f.
mature oospore, g. fruiting stalks of Rhizo-
pus, h. individual fruiting head _ of Rhizo-
pus showing spores, 7. sexual fertilization
and k. zygospore of Rhizopus showing spores,
l. perithecium, showing asci and ascospores,
or winter spores, m. Pycnidium or sac in
which the summer spores are borne.
Normal Soil and Its Requirements 1:
cause of the true rust diseases. Saprophytic fungi
are those which depend for their food on the dead and
decaying organic matter in the soil. Between these
two extremes there are intermediaries. As an illus-
tration of a soil fungus may be taken the ordinary
blue mold, Penicillium expansum Lk. ‘This organ-
ism is made up of colorless feeding threads techni-
cally known as hyphe or mycelium (fig. 2b). The
spores, which correspond to the seed of higher plants,
are borne on short stalks which bear broomlike tufts
composed of chains of small bluish, round bodies, the
spores (fig. 2 a-c).
Fungi differ from the higher plants in their nu-
trition and mode of reproduction. Fungi have no
green coloring matter, chlorophyll, and are thus
unable to manufacture their own carbon by the de-
composition of carbon dioxide as do green plants.
This is why fungi must depend for their supply of
carbon on dead organic matter or on the higher plants.
Unlike the green plants, fungi have no flowers and
reproduce by means of spores (fig. 2 g-h). It has
been estimated that over 61,000 species of fungi
have been found and described on the higher plants.
The Soil Bacteriologist however has scarcely touched
on the soil fungi.
Fungi are classified according to the mode of spore
formation. In some the spores are formed by a
regular sexual union of a female egg known as oogon-
ium and of a male element, the antheridium (fig. 2 e,
i, k). The resultant fertilized spore egg is known as
oospore (fig. 2 f). Thelatter germinates by sending
12 Diseases of Truck Crops
out a germ tube, or as is more generally the case, by
the outer wall dissolving and the inner mass breaking
up into small bits of naked protoplasm known as
zoospores. Most fungi have two spore stages, the
summer form intended for rapid dissemination and
spread, the winter form intended to carry it over
through cold or any other unfavorable weather con-
ditions. The term conidia is applied to all spore
forms borne free on special fruiting stalks known
as conidiophores (fig. 2 a). A pycnidium is a sac-
like body (fig. 2 m) in which are borne the summer
spores. A perithecium is a sac-like body (fig. 2 1)
which bears the winter spores of certain fungi.
Other terms here used in describing parts of fungi
will be found in the glossary.
NATURE AND FUNCTION OF A HEALTHY SOIL FLORA
The function of a normal soil is to provide avail-
able plant food. About 95 per cent. of the com-
bustible weight of a growing plant is made up of
carbon, hydrogen, and oxygen and nitrogen. The
remaining 5 per cent. constitutes the mineral or the
ash of the plant. Carbon, hydrogen, and oxygen are
taken in the form of carbonic acid and water; nitrogen
from nitrates produced by bacteria out of organic
matter of the soil. The ash or the mineral elements
of the plant are taken directly from thesoil. Neither
the organic nor the mineral elements are in a form
which plants can make use of until they have been
acted on by certain definite organisms in the soil.
Normal Soil and Its Requirements 13
A. THE TRANSFORMATION OF CARBON
Cellulose, which is but a form of carbon, consti-
tutes a large per cent. of the woody tissue of plants.
Soils contain large amounts of cellulose and this un-
doubtedly helps to maintain their proper physical con-
dition. Straw manure, or green vegetable matter all
contain large amounts of cellulose. When it is in-
corporated in the soil, living plants cannot make use
of it, because of its complex form. It therefore must
first undergo a certain decomposition. This is ac-
complished by a group of soil bacteria known as
Amylobacter. These feed on the dead vegetable
cellulose, breaking it up and reducing it back to car-
bon dioxide, hydrogen, and fatty acids. The carbon
dioxide either returns to the air to replenish the at-
mospheric supply, or unites with water to form car-
bonic acid and soil carbonates. The carbon dioxide
is taken in by the plants either directly from the air
through the leaves, or from the soil in some carbon-
ate form. Thus we see that it is not the cellulose nor
the product of its decomposition that furnishes plant
food, but certain inorganic elements which are set free
in its decomposition.
B. ELABORATION OF AVAILABLE NITROGEN
From the viewpoint of plant nutrition, nitrogen
is unquestionably the most important of all elements.
The nitrogen of the air, although totalling about 79
per cent. of it, is not in an available form. In the
transformation of proteids into available nitrogen
14 Diseases of Truck Crops
in the soil two definite processes take place, all
thanks to the work of certain soil bacteria.
I. AMMONIFICATION. In this process, the soil
bacteria attack the complex proteids and convert
them into ammonia. The odor of ammonia from
decomposed urea, manure, or any other organic
matter is always an indication that ammonification
takes place. According to Sackett’ and others the
ability to bring about this change is attributed to the
following soil bacteria: Bacillus mycoides, Bacillus
proteus vulgaris, Bacillus mesentericus vulgatus, Bacil-
lus subtilis, Bacillus janthinus, Bactllus coli-communis,
Bacillus megatherium, Bacillus fluorescens liquefaciens,
Bacillus fluorescens putridus, and Sarcina lutea.
2. NITRIFICATION. Both ammonia and ammonia
compounds are forms of nitrogen that are not yet
readily available to plants. They must be changed
further into simpler compounds or, as the process is
known, must undergo nitrification. The ammonia
is first oxidized into nitrous acid and nitrates. This
is accomplished by two species of soil bacteria,
Nitrosomonas and Nutrosococcus. The nitrates are
then oxidized into nitric acid and nitrates, through
the work of the bacterium Nitrobacter. ‘The nitrates
are the only forms of nitrogen which plants can use.
C. ACTION OF SOIL FLORA ON MINERAL SUBSTANCES
We have already pointed out that the inert mineral
substances in the soil are not in a form in which
* Sackett, W. G., Colorado Agr. Expt, Sta. Bul. 196 : 3-39, 1916.
Normal Soil and Its Requirements 15
plants can readily assimilate them. ‘These too must
first be acted upon by certain soil bacteria.
I. CHANGES OF PHOSPHATES. Phosphates as
they commonly occur in nature are but little soluble
in water. This is why they cannot be used in their
first form, although they are required by most plants.
Soils deficient in this element may be improved by
such fertilizers as superphosphate of lime, ground
bone, phosphate rock, or Thomas slag. In the pro-
cess of decomposition that organic matter must un-
dergo as it becomes available for plant food, large
quantities of carbon dioxide are liberated which
unite with the water in the soil to form carbonic acid.
This acid attacks the insoluble phosphates, trans-
forms them into superphosphates,—the only form
soluble in water,—and renders them available to
plant life.
2. CHANGES IN POTASSIUM, SULPHUR, AND IRON.
Like phosphorus, potassium, sulphur, and iron are
made available for plants through the indirect action
of soil bacteria. The carbon dioxide and other
organic acids produced during the fermentation of
organic matter, attack the potash feldspar which
occurs in the soil. The product is potassium car-
bonate which is soluble in water and hence readily
taken up by plants. The nitric acid which is formed
during nitrification may also combine with the raw
potash in the soil forming potassium nitrate which is
a form available for plants.
As a result of the activity of soil bacteria, hydrogen
sulphide is evolved from the decomposition of pro-
16 Diseases of Truck Crops
teids. The sulphur may be further changed into
sulphur dioxide, and, when combining with water and
oxygen, into free sulphuric acid. The latter read-
ily combines with calcium or magnesium, forming
calcium or magnesium sulphate. The plant obtains
sulphur for the construction of its proteids from some
of the soluble sulphates.
How TO MAINTAIN THE FERTILITY OF SOILS
We have already seen that the fertility of a soil is
directly dependent upon the activity of certain bene-
ficial bacteria. The latter constitute the life of a soil.
It is therefore evident that for a soil to produce its
maximum, its germ flora must receive careful con-
sideration at the hands of truckers and gardeners.
We must at any cost encourage these organisms to
do their full duty at all times. Should they cease
activity the soil would become barren.
There is no doubt that plants remove large quan-
tities of plant food from the soil. Headen™ has cal-
culated that for 80,000 tons of sugar beet, there are
consumed as fertilizers, 331 tons of potash, worth
$31,100; 71 tons of phosphoric acid worth $5,680;
160 tons of nitrogen worth $54,400, making a total
of $91,180, or a trifle over one dollar per ton. What
is true for the sugar beet is true for every other
trucking crop. In other words, soil fertility is capa-
ble of being exhausted. Most of it may be returned
in the form of manure and chemical fertilizers, but
t Headen, W. P., Colorado Agr. Expt. Sta. Bul. 99: 3-16, 1905.
Normal Soil and Its Requirements 17
these are very expensive and reduce the net profit
from the crops. The object of every intelligent
trucker should therefore be to reduce his manure and
fertilizer bills by encouraging his soil bacteria to man-
ufacture the greatest amount of the available food
which his crops require. Like any other living form
these bacteria require certain conditions of life if they
are to thrive.
MAINTAINING THE NITROGEN SUPPLY
The nitrifying bacteria are air-loving organisms.
Hence the more aeration we give them, the more pro-
nounced their activity. Schlosing' determined that
when a soil was entirely void of oxygen the nitrates
were reduced, and brought about an actual evolution
of free nitrogen which is useless to the plant. With
1.5 per cent. of oxygen nitrification was marked.
When 6 per cent. oxygen was added to the soil nitri-
fication was more than doubled. It is therefore
evident that cultivation which aims at soil aeration
also accelerates nitrification. The effect of soil
aeration cannot be too strongly emphasized. Ac-
cording to Chester,? every cultivation of the soil
with its attendant aeration is equivalent to a dressing
of nitrate of sodain itscheapest form. If we realized
this, and that nitrate fertilizers are usually the most
costly, the alert trucker would learn the economy of
more cultivating.
* Schlosing, Compt. Rend. Acad. Sci. Paris, Ixxvii, 203-253.
2 Chester, F. D., Pa. State Dept. of Agr. Bul. 98: 9-88, 1912.
18 Diseases of Truck Crops
Besides oxygen, the nitrifying organisms demand,
as an indispensable condition for work, a sufficient
moisture in the soil. In dry soils and during dry
weather, nitrification is almost suspended within the
upper layers of soil. A third important factor is the
chemical reaction of the soil. The nitrifying organ-
isms work best when the soil gives a slight alkaline
reaction. Too much alkalinity, however, like too
much acidity, is detrimental as we shall see further on.
Nitrification is further dependent on soil temperature.
At 99 degrees Fahrenheit it is at its highest. A de-
gree less than 54 F. retards it considerably. At 122
degrees F. very little nitrate is produced, and at 131
degrees F. nitrification ceases entirely. The physical
condition of the soil is another important element to
be considered. The highest rate of nitrification is
found in truck lands, that is, in the sandy loams.
NITROGEN FIXATION FROM THE AIR
It has been the common knowledge of farmers and
truckers that legume plants, such as peas and beans,
cause the soil on which they are grown to become
more productive. It is not necessary here to enter
into an abstract discussion of this phenomenon.
Suffice it to say, that science has definitely shown
that there is a bacterial soil organism, Pseudomonas
radicicola, which is capable of fixing the free nitro-
gen from the air. This organism attacks the young
rootlets of the legume crops as other parasitic forms
also do. Its presence in the root results in a nodule
Normal Soil and Its Requirements 19
or swelling. Soon, however, it loses its parasitic
character and becomes an agent for fixing the free
nitrogen of the air, which is then stored up in the
root nodule. In this form the nitrogen is consumed
by the plant itself. As far as is known, P. radicicola
can thrive on the roots of legume plants only. The
Rhode Island Experiment Station’ has found that
an acre of soy beans for instance may fix about
1000 pounds of nitrogen from the air during a period
of five years, or 200 pounds per year. One hundred
and forty pounds of the 200 were removed with the
crop, and 60 pounds remained in the field. Since
one pound of nitrogen was worth at least 16c., 200
pounds would cost $32. We must not, of course,
suppose that every acre of soy beans would produce
200 pounds of nitrogen every year. This would
depend somewhat on the nature of the soil, the degree
of moisture, the amount of oxygen, and other condi-
tions congenial or unfavorable. What is certain,
however, is that every alert gardener and trucker
should learn to use legumes more extensively in his
system of cropping.
Soils which have grown leguminous crops for a
period of years are well supplied with P. radicicola.
Other soils are deficient in it and must be artificially
inoculated. The numerous types of pure cultures
of the organism sold in liquid form have as arule
proven a failure. The organism dies out or loses its
effectiveness in the artificial liquid media. The best
forms of pure cultures now used are those grown on
* Rhode Island Agr. Expt. Sta. Bul. 147.
20 Diseases of Truck Crops
sterilized soil. This method has been developed at
Cornell University. The soil is after all the natural
and best medium where soil bacteria can grow. On
it P. radicicola lives longer, and hence when it is used
for inoculation, better success may be expected.
The Alphano Humus Co. of New York City have on
the market cans with sterilized soils, in which the
legume bacteria have been introduced. Each can is
sufficient to inoculate one acre of soil. The ability of
the organism of one legume crop to inoculate another
crop has long been a subject of discussion and has not
as yet been satisfactorily answered. Garman and
Didlake* have shown that there exist six different
species of legume organisms. For example they
found that the organism of alfalfa is the same as or
similar to the one which works on the sweet clover
(Melilotus alba), trefoil or black medick (Melilotus
lupulina), and bur clover (Melilotus denticulata).
This same organism, however, cannot produce nod-
ules on the roots of any species of Trifolium, of Vicia,
Pisum, Vigna, Glycine, or Phaseolus. The organisms
of all the species of Trifolium (clover) are one and the
same. The organisms of all the species of the vetch
and garden pea are one and the same. They cannot
work, however, on red or crimson clover, or on alfalfa.
The cowpea organism seems to be adapted to the
cowpea only. ‘The same thing appears to be true for
the soy bean organism and for that of the garden
bean. Therefore when a land is to be inoculated
«Garman, H. and Didlake, Mary, Kentucky Agr. Expt. Sta. Bul.
184: 343-363, I914.
Normal Soil and Its Requirements 21
with the garden bean organism, for instance, none
must be used but those taken from the bean. Under
ordinary conditions, where a soil is known to produce
healthy crops of one (legume) variety, some of that
soil may be used to inoculate other soils intended for
the same crop.
ECONOMICAL USE OF COMMERCIAL FERTILIZER
A knowledge of the functions of soil bacteria and
a proper management of the soil means a saving of
commercial fertilizer and the proper maintenance of
soil fertility. In trucking more than in any other
phase of farming, the soil is being made to produce
the whole year around. This is especially true for
our Southern States where the summer and fall
seasons are longest, or where the winters are very
mild. It, therefore, often becomes necessary to use
chemical fertilizers to supplement the work of the
soil bacteria. This is especially true for some par-
ticular crops which draw heavily on certain mineral
constituents. In order to obtain the greatest re-
sults from the use of chemical fertilizers, the follow-
ing items should be carefully considered.
1. THE LOCATION OF THE FIELD. Uplands or
hillsides will require heavier application of fertilizer
since some of it is likely to be carried off by washing.
Lowlands, especially those near uplands which wash
badly, generally require less.
2. ‘THE CHARACTER OF THE SOIL. The chemical
composition of the soil has a marked influence on the
22 Diseases of Truck Crops
effect of fertilizers. A chemical analysis of the soil
will enable the trucker to make a more economical
use of his fertilizer. If a land, for instance, contains
too much iron and aluminium, applied phosphate
fertilizers may be modified into ferric and aluminium
phosphate, which become slowly available to plants.
On the other hand when phosphate fertilizers are
changed in the soil into tricalcium phosphate it
becomes available more readily. Sandy soils are
generally quick to respond to fertilization; they can
therefore stand heavier application than the cold clay
soils which respond more slowly. In the latter, the
fertilizers are likely to be converted into forms un-
available to plants. The trucker should therefore -
avoid depending altogether on the use of chemical
fertilizers. The best results are always obtained and
the fertility of the soil best preserved when the use of
chemical fertilizer is supplemented with animal or
green manures.
CHAPTER II
SICK SOILS NOT INFLUENCED BY PARASITES
WE have seen that a normal and healthy soil is
one in which the beneficial soil flora is at its maximum
of normal activity, making the food of the plant
assimilable. We have to discuss the abnormal or
sick soils now. In this class we include those which
are either physically or chemically so constituted as
to have a detrimental effect on the activity of the
soil flora; and those which are overrun with organ-
isms directly parasitic on the plants grown in that
soil. There are five classes to be considered inthe
first division.
I. DENITRIFIED SOILS
This detrimental condition in the soil is brought
about by a group of undesirable organisms, some
of which are Bacillus ramosus, B. pestifer, B.
mycoides, B. subtilis, B. mesentericus vulgatus.
In Chapter I we have seen that the nitrifying
bacteria oxidize the nitrogen and make it avail-
able for plants. In denitrification, the harmful
bacteria tend to reconvert the available nitrogen
into a non-available form, or else to liberate it into
the air, where it may be considered as lost so
23
24 Diseases of Truck Crops
far as the crops are concerned. Most trucking
lands contain the nitrifying and denitrifying organ-
isms in about equal proportions. To encourage
the activity of the one over the other is the aim
of intelligent trucking. The denitrifying bacteria
thrive best in an abundance of carbohydrate foods.
Fresh coarse manure with a high percentage of straw,
when applied to the soil, will favor denitrification.
It should therefore be avoided as far as is possible.
There are, however, market gardeners who often use
as much as fifty tons of such manure per acre in ad-
dition toa nitrate fertilizer. Such action is very likely
to encourage denitrification because of the large
amount of carbohydrates incorporated in the soil.
Indirectly denitrification will finally cause various
physiological plant troubles, most of which are little
understood. Poor growth and the shedding of
blossoms will characterize plants deprived of avail-
able nitrogen food. Denitrification may largely be
prevented. A judicious use of manure, especially on
the heavy soils, drainage, and proper tillage are all
factors which induce nitrification, thereby also pre-
venting denitrification.
2. NITRE-SICK SOILS
This form of sickness, peculiar to certain Colorado
soils, was carefully studied by Headen' and Sackett. 2
Nitre-sick soils are those which contain such large
quantities of nitrates that they inhibit plant growth.
* Headen, W. P., Colorado Agr. Expt. Sta. Bul. 155.
? Sackett, W. G., Colorado Agr. Expt. Sta. Bul. 196: 3-39, 1914.
Fic. 3. Nuirre-SicK BEET FIELD, SHOWING BARREN SPOTS.
Sick Soils not Influenced by Parasites 25
Truck crops (fig. 3), grains, and fruit trees rapidly
deteriorate on such lands. This condition occurs in
a variety of soils in Colorado. Itis met with in the
light sandy loams as well as in the heavy clay loams,
on lowlands as well as on hilltops. It is to be dis-
tinguished from true alkali troubles.
The distinguishing characteristic of a nitre-sick
soil is its brownish-black wet appearance. From
afar the soil looks as if it had been wetted with crude
oil; however the soil is usually dry. Sometimes the
soil may be moist and slippery, due no doubt to the
presence of large quantities of deliquescent salts.
Walking through such a field produces a sensation
similar to that which one would get from walking
on cornmeal or ashes.
The accumulation of excessive amounts of nitrates
in the soil is due to the activity of a bacterial soil
organism, Azotobacter chroococcum. ‘This organism
has the power of fixing free nitrogen from the air and
depositing it in the form of nitrates in the soil. The
conditions which favor this activity still await study.
Normally, soils contain from 140 to 150 pounds of
nitrates per acre foot. In a nitre-sick soil, each acre
foot contains 113,480 pounds, or 56.74 tons. With
such a high concentration of nitrate, it is impossible
for plants to grow. So far, we know of no methods
to reclaim nitre-sick soils.
3. ACID-SICK SOILS
Soils which contain an excess of acid in which
crops refuse to grow, may be termed acid-sick. Acids
26 Diseases of Truck Crops
in soils have a directly poisonous effect on plants.
Soil acidity may be brought about by the loss of lime
and other bases; and by the decomposition of organic
and inorganic matter.
Crops are known to draw heavily on the lime of the
soil, and thus increase the proportion of acidity.
This then is one direct way of depleting the soil lime.
A ton of alfalfa, for instance, is known to take up 50
pounds of lime. With a yield of 6 tons per acre, the
annual loss of lime per acre would be 2100 pounds.
Lime and other bases are further lost from the
soil by leaching. The soluble carbonates are but
slowly soluble in pure water. However, carbon
dioxide, nearly always present in soils, changes the
calcium carbonate into calcium bicarbonate, which
is rather soluble, and readily leaches out with the
drainage water.
Soils which are heavily manured are apt to become
more acid. The decomposition of the organic matter
yields large quantities of carbon dioxide which act on
the carbonate in the manner above indicated. The
annual leaching of lime from soils varies from 100 to
1000 pounds per acre.
In addition to these causes, poor drainage hasa
tendency to increase the soil acidity. The application
of ammonium sulphate as a fertilizer leads toa devel-
opment of acidity by the production of sulphuric acid.
The same is true when muriate of potash is added.
In the process of nitrification in which nitrogen is
made more available for plants, acids are produced.
Acidity in a soil is usually characterized by a lan-
Fic. 4. EFFECT OF LIME.
a. tod. Rhubarb, e. toh. New Zealand Spinach. a. and b., e. and f. both receiving
sulphate of ammonia, a. and e. unlimed, b. and f. limed, c. and d., g. and h. both
received nitrate of soda, c. and g. unlimed, d. and h. limed (after Hartwell and
Damon).
Sick Soils not Influenced by Parasites 27
guid condition of the growing crop. Sorrels, poverty
grass, broomsedge, cinquefoil, and redtop thrive
best, and are generally indicative of acid soils. Not
all truck crops are equally sensitive to soil acidity.
Hartwell and Damon’ have determined the degree in
which truck crops are benefited by the application of
lime to an acid soil. As a guide to the effect of lime
on crops, those which seem to benefit most are in-
dicated by the number (3), lesser degrees of improve-
ment are indicated by the numbers (2) and (1).
Crops which tolerate a moderate amount of acidity
are followed by the figure (0), and those which thrive
best without lime by (—1): Asparagus (3), beans (0),
beets (3), cabbage (2), carrots (1), cauliflower (2),
celery (3), chard (2), chicory (0), cowpea (0), cress
(0), cucumber (1), eggplant (2), endive (3), okra (3),
horseradish (2), kale (1), kohlrabi (1), leek (3), lettuce
(3), mustard (2), muskmelon (0), onion (3), parsley (0),
parsnip (3), pea, garden (1), pepper (3), potato (0),
radish (1), rape (2), rhubarb (3), sorrel (—1), spinach
(3) (fig. 4a to h), turnip (0), watermelon (—1).
Treatment of Acid Soils. The best remedy known
is lime. Its effect is to neutralize the acidity,
restoring the normal equilibrium for the activity of
the soil flora, and thus enabling the plant to flourish.
The amount of lime to be used depends largely on
the kind of soil and the degree of its acidity. Ac-
cording to Blair? a loamy to a clay loam will require
* Hartwell, B. L., and Damon, S. C., Rhode Island Agr. Expt.
Sta. Bul., 160: 408-446, I914.
2 Blair, A. W., New Jersey Agr. Expt. Sta. Cir., 54: 3-11, 1916.
28 Diseases of Truck Crops
from 1500 to 2000 pounds of burned lime per acre.
This is generally considered a moderate application.
For sands and sandy loams it would be safe to apply
1000 to 1500 pounds. If the soil is known to be very
acid or to contain large amounts of organic matter,
heavier application of lime may be given. Lime
is sold as ground limestone or as burned lime. A ton
of burned limestone will yield 1120 pounds. If
enough water is added, it will weigh 1480 pounds.
If 1120 pounds of burned lime or the 1480
pounds of hydrated lime are allowed to air slack,
the weight of both will be 2000 pounds. Aijr-slacked
lime has the same composition as ground lime-
stone. In buying hydrated lime we do not get
any better quality, but merely pay an excess in
freight for the amount of water it contains. The
cost of delivery should determine the kind of lime
to buy.
Wood ashes may often be used instead of lime to
correct soil acidity. Hardwood ashes contain about
30 per cent. lime and 60 percent. potash. Two anda
half tons of good wood ashes are equivalent to one
ton of burned lime to overcome soil acidity. Leached
ashes have lost their potash and its lime is in the form
of a hydrate or carbonate.
Magnesium lime which contains high percentages
of magnesia is not objectionable for use. In fact,
a ton of limestone which contains magnesium car-
bonate is more effective on acid soils than a ton of
limestone without magnesium carbonate. Lime
should be applied only when the acidity of the soil
Sick Soils not Influenced by Parasites 29
requires it. After that an additional application of
1000 pounds of burned lime or 2000 pounds of lime-
stone every five years will be desirable. Should lime
be used at more frequent intervals, the organic matter
of the soil will fast deplete. The saying that ‘‘lime
makes the father rich and the son poor”’ is only true
where the use of lime is overdone, and not otherwise.
4. Muck or Peat SoILs
Muck or peat soil is sick because most plants
refuse to grow there unless it is properly treated.
However, muck may be transformed into the best
trucking land. There are States in the Union
which possess muck lands by the thousands of acres.
Yet these are the last to be reclaimed. In
Europe, scientists have long concerned them-
selves with the reclaiming and utilization of muck
lands. Norway, Sweden, and Denmark have dealt
to a large extent and with fair success with the
problem, though much of it still remains to be
solved. As the term implies, peaty soils are those in
which peat is the dominating constituent. Peat is
always formed under water, in swamps or marshes,
undrained flat land, indeed, any place where water-
loving plants grow in abundance. Most peat is
made up mainly of sphagnum and moss. Grass peat
is composed of swamp grasses, sedges, rushes, or
flags. In swamps where rushes, sedges, or other
grasses occur, peat formation is more rapid than
where moss or sphagnum grows. Peat itself is
nothing more than rotten vegetable matter. Com-
30 Diseases of Truck Crops
plete decomposition is impossible, because of the
absence of air and the accumulation of plant acids
which contain antiseptic properties.
The chemical composition of peaty soils, as given
by Conner and Abbot,’ may be seen in Table 5.
TABLE 5
Chemical Analyses of Different Types of Unproductive
Black Soils.
Kind of Soil
Substance determined i
Acid Neutral
peat peat pai saat
Insoluble & soluble silica, etc. 10.40 | 9.00 88.63 |71.47
Potash (KG ©) eee eee ee 23 sue 14 .28
Dimel(Ca@) hon Wve ae Oa Eee 1.86 3.89 .08 5-91
Magnesia (MgQO)........... .26 52 att 1.31
Iron oxide (Fe,03).. bhi
Aluminum oxide (A1,03) . 2ST a Aee 7, 3.25 5.03
Phosphoric acid (P20s).. -36 -40 .08 a
Sulphur trioxide Oe -49 .28 04 | 4.42
Carbon dioxide eas .20 63 55 (00) 22
Volatile matter. . Rea 83.16 | 81.16 8.16 |12.16
otalenitrorenN sae saan ka B82 aes r 28 25/7;
Total potash (K,0).. ee 34 26 1.62 1.25
Phosphoric acid soluble’ in
INU ASIEN GE) PSOne OAS AURIS TE it .032 -0506 .0058] .037
Totallihumusss Nee ey 30.68 | 25.55 4.86 | 4.72
FMosiGh lay bliontutsyy eas unis Biel aie aia Uy TIT ANes2e 4.64 | none
Acidity in pounds calcium car-
bonate (CaCQ3) peracre foot] 1940.00 |360.00 |3500.00 | none
Hygroscopic moisture........ 11.82 | 18.57 1.65 3.30
From the table it is evident that the chemical
composition is not the same for all peaty soils. This
is naturally to be expected, since no two soils are
Conner, S. D., and Abbot, J. B., Purdue Agr. Expt. Sta. Bul.
157 : vol. 16, 1912.
Sick Soils not Influenced by Parasites 31
chemically identical. In treating peaty soils it
should be remembered that what applies to one does
not generally apply to another.
Depth of Peat Soils. WHopkins, Readhimer, and
Fisher’ classify peaty soils according to the depth
as follows:
I. Soils in which the very peaty material extends
three or four feet at least, and often to much greater
depths.
2. Soils with one to three feet of peaty material
resting on deep sand.
3. Soils with one to three feet of peaty material
resting on rock, usually with some inches of sandy
material between the two.
4. Soils with six inches to three feet of peaty
material resting on a clayey subsoil.
5. Soils with only a few inches resting on the sand.
When the peat is about three feet in depth over a
deep sand subsoil, the land may be lacking in potash.
This must then be supplied in the form of potassium
salts, or of manure.
Of the many types of peaty soils, the best for truck-
ing are those black deposits which have reached an
advanced state of decomposition, are of a fine texture,
and have a high ash content. Brown peat of a
fibrous nature is not very desirable. Its physical
condition is such that the water cannot be properly
controlled.
Treatment of Peat Soil: Burning. The mistake is
* Hopkins, C. G., Readhimer, J. E., and Fisher, O. S., Illinois Agr.
Expt. Sta. Bul. 157 : 95-131, I912.
32 Diseases of Truck Crops
often made of burning over peaty soils with a view
to improving them. This practice cannot be too
strongly condemned. It is difficult to see where any
permanent benefit can result from such treatment.
Moreover, burning destroys the nitrogen and the
organic matter, which are two valuable and expen-
sive assets of such a soil. Should peat ever catch fire
accidentally, pouring water or throwing soil on the
flames will not smother them. In this case it is best
to dig an open trench around the fire to a depth of
moist earth and let it burn itself out within that limit.
Drainage. The best method of reclaiming peat
soils is drainage. This process is not so easily done
as on ordinary land because peat holds water
better than ordinary soils. Peat soils may be
drained if sufficiently large tiles are used and a
proper outlet is at hand. The best results are ob-
tained when the tiles are laid in the underlying
muck or clay, but not too deeply in the subsoil.
Plowing. ‘The second best method of improving
peat soils is a proper working of them. Fall plowing
is to be highly recommended. The peat in this case
is exposed to the action of the frost, rain, and snow,
all of which helps in the more rapid decay of the
organic matter. In shallow peaty layers, deep
plowing is of great value. This helps to mix the
clay with the peat and makes it more readily avail-
able by bringing up the potassium and the phos-
phorus of the subsoil. In deep peaty layers, deep’
plowing exposes a larger part of the organic matter
to the air and sunlight. Rolling should never be
Sick Soils not Influenced by Parasites 33
practiced in very shallow layers. It is recommended
only where the layer is over sixteen inches deep.
Frequent cultivation is also very beneficial and pro-
vides aeration which favors a more rapid decay of
the organic matter. It helps to keep down weeds.
The Choice of a Crop. On newly reclaimed peat
soils, the best crops to plant are timothy, sudan grass,
or alsike clover, which may be pastured to advantage.
Peat soils cannot be surpassed for trucking purposes.
They seem especially adapted for onions, celery,
tomatoes, and potatoes.
Use of Fertihzers. ‘The application of certain
chemical fertilizers to peaty soils is decidedly bene-
ficial. The kind of fertilizers will depend largely on
the nature of the crop grown. Conner and Abbot
present interesting data on the effect of fertilizer on
onions. This is summarized in Table 6.
TABLE 6
Results of Field Fertilizer Tests with Onions on Various
Peat Soils
Experi-| Pounds | Average Increase in bushels per acre
ment | fertil- | unfer-
1zer tilized
No. |per acre| yteld | 4-8-10' | O-8-10 | 4-0-10 4-8-0
4-31 1000 606.9 113.0 124.2 76.3 75.5
43-I1 1000 79.1 133.1 58.0 49.6 57-1
92-21 1000 307.0 139.0 240.0 145.0 20.0
37-14 1000 234.0 332.0 285.0 120.0 89.0
t 4-8-10 formula indicates 4 per cent. nitrogen, 8 per cent. phos-
phoric acid, and to per cent. potash made from dried blood, acid phos-
phate, and sulphate of potash. Minus sign (—) indicates decrease.
3
34 Diseases of Truck Crops
TABLE 6—(Continued)
Experi-| Pounds | Average Increase in bushels per acre
ment | fertil- unfer-
1zer tilized
No. |per acre} yield 4-8-10 | 0-8-10 | 4-0-I0 | 4-8-0
eee | cme | eeeecmeeeeemeeecn | ame | ee | ce | mee
37-15 1000 613.0 Ty —27.1 2705 —64.6
43-21 1000 628.0 0.0 75.0 —30.0 25.0
SiGe 1000 394.2 89.0 49.1 55.2 47.6
57-I1a 500 372.8 D7Le7, 178.6 128.6 145.5
AV eTAS Ellery re 404.4 130.3 122.8 84.0 49.0
Cost olmerntilizens mie yaniw liars $17.34 | $9.56] $12.84 | $12.28
Average profit per acre...... 47.81 51.84 29.16 1222
We have as yet no definite data on the effect of lime
on peaty soils. Those in charge of the development
of peaty soils caution against using it too freely. Of
the forms to use, ground limestone or marl are per-
haps the best kinds to apply. The amount to use
will vary from one to four tons, depending largely on
the acidity of the soil. Too much lime tends to de-
stroy the nitrogenous compounds, and encourages
serious plant diseases.
5. ALKALI-SICK SOILS
The alkali problem is even of more widespread
concern, as it affects nearly all irrigated districts
of the arid and semi-arid regions of the United
States. An alkali-sick soil is one which contains
an excess of accumulated soluble salts which are
injurious to plant growth. For convenience,
alkali soils are divided into black and white. The
black alkali lands are known to contain sodium
carbonate or washing soda as the essential salt. The
Sick Soils not Influenced by Parasites 35
latter does not act so much on the soil as on the or-
ganic matter, turning it black. This black material
is always found on the surface with the salts. The
blackening of the soil, however, is not always an
indication of black alkali. Many dark spots are
found to contain the white alkali. Moreover, soils
which contain little or no organic matter may con-
tain large quantities of sodium carbonate and never
turn black. The white alkali in reality is not a true
alkali. The salts found in it are sodium chloride or
table salt, calcium sulphate or gypsum, sodium sul-
phate, magnesium sulphate or Epsom salt. In
addition to these may be found salts of potassium.
Table 7, taken from Harris,' shows a comparative
study of the total soluble salts which are found to be
injurious to plants.
TABLE 7
Summary of Total Soluble Salts, Chlorides, Carbonates,
and Sulphates in Alkali Soils. Average to a Depth
of Four Feet, Paris per Million of Dry Soil.
Paris of field producing best crop
Total
Counties Soluble Chlorides | Carbonates| Sulphates
Salts |
Boxelder 4,806 1,485 1,983 711
Salt Lake 2,440 545 858 2,334
Millard 10,852 640 1,418 9,795
Cache 5,792 1,573 1,515 2,539
1 Harris, F. S., Utah Agr. Expt. Sta. Bul., 145 : 3-21, 1916.
36 Diseases of Truck Crops
TABLE 7—(Continued)
Parts of field producing medium crop
Total
Counties Soluble | Chlorides | Carbonates| Sulphates
Salts
ee
Boxelder 7,075 3,021 1-727, 543
Salt Lake 4,228 875 792 1,812
Millard 18,325 3,077 1,271 13,238
Cache 17,218 2,541 888 13,126
Paris of field where no crop would grow
Boxeider 10,079 6,767 1,874 1,154
Salt Lake 6,938 2,045 689 3,636
Millard 21,488 6,289 1,875 13,304
Cache 30,148 3,585 795 23,027
Origin of Alkali Soils. Soils are formed through
the disintegration of rocks due to various agencies
such as weather, water, chemicals and organic
matter, and the action of the soil flora. In this pro-
cess, substances are released, some of which are in-
soluble while others are readily soluble in water.
Although in moist and cold climates the more
rapid decomposition of rocks leaves more salt de-
posits in the soil, the abundant rainfall washes out
these salts, which are carried off by the streams and
rivers to the ocean. This is not the case in arid
regions where the salts are gradually allowed to
accumulate. Much of the rain in the arid regions
does not find an outlet in streams, but accumulates
in the lower regions, where the water finally evapo-
Sick Soils not Influenced by Parasites 37
rates, leavinga deposit of salts. Thisthen is one way
in which alkali spots are formed. Another source of
alkali formation is through the decomposition of
volcanic rocks. This condition is found in some parts
of New Mexico. Another, and by far the most im-
portant, source of alkali formation is through capil-
larity and evaporation. This occurs when the water
accumulated in the soil is insufficient to raise the
water table high enough to permit evaporation. ‘The
condition which most favors such an accumulation
of water is a bed or layer of a clayey character which
prevents the percolation of water downwards, below
a soil which does not have sufficient lateral drainage.
The source of the water may be springs, or the perco-
lation of surface rainwater, and in irrigated regions,
leaky canals or over-irrigation. The depth of the
water table, where capillarity becomes a source of
trouble, is about threefeet. Asall soil water contains
diluted salts, continual evaporation will leave alkali
spots or beds. To realize further what the alkali
accumulation means, Tinsley* has worked out some
interesting figures.
“Suppose an acre of land, with the water table
within less than two feet of surface, and that the
amount of water evaporated from the surface in a
year was enough to cover the acre to a depth of one
foot, which the writer considers a low estimate for a
bare soil. Suppose further that when it reached the
surface, the water carried 100 parts of soluble matter
in 100,000 parts of water, which is about the salt
* Tinsley, J. D., New Mexico Agr. Expt. Sta. Bul. 42 : 3-31, 1902.
38 Diseases of Truck Crops
content of the best irrigating waters in the Roswell
district. This would give 43,560 cubic feet of water
on the acre, which would weigh about 2,720,000
pounds, and would leave on evaporation 2720 pounds
of salt, about one and one half tons.
‘This would amount to an addition of .o7 per cent.
of salt to the surface foot of that acre per year. If
this were continued about seven years, and none of
the salts were removed, the amount added would be
about .5 per cent. in the first foot of soil, which is
more per foot than cultivated plants could usually
withstand. Under actual conditions, it is probable
that more than one and one half tons of salts per acre
per year are carried to the surface in many cases, but
the rain washes a portion of them back and they are
distributed to a greater depth than one foot.”’
Effect of Alkali on Plant Growth. Plants can
stand the baneful effect of alkali only to a limited
degree. The damage is always confined to the stem
end. Here the epidermis turns brown for half an
inch or more, gradually tearing away in a girdling
fashion. This results in the collapse and death of the
plant, which assumes a corroded appearance. The
physiological effect of alkali is to plasmolize the cell
contents of the bark.
Crops Adapted to Alkali Lands. Unlike peaty
lands, alkali soils are adapted to very few trucking
crops. Sugar beets, carrots, and artichokes seem to
thrive fairly well in such soils. Irish potatoes will
thrive well in soils which do not contain more than
18,400 pounds of alkali per acre, of which 4000
piusaisiaritees st cede aiseai
ei ae an
=
EES
Sick Soils not Influenced by Parasites 39
pounds may be carbonate of soda, and 6880 pounds
common salt. Broccoli, chard, fennel, and sweet corn
will thrive fairly well in lands containing up to a total
of 3720 pounds of alkali per acre.
How to Reclaim Alkali Soils. We have seen that
the accumulation of alkali in a soil is often brought
about by the evaporation of water which is charged
with mineral salts. To obviate this it is evident
that the evaporation must be counteracted. Good
surface cultivation will establish a dry surface
mulch and prevent the rise of water to the upper
level, thereby preventing evaporation. Tillage to
be effective must be started early, because then,
large quantities of salt would be carried into the
subsoil by the spring rains. If the crop is started
early, it may be forced to maturity before the effect
of alkali can make itself felt on the plants. Tillage,
however, will afford only temporary relief, as it will
not remove the salts from the soil. Drainage on the
other hand affords permanent relief. The land is
first flooded, preferably in the winter, and then the
water which is now laden with soluble salts is removed
by a system of drainage. ‘Tile drainage, while more
expensive in its initial cost, is cheapest in the long
run. Such a system when laid down permanently
will prevent the further accumulation of salts.
The application of manure or straw to alkali land
often brings marked relief. Many a barren spot has
been reclaimed by this method. The beneficial
action of manure or straw is easily accounted for.
Both of these tend to loosen the surface soil, thereby
Ao Diseases of Truck Crops
acting as a surface mulch, and indirectly preventing
evaporation. They may also stimulate young plants
to more rapid growth, enabling them to withstand
the action of alkali. Young plants are much more
sensitive to alkali than older ones. The older plants
of cantaloupes, for instance, are far more resistant to
alkali than the young seedlings. _
CHAPTER III
SOIL SICKNESS DUE TO THE PRESENCE OF PARASITES
HARMFUL TO PLANTS
WHEN a soil is sick because its beneficial bacteria
do not perform their functions properly, or because
of abnormalities in its chemical properties, careful
treatment and proper cultural methods will restore
it to health. But when a soil becomes sick and un-
productive because parasitic forms gain a foothold
there, much greater skill and knowledge are required
to cope with the problem. Its solution is of the
greatest economic importance to the trucker and
gardener.
Parasitic fungi finding their way in a soil do not
necessarily interfere with the work of the beneficial
bacteria, such as the ammonifiers and nitrifiers, for
instance. Neither do they always influence the
chemical or physical nature of the soil. They attack
directly the crop itself. Of the numerous parasites
rendering soils unproductive, we will consider here
only two types.
I. SomL SICKNESS DUE TO PARASITIC FUNGI.
Fungi which produce DAMPING OFF in seedlings.
41
42 Diseases of Truck Crops
Fungi which produce damping off as well as WILTs,
BLIGHTS, Or ROTS in plants.
DAMPING OFF
Caused by Pythium de Baryanum Hesse.
This disease is very familiar to every grower of
plants. The trouble is peculiar to seedlings or very
tender plants. It is prevalent in the greenhouse, the
hotbed, the cold frame, and frequently also in the
field. The trouble is induced by the presence of
definite parasitic fungi in the soil. They thrive best
when the land is continually damp, and the at-
mospheric temperature comparatively high. Damp-
ing off is also favored by thick sowing and too much
shade in the seed bed.
Symptoms of Damping Off. Every experienced
trucker knows the disease when he sees it. Seedlings
freshly damped off are soft and water-soaked at the
base of the stem. If they are pulled they often break
off easily. A more careful examination shows that
the root system is entirely decayed by this time, al-
though the upper part of the stem and leaves may
still be green, possibly also fresh. The degree of
prostration in the seedlings is regulated by the
amount of moisture in the soil. If the amount of
moisture is slight, the seedlings will be flabby and
wilted before they topple over. With a high mois-
ture content, they are more firm, but become pros-
trate as soon as infection starts in. Damping off
Fic. 5. PytTaHium DEBARYANUM.
a. Mycelium, b. conidiophore bearing con-
idia, c. germinating conidium, d. fertil-
ized oogonium and adjoining empty
antheridium, e. oospore.
Soil Sickness Due to Parasites 43
usually begins in spots in the seed bed or in the field
and then may spread in every direction.
The Organism. Pythium de Baryanum was first
named and described by Hesse in 1874. Ward*
found it to be a very prevalent parasite in the garden
soils of Europe. In America the fungus was first
recognized by Atkinson? as of great economic im-
portance. Pythium de Baryanum, when examined
under a compound microscope, is seen to be made
up of coarse, non-septate, highly granular, irregular
branched hyaline vegetative threads or mycelium
(fig. 5 a). The younger threads are more finely
granular, the oldest ones are coarsely granular or
more often empty. These threads penetrate the
cells of the host, where they obtain food.
Pythium de Baryanum does not often fruit freely
on the dead host. The fruiting is better observed
when it is grown in a pure culture. Under normal
conditions the fungus produces two forms of spores,
conidia (fig. 5 b) and oogonia (fig. 5 d,e). The
summer spores, or conidia, are swellings formed at
the tip of the hyphe. These swellings readily break
off from the mother threads and germinate by send-
ing out a slender tube (fig.5 c). Thistube penetrates
the seedling tissue, where it grows and develops and
after due incubation reproduces the disease. The
oospore or sexual spore is the stage which is most
commonly found. ‘The female oogonium first devel-
* Ward, M., Quart. Jour. Micros. Soc., New Ser. 22 : 487, 1883.
2 Atkinson, G. F., New York (Cornell) Agr. Expt. Sta. Bul. 94 :
233-272, 1895.
44 Diseases of Truck Crops
ops as a terminal enlargement which is cut off by a
septum from the mother thread. Next or adjacent
to it a slender tube is cut off from the mycelium by a
septum. This tube now performs the function of the
male sexual organ and is known as antheridium.
The latter then comes into close contact and empties
all its content into the oogonium (fig.5 d). Fertiliza-
tion thus takes place, and a mature egg or oospore
or winter resting spore is formed (fig. 5 e).
The latest investigations have not yet disclosed
whether or not Pythium de Baryanum is carried over
from year to year by its oospores. It is apparently
able to propagate itself indefinitely by its vegetative
mycelium. The seedlings of the following truck crops
are subject to damping off by Pythium: Beans, beets,
cabbage, cauliflower, endive, lettuce, pumpkin, tom-
ato, and turnip.
Of the other fungi which are capable of producing a
damping off in seedlings may be mentioned; Sclero-
linia libertzana Fckl., Phoma solani Halst., Colle-
totrichum sp., Fusarium sp., Sclerottum Rolfsi Sacc.,
and Rhizoctonia solani Kihn. ‘The first five will be
taken up separately in connection with the study of
their respective hosts (see pages 45, 46, 143, 305, 324).
OTHER SOIL DISEASES
We have seen that Pythium de Baryanum is most
active as a disease on young seedlings. Other fungi,
however, may attack not only seedlings, but also
older plants, in various stages of development. As
ne
Fic. 6. RHIZOCTONIA.
a. Rhizoctonia cankers on stems of young bean plants, b. young growing hyphe
of Rhizoctonia, c. young barrel shaped cells which compose the sclerotia of Rhizoc-
tonia, d. older and empty barrel shaped cells of sclerotia (a. to d. after Peltier).
Soil Sickness Due to Parasites 45
a guide to the trucker and gardener, we shall consider
two typical soil diseases, one which produces root
rot, the other wilt only.
Root Rot
Caused by Rhizoctonia solani Kahn.
This fungus is of great economic importance be-
cause of its widespread distribution. It is capable
of producing a damping off on a variety of seedlings,
as well as of attacking older and mature plants.
Symptoms. The symptoms of Rhizoctonia wilt
do not differ materially from those produced by
Pythium de Baryanum. On older plants however
Rhizoctonia produces cankers or deep lesions which
are very characteristic (fig. 6 a). These are formed
on the roots as well as on the base of the stem.
The lesions are reddish brown and extend into the
cortical or vital layer as well as into the woody tissue.
There is perhaps no other parasitic fungus which is
so widespread and capable of attacking such a vari-
ety of hosts as Rhizoctonia. The work of Peltier*
shows that the following truck crops are susceptible
to Rhizoctonia: Beet, bean, cabbage, cauliflower,
celery, cowpea, cucumber, cress, eggplant, horse-
radish, lettuce, muskmelon, okra, pepper, radish,
squash, sweet potato, garden pea, parsnip, potato,
and tomato.
The Organism. In 1828 Duhamel described Rhi-
t Peltier, G. L., Illinois Agr. Expt. Sta. Bul. 189: 283-391, 1916.
46 Diseases of Truck Crops
zoctonia for the first time. In the United States the
first extended account of the fungus was given by
Pammel.* Many other excellent accounts by Amer-
ican workers have appeared from time to time, to
which we shall have occasion to refer later.
The genus Rhizoctonia includes several forms of
sterile fungi, all of which are distinguished by their
manner of growth in pure culture, and by their
mycelium form. Young hyphe of R. solani Ktthn
are at first hyaline, then deepen in color from a yellow-
ish to a deep brown. The young branches are some-
what narrowed at their point of union with the parent
hypha and grow ina direction almost parallel to each
other (fig. 6 b). A septum is also laid down ata
short distance from the point of union with the par-
ent mycelium. There is another form of mycelium
which is made up of barrel-shaped cells, each of which
is capable of germinating like a spore (fig.6 c,d). In
pure cultures R. solani produces sclerotia, which are at
first soft, whitish, and later become hard and dark.
The fungus is carried over from year to year as scler-
otia which are able to withstand the effect of heat,
cold, drought, or moisture.
PARASITIC SOIL FUSARIA
Next in importance to Rhizoctonia is a group of
fungi which belong to the genus Fusarium. Lands
infected with these species of fungi become unfit for
cabbage, potatoes, tomatoes, etc., causing great finan-
*Pammel, L. H., Iowa Agr. Expt. Sta. Bul. 15: 244-251, 1891.
¢ ae gene’ Bis ut : : ae 2 op Ta ea
| a a mM She 2 ‘ i. % SS ae
Fic. 7. Fusarium WILT.
a. Early stage of Fusarium wilt of sweet potato, b. sweet potato hill killed
by Fusarium wilt, c. spores of Fusarium batatatis, d. spores of Fusarium hyper-
oxysporum, e. chlamydospores of Fusarium (c. and d. after Harter).
Soil Sickness Due to Parasites A7
cial losses to the trucker. We will take up the specific
troubles in studying each of these crops respectively.
As an illustration of a typical Fusarium-sick soil we
will consider the wilt of sweet potatoes.
WILT OR YELLOWS OF THE SWEET POTATO
Caused by Fusarium batatatis Woll. and F. hyper-
oxysporum Woll.
Symptoms. The first indication of sweet potato
wilt is a slight difference in the color of the foliage
in the affected plants. The leaves become dull, then
yellow between the veins and slightly puckered; this
is followed by the wilting of the affected vines (fig.
7a). If one of these vines be split open at the stem
end, the interior of the woody portion will be found
blackened. All parasitic soil Fusaria invade the
interior of the water or fibro-vascular bundles which
are situated in the woody tissue of the stem. Wilting
and death of the plant follow (fig. 7 b).
The morphology of Fusarium is identical in many
species. They differ only from a pathological point
of view, and in peculiarity of certain colors produced
on media in pure cultures. Pathologically, many of
the species are distinct. The Fusarium of the sweet
potato wilt cannot, as far as we know, attack potatoes,
tomatoes, or any other host. This is similarly true
for the Fusarium which produces a wilt on tomatoes,
etc. The mycelium of Fusarium is hyaline, septate,
and branched. The spores are sickle-shaped and
48 Diseases of Truck Crops
very characteristic (fig. 7 c, d). Some Fusaria also
produce chlamydospores or resting spores, by which
the fungus is carried over winter (fig.7e). As faras
we know the wilt-producing Fusaria do not form a
winter or ascus stage. They are carried over as
mycelium, or chlamydospores, in dead plants and in
the soil.
2. SOILS RENDERED SICK BY CERTAIN FORMS
OF ANIMAL LIFE
The present discussion deals with the root knot, a
disease produced by a little worm generally known as
nematode, or eel worm.
ROOT KNOT
Caused by Heterodera radicicola (Greef) Mill.
Root knot is most prevalent in light soils. This,
however, does not exclude it from heavier lands where
it may sometimes be found. The trouble is most
widespread in the Southern States, where the winter
is mild. In unprotected places in the North its
numbers are probably greatly reduced each winter.
The annual financial losses from this disease are
staggering in extent. With proper culture and fer-
tilization, however, a crop may be produced with
practically very little loss where neglect would have
caused a total failure. This is especially true under
greenhouse conditions.
Fic. 8. NEMATODE Root Knot.
a. Root knot of Irish potato, b. root knot of onion, c. root knot of parsnip, d.
egg of nematode, Heterodera radicicola, e. young female worm, f. half-grown female
worm, g. young male worm, hk. matured male worm ready to emerge from old body
covering, ¢. matured female worm (d. to 7. greatly enlarged, after Stone and Smith).
Soil Sickness Due to Parasites 49
Symptoms. The disease is characterized by a
swelling on the roots, showing itself in small knots
formed either singly or in pairs, or in strings, giving
the affected root a beaded appearance (fig. 8 a, b).
Sometimes, however, the swellings are so large that
they may be mistaken for the root nodules (fig. 8 c)
of legume plants, which occur normally in great
abundance. Infested plants usually linger for a long
time, but they can be distinguished by a thin growth
and yellow sickly looking leaves and stems.
Distribution. The eelworm seems to be of world-
wide distribution, being found in Europe, Asia,
Australia, and both North and South America.
And yet, there are many localities in which this pest
has never been known.
Life History. The eelworm is a very minute worm,
seldom exceeding one twenty-fifth of an inch in
length. It is semitransparent, so that it cannot be
easily detected by the nakedeye. In searching for the
eelworm, break afresh knot. Close examination will
reveal two types of worms: a spindle-shaped worm,
the male (fig. 8 g, h), and a pearly white pear-shaped
organism, the female (fig. 8 e, f), firmly embedded in
the gall tissue. The female is very prolific, depositing
no less than 400 to 500 eggs during her lifetime.
The eggs are whitish (fig. 8 d), semitransparent
bean-shaped bodies, and too small to be noticed
without the aid of a magnifying glass. The time
which elapses until the eggs hatch depends largely
upon weather conditions. In warm days the eggs
hatch sooner than in cold days. Upon hatching, the.
4
50 Diseases of Truck Crops
young larve either remain in the tissue of the host
plant in which they have emerged, or, as is more often
the case, leave the host and enter the soil. This is
the only period during which the worms move about
to any great extent in the soil, where they either
remain for some length of time or immediately pene-
trate another root of the host. The nematodes in
most cases become completely buried in the root
tissue, establishing themselves in the soft cellular
structure which is rich in food. The head of the
worm is provided with a boring apparatus consisting
of a sharply pointed spear, located in the mouth.
This structure not only aids it in getting food but is
also valuable in helping the young worms to batter
through the cell walls before becoming definitely
located. The two sexes during the development. are
undistinguishable up to fifteen or twenty days, both
being spindle-shaped. In the molting or shedding
of the skin, there is a marked change in the case of
the female, especially in the posterior region of the
body, which no longer possesses a tail-like appendage.
Fertilization occurs soon after this molt, and many
radical changes occur in the shape and structure of
the organization of the worm. The fertilized female
increases rapidly in breadth and becomes a pearly
white flask- or pear-shaped individual (fig. 8 i).
At this stage it is far from being wormlike and may,
therefore, be overlooked by one unfamiliar with the
life-history of the eelworm. The adult male is much
like that of the young female larve, being spindle-
shaped in outline. The male does not cause as much
Soil Sickness Due to Parasites Ga
damage to the root tissue as the female, and its pur-
pose in life seems to be only that of fertilizing the
female, for after this function has been performed,
it is quite probable that the male worm takes no
more food.
Omnivorous Nature of the Eelworm. ‘There are
almost five hundred species of plants known to
suffer from the eelworm. This number includes
all the important families of the flowering plants.
According to Bessey? the following are among the
plants subject to root knot:
a. Truck Crops. Asparagus, bean, beet, cabbage,
carrot, cauliflower, celery, chicory, cucumber, dill,
egeplant, endive, gourd, Jerusalem artichoke, leek, let-
tuce, muskmelon, mustard, okra, onion, parsley, pars-
nip, pea, pepper, potato, pumpkin, radish, rutabaga,
salsify, shallot, spanish oyster plant, spinach, squash,
sweet potato, tomato, turnip, watermelon, yam.
b. Garden Weeds. Birdsfoot trefoil, burdock, car-
petweed, dandelion, dead nettle, Florida beggarweed,
horse nettle, lamb’s-quarters, mayweed, milkweed,
nightshade, pigweed, plantain, pokeweed, ribgrass,
shepherd’s-purse, sheep sorrel, snow thistle, wild
morning-glory.
From the above large list of susceptible hosts, it
is evident that the trucker cannot afford to permit
infestation of his land. Once a soil becomes sick
because of the presence of eelworm there is very
little range left in the choice of a crop.
1 Bessey, E. A., U. S. Dept. Agr. Bureau Pl. Ind. Bul. 217:
7-89, I9II. |
52 Diseases of Truck Crops
SOIL-INFESTING INSECTS
Soils infested with insect pests are as sick as when
infested with eelworm or parasitic fungi. The
trucker, in sowing his seed, has often great difficulty
in obtaining a good and even stand. The frequent
resowings invariably result in late crops, and this
means heavy money losses. Frequently the stand
is reduced by fifty per cent. in spite of the many
resowings. The cause of this may be traced to the
presence in the soil of certain insect pests. Among
those dreaded most by the trucker and gardener are:
Cutworms (A grotis sp.), (Lycophotia sp.), (Peridroma
sp.), wireworms (Melanotus sp.), and white grubs
(Phyllophaga sp.).
CHAPTER IV
METHODS OF TREATING SICK SOILS
~ DAMPING OFF, whether induced by Pythium, Rhi-
zoctonia, or any ether parasitic organism, is usually
confined to seedlings in the seed bed, under cover or
in the open. The loss of seedlings not only means a
waste of seeds, but it also results in late crops.
Growers are usually in the habit of using the same
soil in the seed bed, year in and year out. This prac-
tice cannot be encouraged, since contamination of
the seed-bed soil is bound to take place. The dis-
ease-producing organisms are usually brought in
with the manure. A number of truckers make it a
practice to empty their beds and fill them with fresh
soil. This, unfortunately, is not always a safe
method, for the reason that the new soil too may
be contaminated, or that it may become infected
as soon as it is placed in the bed previously con-
taminated. Sick seed-bed soils may be freed from
damping off in various ways.
Formaldehyde. When steam sterilization is not
feasible because of the absence of a steam boiler, the
formaldehyde treatment is the next best. With this
treatment we may control Fusarium, Rhizoctonia,
33
54 Diseases of Truck Crops
and Pythium in infected beds. It is doubtful,
however, if this treatment will entirely eradicate eel-
worms from infested soils. ‘The method is as fol-
lows: the beds are thoroughly prepared in the usual
way, and then drenched with a gallon per square
foot of formaldehyde solution composed of one pint
of commercial formaldehyde (40% pure) to thirty
gallons of water. The solution should be put on with
a watering can and distributed as evenly as possible
over the bed, so as to wet the soil thoroughly to a
depth of a foot. It will, in most cases, be necessary
to apply the solution two or three times, as the soil
may not absorb the full quantity of the liquid at one
time. After the treatment the beds should be cov-
ered with a heavy burlap to keep in the formaldehyde
fumes for a day or two, and then aired for a week
before planting. Stirring the soil at once would help |
the escape of the fumes. Formaldehyde may be
bought in any drug store 40% pure.
Steaming. This method of treatment is far supe-
rior to any other yet evolved. For seed beds on a
large scale the inverted pan method is the best. This
was first devised by A. D. Shamel of the U. 8S. De-
partment of Agriculture. The boiler must be able to
generate a pressure of not less than eighty pounds,
which should be maintained for at least one and a
half hours. In setting a pan the rim is sunk into the
soil of the seed bed, to a depth of two to three inches,
to make the inclosed chamber steam tight. In
heavy soil, trenching may be necessary. It is also
advisable to put a heavy weight on the pan when the
(AFTER SELBY.)
Fic. 10. SURFACE WATERING. SHOWING PORTABLE SPRAY EQUIPMENT
UsED IN GARDENS ABOUT COLD FRAMES AND Hort BEeEps.
(AFTER WILLIAMS.)
Methods of Treating Sick Soils 55
steam operates. When one pan is used, a traction
engine or a portable boiler of ten to twelve H. P.
will suffice. While the standard size of the pan is
six by eight feet, the dimensions may be modified
to suit the size of the seed beds.
Selby and Humbert* describe the method of con-
structing an inverted (fig. 9) pan as follows:
‘Material used for construction of a pan is gal-
vanized sheet iron; the most useful weight is No. 20
gauge, which weighs 26.5 ounces per square foot.
The heavier material requires little in the way of
frame supports. The galvanized iron sheets come in
sizes varying from two to three feet in width by eight
to ten feet in length. Figure 9 shows a pan 6 x 10
feet in size, 6 inches deep, constructed from five such
strips 214 x 8 feet in size. These sheets are joined by
double-fold seam and riveted at intervals of 6 to Io
inches to make the pan steam tight. This pan is
further strengthened by a band of strap iron2x I inch
riveted to the bottom edge, and stiffened by a brace
of 114 inch angle iron across the top and extending
down the sides. This is bolted at the sides to the
supporting strap iron stiffener. The corner illustra-
tions show at ‘A’ the joint used for the galvanized
iron sheets, and ‘B’ a section of the angle iron sup-
porting the top.
‘“The entrance pipe for the steam may be placed
at the side or end of the pan (see dotted construction
lines of fig. 9) or may enter from the top as per illus-
t Selby, A. D., and Humbert, J. G., Ohio Agr. Expt. Sta. Circ. 151 :
65-74, 1915.
56 Diseases of Truck Crops
tration. The latter form has the advantage in
that it will not interfere with the box boards when
used on frames. The pipe, after entrance, should
be a T form, so that steam in being forced into
the pan when in place does not blow holes in the
soil.”’
Surface Firing. ‘This method of soil sterilization is
used only in the absence of steam facilities or where
formaldehyde cannot be obtained, which, however,
is seldom the case. It consists simply in producing
a hot fire for an hour or more over the bed to be ster-
ilized. A combustible material such as brush, straw,
or wood may be used for that purpose. The objec-
tion to it is that the fire may destroy the organic
matter in the soil.
Roasting or Pan Firing. In this method the soil
to be sterilized is removed from the bed and placed
in a pan, underneath which fire is present. After
roasting the soil is returned to the bed and more
of it sterilized. This method is too slow and is
open to the same objection as the surface burning.
The advantage of steam sterilization and of the
‘fire’? methods consists in the destruction of all
weed seed, together with the fungi which cause
damping off.
Other Methods of Control. Damping off may be
largely controlled by careful cultural conditions.
Unless the soil of the seed bed is to be sterilized, it
is never wise to sow the seeds in beds where damping
off was known to have occurred previously. Thick
sowing especially should not be permitted. In
Methods of Treating Sick Soils 57
Table 8, Johnson* presents some interesting data on
the effect of thick sowing on damping off.
TABLE 8
Effect of Thick Sowing on Percentage of Diseased Plants.
Weight of seed sown
Flat No. Tin aca || Lents. Drscased
per flat | per 100 sq. ft.
Grams Ounces Per cent.
Mere apens eid Shei ater Steve 0.1 0.16 fo)
7} aie eats eae 0.2 0.33 fo)
Gis AN ee acco eee Bee US 0.3 0.49 8
Bie Merson ctiate saci teens 0.4 0.66 15
Shoiahd RE pec itaar eee: 0.5 0.83 35
(Cah A eg RA Ee 0.6 0.99 75
re es re Sh at 0.7 1.16 80
te a La aan Ler oy ieee te 0.8 133 80
Os Chas Cie eae lee Net 0.9 1.49 92
WORE ask c hace anata 1.0 1.60 96
Certain soils are especially favorable to damping
off. Soils which contain a high percentage of un-
rotted vegetable matter and those which are hard to
drain need especial attention. Great care should be
taken that the seed bed is kept at the right tempera-
ture. The latter cannot be guessed at by personal
sensation. It should be accurately determined by
thermometers placed in the bed at suitable distances.
It should also be remembered that any covering cloth
or sash will exclude light and air. Every precaution
* Johnson, James, Wisconsin Agr. Expt. Sta. Research Bul. 31:
31-61, 1914.
58 Diseases of Truck Crops
should be taken to prevent the seedlings from be-
coming ‘‘drawn,”’ for at that stage they are most
susceptible to damping off. The safest plan is to
keep the temperature a trifle lower than is gener-
ally required, and allow as much ventilation as
possible. Very often damping off starts in one
corner of the bed. To check the rapid spread of the
disease, the infected area may be removed. Spray-
ing the seedlings with various fungicides in a bed
where damping off has become well established will
be of little help.
CONTROL OF FUSARIUM- AND NEMATODE-SICK SOILS
The formaldehyde or the steam sterilization meth-
ods which are so effective in the treatment of sick
seed beds cannot be used on a large scale for sick
soils on account of the extensive cost involved. The
trucker, therefore, must resort to other methods of
control. Soils which are made sick by the presence
of parasitic fungi or nematodes may be reclaimed by
crop rotation as well as by the development of wilt-
resistant varieties. Both of these methods will be
discussed at length in pages 372, 373.
CONTROL OF INSECT-INFESTED SOIL
Spraying the soil will be of little value in the control
of underground insect pests. Fortunately, however,
we have more effective means for dealing with them.
To destroy wireworms, sow corn which has been
Methods of Treating Sick Soils 59
soaked for ten days in water containing arsenic
or strychnine sulphate before planting the regular
crop. The larve will feed on the poisonous corn
kernels and die. Another way is to treat the seed
with gas (coal) tar.
White grubs may be controlled by the use of bisul-
phide of carbon. Fall plowing is a valuable remedy,
since many of the grubs are thus exposed to the cold
winter weather and killed.
Cutworms may be controlled by the use of a
poisoned bran made as follows: to three ounces of
molasses add one gallon of water and sufficient bran
to make a fairly stiffened mixture. To thisadd Paris
green or arsenic and stir well into a paste. A heap-
ing teaspoonful of the mixture is scattered here and
there over the infested land.
PARTY if
61
CHAPTER V
THE HEALTHY HOST AND ITS REQUIREMENTS
WE have seen that soil is the medium in which
plant life is made possible. We have also seen
that to produce good yields in crops it is essen-
tial to have a healthy soil—a condition directly
dependent upon the work of friendly organisms.
When these perform their work imperfectly, or
when the soil is overrun by parasitic fungi or
by pestiferous animal life, the soil is considered
sick.
Let us now consider the plant itself, since
practically and economically it is the crop
that concerns us most. We are interested in
the soil only in so far as it is capable of main-
‘taining economic crops. The general needs of
plant life are the same to a striking extent for
higher plants and for the lower microérganisms
of the soil.
NEED oF AIR
Plants must breathe, since air is indispensable
63
64 Diseases of Truck Crops
for all life. Plants breathe through their leaves,
and, according to Whitney,* through the roots also.
Hence, cultivation is necessary not only to supply
air to the microérganisms in the soil, but also to
the roots of the crop. In the opinion of Whitney,
cultivation accomplishes a step further; by
stirring the soil we permit the escape of foul gases
given off by the plant roots as well as by the soil
organisms.
NEED OF WATER
Plants to live’ must ‘drink.’, This is *one” or
the most important considerations from the
trucker’s point of view. It is generally sup-
posed that roots are fixed things in the soil,
receiving water and food material by capillary
action. This occurs only in very moist and
saturated soils. However, in dry seasons and
in dry soils the roots have to move down-
ward towards the water. This may be proved
by a simple ingenious experiment described by
Whitney." li “you” take: some > ‘soi!’ fromthe
field with what we call an optimum amount of
moisture, or the best amount for plant growth,
put it in a tumbler, filling the tumbler about
half full, and put some dry soil on the surface,
tWhitney, Milton, U. S. Depart. of Agr. Farmers Bul. 257:
5735, 1909.
Healthy Host and Its Requirements 65
you can see the difference in moisture contents
by the difference in color, the moist soil being
Gatker than) the dry.) Then, -if “you, cover’ the
tumbler to prevent evaporation you can leave
the dry soil in contact with the moist soil and
there will be no appreciable interchange of mois-
ture between the moist and the dry layers. This
simple experiment demonstrates that if cultiva-
tion is also to conserve the soil moisture, we
must always strive to form a pulverized dry
mulch on top. Capillary action practically ceases
when a dry mulch or layer is found on top of the
soil.”’
From the trucker’s point of view, the water re-
quirement of crops deserves careful consideration.
In intensive gardening the water supplied by natura
precipitation of rainfall cannot always be depended
upon for crop production, and must be supplemented
by irrigation. In fact irrigation is often a funda-
mental requirement, if we are to meet ina timely way
the demands of the market. Irrigation when prop-
erly carried out may mean success, and the opposite
total failure. To be what farmers call a ‘‘water
hog,’’ using too much water, is detrimental to the
crops, for they are very sensitive to an excess of it.
Widtsoe and Merrill* have shown that the yields of
truck crops directly depend on the proper amount of
water supplied. The result of their investigation is
shown in Table 9.
t Widtsoe, J. A., and Merrill, L. A., Utah Agr. Expt. Sta. Bul. 117:
69-119, I912.
si
66 Diseases of Truck Crops
TABLE 9
The Yields of Truck Crops as Harvested, with Different
Quantities of Water
Yield of crops is expressed in Ibs. per acre; quantities of water used
are expressed in acre-inches.*
CARROTS
1. Irrigation water supplied] 3.75} 7-50} 15.00] 25.00] 35.00} 60.00
2. Rainfall and soil water..} 10.25] 10.25] 10.25] 10.25] 10.25} 10.25
3. Total water for use of
pe 616 ) aed MOM SOE RN SR 14.00] 17.75] 25.25] 35-25] 45.25] 70.25
4. Total. yield of carrots
(Ibs. per acre)....... 34577| 33223] 49507| 46755] 56930} 68420
5. Yield per inch of irriga-
HOM WALETy 2.00 sae 9221] 4430] 3306] 1871} 1627] 1129
6. Yield per inch of total
WELUED evista d siantorer ets 2469| 1872| 1963} 1326] 1258) 974
CABBAGE
1. Irrigation water supplied......} 12.50] 20.00] 25.00} 40.00] 70.00
2. Rainfall and soil water........] 5-54) 5-54] 5-54) 5-541 5-54
3. Total water for use of crop... .| 18.04] 25.54] 30.54! 45-54] 75-54
4. Total yield of cabbage (Ibs. per
ACES) Ay sy a SNORE ay Netcare? 18490] 18524] 16310] 20432] 23098
s. Yield per inch of irrigation
WEL LETV Nira: se ueucitueholent ean ee LAZO! O26] O52 SuLbnessO
6. Yield per inch of total water...} 1025} 725] 534] 449] 306
ONIONS
1. Irrigation water supplied............] 15.00] 20.00] 30.00] 65.00
piikamialvandsoily waternenitee acer 5.54, 5-54] 5-541 5-54
3. Total water for use of crop.........- 20.54| 25.54] 35-54] 70.54
4. Total yield of onions (lbs. per acre)...| 21471] 22038] 32437] 34171
5. Yield per inch of irrigation water.....] 1432] 1102] 1098} 526
6. Yield per inch of total water.........} 1045} 863] 913) 484
t The term acre-inch means the quantity that will cover one acre to
the depth of oneinch. Likewise in speaking of an acre-foot of water,
it means the water necessary to cover one acre toa depth of one foot.
Healthy Host and Its Requirements 67
A careful study of Table 9 shows that excessive
watering results in a decrease of yield. Widtsoe and
Merrill in their work on sugar beets found that when
30 acre-inches of water is spread over one acre 30
inches deep, the yield was 20.82 tons. When this
same amount of water was spread over two acres
and for a depth of fifteen inches, the yield increased
to 38.90 tons per acre. Finally when the 30 acre-
inches of water were spread over six acres and five
inches deep, the yield increased to 82.68 tons per
acre. Every trucker should study the water require-
ments of the crops under his conditions of soil and
climate. To obtain the best results from irrigation
we must be familiar with the root system of each
particular crop and the depth to which it normally
penetrates the ground.
Methods of Irrigation. There are two methods of
watering recommended. Each trucker can determine
for himself which of the two will give him the best
results under his particular conditions.
(a) Subtrrigation. As this implies, the water is
applied underground and through perforated pipes.
The conditions necessary for subirrigation are a clay
subsoil or a hardpan capable of retaining the irriga-
tion water. The topsoil must be of a sandy loam,
neither too loose nor too compact. The land must
be of a nature to admit of perfect drainage, having
a fall of one inch to each one hundred feet. The land
must also be level without raised places. Where
these conditions cannot be fulfilled, subirrigation
will prove a failure. The crops that are best bene-
68 Diseases of Truck Crops
fited by subirrigation are celery, lettuce, and Irish
potatoes. ‘Tomatoes, watermelons, cantaloupes, or
sweet potatoes are not benefited by it.
The advantages claimed for subirrigation are many:
(1) The moisture is better controlled in the soil and
the roots will have easy access to it. (2) No crust
is formed to shut out the air from the soil, or to fa-
vor the development of fungous diseases. (3) The
soluble salts and fertilizers are not washed down
deeply and are not carried beyond the reach of the
roots.
(6) Surface or Spray Irrigation. As this implies,
water is applied on the surface overhead, in the form
of rain (fig. 10). The many advantages claimed for
this system are as follows: (1) For the same volume of
water a much larger area may be irrigated, or the
same area may be watered with a smaller quantity of
water. (2) Very little skilled labor is necessary in
this system. (3) Large areas for irrigation can be
rapidly covered. (4) The rain effect will control
frosts. (5) There are no leaky wasteful channels, and
no boggy roads. (6) An economy of land in channels
and ditches. (7) Spray irrigation is independent
of the topography of the field, and may be extended
to lands too rolling or rough for subirrigation.
Truckers in the arid sections seem in favor of a com-
bination of spray and surface irrigation on the same
field. The spray is used in preparing the seed bed,
germinating the seeds, and for newly set out plants.
Later, as the crop advances in age, especially during
blossoming and fruiting, irrigation is carried out by
Healthy Host and Its Requirements 60
surface furrow or check methods.
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190 Diseases of Truck Crops
should be taken to exclude club roots from the seed
bed, since many an outbreak of this trouble may be
traced back to the use of previously infected seedlings.
BLAcK Rot
Caused by Pseudomonas campestris (Pammel)
Ew. Sm.
The disease is known to growers as stem rot and
black rot. The latter perhaps is the more common
name. The trouble may now be found wherever
cabbage is grown on a large scale.
Symptoms. Black rot has distinct symptoms
which cannot easily be confused with other cabbage
diseases. On the leaves, the symptoms are mani-
fested as a burning appearance on the edges (fig.
30 d) and a yellowing of all the affected parts except
the veins, which remain blackened. From the mar-
gin of the leaves the disease works downwards to the
stalk. From there the disease travels up again to
the leaves and from there to the stems. The parasite
works in the fibro-vascular bundles of the leaves and
main stalk, causing a premature defoliation. Occa-
sionally, the disease enters one side of the stalk, the
latter becoming dwarfed and the cabbage head be-
coming one sided. In severe cases of attack, there is
a total lack of head formation. In splitting open a
stump of an affected plant, we will find a black ring
which would correspond to the places of the fibro-
vascular bundles invaded by the organism. Smith*
t Smith, E. F., U.S. Dept. of Agr. Farmers Bul., 68: 5-21, 1898.
Family Cruciferze 191
found that the infection takes place through small
openings naturally found on the leaves and known as
water pores which are found scattered over the teeth
of the leaves. Infection by means of insect bites is
also a very common occurrence. Outbreaks of black
rot in new fields may undoubtedly be traced back
to the use of infected manure. Black rot also at-
tacks broccoli, Brussels sprouts, cauliflower, char-
lock, collard, kale, kohlrabi, black mustard, rape,
rutabaga, radish, sweede, and turnip.
The Organism. Pseudomonas campestris is a rod-
shaped organism, slightly longer than it is broad.
When young it is actively motile by means of long
polar flagella (fig.30e). Itis found single or in pairs
and produces no spores. It liquefies gelatine com-
pletely in about fifteen days. On agar plates the col-
onies are round, yellow in color, and the margin entire.
On potatoes a copious growth is produced with
no odor and no browning of substances. The in-
vestigations of Harding’ and others have proved
that the black rot germ may be introduced into the
seed bed and into new fields from infected cabbage
patches. The virulence of black rot is largely de-
pendent on the weather. It is unfortunate that
favorable weather conditions for the cabbage plants
are also favorable for the disease.
Control. Before planting, cabbage seed should be
disinfected for fifteen minutes in a solution of 14 pint
of pure (40%) formaldehyde diluted in seven gallons
t Harding, H. A., New York (Geneva) Agr. Expt. Sta. Bul.,
251: 178-194, 1904.
192 Diseases of Truck Crops
of water. Inmaking the seed bed, manure known to
be free from cabbage refuse should beused. Allinsect
pests should be kept in check by spraying, and no
animals should be allowed to roam in sick patches.
Insects and farm animals act as carriers of black
rot. The disease cannot be controlled by merely
cutting off diseased foliage. If anything, this
operation aggravates the trouble. Diseased plants
should be pulled out and destroyed. Crop rotation
should be practiced wherever the disease is well
established.
SOFT Rot
Caused by Bacillus carotovorus Jones.
Soft rot, although a field trouble, causes great
damage to stored cabbage. The greatest losses
are reported from New York and Wisconsin where
cabbage is stored on a large scale.
Symptoms. ‘The disease is characterized by a soft,
mushy to slimy decay of the entire plant. The dis-
ease works very rapidly under favorable conditions
of moisture and temperature. The causal organism
can gain entrance only through a wound or bruise.
Rough handling of the crop during hauling and stor-
ing therefore opens the way to heavy infection and
consequently loss from soft rot.
The Organism. The Bacillus is rod-shaped, long
or short, and usually formed in chains. It moves
about by peritrichous flagella. It completely lique-
Family Cruciferz 193
fies gelatine in about six days. Gas is produced with
a majority of strains.
Control. The greatest loss in storage occurs where
the temperature is maintained much above the freez-
ing point and where the facilities for ventilation are
poor. Toremedy this, the temperature, as far as possi-
ble, should be maintained one or two degrees above
freezing. Thecropshould be thoroughly dried and ex-
posed to the sunlight before being entered into storage.
Diseased fields should be rotated to other crops.
DAMPING OFF
Caused by Olpidium brassice (Worr.) Dang.
The symptoms of damping off are similar to those
produced by Pythium de Baryanum, p. 43. The
sporangia of the parasite may be found singly or
in groups in each infected host cell. The zoospores
are globose, uniciliate. The resting spores are
globose, wrinkled, and star-like in appearance.
The disease is found mostly in seed beds, where it
does considerable damage. For methods of control
see p. 43.
WHITE RUST
Caused by Cystopus candidus (Pers.) Lev.
White rust of cabbage is seldom troublesome
enough to attract attention. The symptoms of the
disease are the same as on other cruciferous hosts
such as mustard or radish, p. 211.
13
194 Diseases of Truck Crops
Downy MILDEW
Caused by Peronospora parasitica (Pers.) De By.
Downy mildew, while a common field disease,
causes considerable damage to young seedlings.
It is characterized by whitish downy patches on the
under side of the leaf. Seen from above, the af-
fected areas are angular, pale yellow, and somewhat
shrunken. The spots seem to be limited by the
veins of the leaf. The disease is common in damp
weather. Besides the cabbage, cauliflower, radish,
turnips, and numerous other cruciferous hosts are
known to be susceptible to downy mildew.
The sporophores of the fungus are stout and
numerously branched, each branch repeatedly forked.
The tips of the smaller branches are slender and
curved. The conidia are broadly elliptical, and the
resting spores are globose and smooth, becoming
wrinkled with age.
In the seed bed or in the field, spraying with
4-4-50 Bordeaux will control the disease. The first
application should be given as soon as the disease
makes its appearance. Later the application will
be governed by weather conditions.
Drop
Caused by Sclerotinia lhbertiana Fckl.
Drop is a disease fairly common on cabbage. The
trouble may be recognized by a drooping and wilting
Family Cruciferz 195
of the leaves. The bases of the affected foliage are
covered with a white weft of mycelial growth, later
by sclerotia. For a more extended discussion of the
disease see lettuce drop, p. 143. -
BLACK LEG OR Foot RoT
Caused by Phoma oleracea Sacc.
Black leg, first noticed in the United States by
Manns! in Ohio, was undoubtedly introduced here
from Europe.
Symptoms. The disease is usually manifested in
the seed bed about two to three weeks before trans-
planting in the field. The trouble at first appears
as white elongated sunken lesions on the stem and
below the leaf attachment (fig. 30f). Scattered over
the lesions are minute black specks which constitute
the pycnidia or fruiting sacs of the fungus (fig. 30 i
and j). Infected seedlings usually collapse and take
on a bluish color. In the field, the foliage of the
older but affected plants (fig. 30 h) usually take ona
mottled, metallic, bluish-red color at the margins,
and the lower outer leaves wilt. On examining such
plants there will always be found sunken lesions
(fig. 30 g) which often girdle the foot of the plant.
In wet weather affected plants attempt to produce
new roots above the infected area, which, however,
are never able sufficiently to support the plant.
Foot rot is often confused with forms of injury
brought about by maggots.
* Manns, T. F., Ohio Agr. Expt. Sta. Bul., 228: 255-297, IgII.
196 Diseases of Truck Crops
Treatment. Manns recommends treatment of the
seed bed with 4-4-50 Bordeaux to be applied im-
mediately after planting, at the rate of one gallon to
each ten square feet of bed space. The bed is again
sprayed with Bordeaux about two weeks before and
once again at transplanting.
BLack MoLp
Caused by Alternaria brassice (Berk.) Sacc.
Black mold is a serious disease of the cabbage in
the Southern States. It also attacks collards.
Symptoms. Affected leaves are covered with
spots which are nearly black on the under side of the
leaf. The spots are composed of a series of rings,
the smaller ones enclosed within the larger (fig. 31 a).
There is no distinct border separating the diseased
from the healthy, the spots gradually shading off
into the healthy tissue. Little is known of the causa-
tive fungus or of the control of this disease. It is
probable that spraying with 4-4-50 Bordeaux will
be of value.
LEAF SPOT
Caused by Cercospora bloxami B. and Br.
Leaf spot is of little economic importance. It only
attacks the leaves of weak or languid plants. The
spots are pale, somewhat circular, surrounded by a
slightly raised, faintly purple border. The conidial
FIG. 31. CABBAGE DISEASES.
a. Alternaria black mold, b. cabbage seedlings growing in a cabbage sick soil
which has been steam sterilized, c. sick cabbage seedlings in a cabbage sick soil,
(after Jones and Gilman), d. an old wilt infected cabbage plant: notice bare stalk,
e. conidia of Fusarium conglutinans, f. clamydospores (resting spores), of F. con-
glutinans, g. wilt infected cabbage seedlings: notice how the leaflets drop off as a
result of the disease.
Family Cruciferze 197
tufts are prevalent in the center of the spots, and are
pale brown and sparingly septate. The conidia are
long clavate, tapering, straight to curved, many sep-
tate, and hyaline to faint smoky color.
WILT OR YELLOWS
Caused by Fusarium conglutinans Woll.
There is no other cabbage disease that is economi-
cally so important as wilt. This trouble is threaten-
ing the cabbage industry in many parts of the United
States. In the cabbage centers of Ohio and Wiscon-
sin, truckers lose so heavily from wilt, that in many
sections, the growing of the crop has been made very
unprofitable.
Symptoms. Theterm “‘yellows’’ well describes the
disease. Affected seedlings are yellowish and stunted
in growth with a tendency to drop their lower leaves
at the least touch (fig. 31 g). Such plants when
transplanted in the field either die outright or make
very slow growth. The symptoms in the older
affected plants are the same as on the seedlings.
The outer leaves turn yellow and drop off one by one,
until a bare stump and top head are left (fig. 31 d).
Usually the plant is uniformly attacked; but the in-
fection may be confined to one side. This one-sided
check results in the lateral warping and curving of
the stems and leaves. Under field conditions, high
temperatures are very favorable for the spread and
development of yellows.
The Organism. The best description of Fusarium
198 Diseases of Truck Crops
conglutinans Woll. is given by Gilman.‘ Sporo-
dochia, lacking or greatly reduced, pionnotes never
present, conidia borne on short conidiophores strewn
throughout the mycelium. The majority of spores
are non-septate, a few are one to three septate
(fig. 31 e); conidia with higher septation are rare.
In old cultures, chlamydospores are produced in
great abundance (fig. 31 f).
Control. Cabbage yellows cannot be readily
controlled. Naturally a clean seed bed should be
chosen (fig. 31 b-c). However, the healthy seedlings
when transplanted into infected fields will soon con-
tract the disease. ‘The same also holds true even
when the seeds are disinfected. Neither is crop
rotation a sure method of control. It is doubtfulif
fifteen years’ rest from cabbage will free a soil from
the causative parasite. The best method of control
is the development of resistant varieties. This has
already been accomplished by Jones and Gilman?
who selected a strain from the Hollander which
they named Wisconsin Hollander No. 8. This strain
is said to be nearly 100 per cent. resistant to wilt. The
same is also true for the Volga (fig. 32 a-b). The
question arises as to whether a cabbage selected for
resistance under Wisconsin soil will show it in a like
degree in other climatic conditions and soil. For
the cabbage the answer may be given in the affirma-
tive. For instance, the Houser and the Volga, which
: Gilman, J. C., Annals Missouri Bot. Garden, 3 : 2-84, 1916.
? Jones, L. R., and Gilman, J. C., Wisconsin Agr. Expt. Sta. Bul.,
38 : I-69, 1915.
Fic. 32. CABBAGE DISEASES.
a. Two rows of Volga, a highly resistant commercial cabbage growing ina
cabbage sick soil (yellows), b. resistant cabbage strains in a cabbage sick soil
(a. and b. after Jones and Gilman).
Family Cruciferze 199
have proved wilt proof in Maryland, have proven
equally resistant under Wisconsin conditions. It is,
however, advisable to grow seed in the same locality
where the resistant cabbage has been developed.
The method of developing resistant varieties is
given more fully on p. 374.
Root Knot
Caused by Heterodera radicicola (Greef) Mill.
Root knot is very widespread in the Southern
States, but is confined mostly to the light sandy soils.
It is often mistaken for club root. Careful observa-
tion will show the differences. Root knot is char-
acterized by small swellings on the lateral feeding
roots. For a description of the parasite and meth-
ods of control see p. 49.
DECAY OF CABBAGE IN STORAGE
Not all field-grown cabbage is consumed when
harvested. 52-53, 1917.
346 Diseases of Truck Crops
The greatest amount of rotting occurs within the
fruit.
The Organism. The parasite is a typical yeast.
It produces arthrospores of non-gametic origin, asci
of gametic origin (fig. 65 a-c). The ascospores are
formed in two groups of four each, slender, one-
septate, and each containing a motionless flagellum.
Little is known about the control of this disease.
Fruit Rot
Caused by Phoma destructiva Plowr.
Fruit rot is found in Cuba, Florida, South Carolina,
Kansas, and New York. If not checked, it will no
doubt spread rapidly and add to the burdens of losses
from other troubles.
Symptoms. On the fruit the disease is charac-
terized by conspicuous dark spots (fig.65 e) on the
side and at the stem end of both green and mature
fruit. On the surface of the largest spots numerous
dark pycnidia may be seen. Besides attacking the
fruit, the disease may also attack the foliage, causing
dark spots which resemble those on the fruit (fig.
65d). Affected leaves shrivel, droop, and sometimes
drop off. The disease seems to be unable to attack
potatoes or peppers.
The Organism. The mycelium (fig. 65 h) forms a
dense network of fungal threads within the host
tissue. The pycnidia (fig. 65 g) are subglobose, car-
bonaceous, smooth, slightly papillate, and with a dis-
tinct central pore. The pycnidia are scattered and
Fic. 65. Tomato DISEASES.
a. Various forms of vegetative cells of the yeast rot fungus, b. ascus, -. ascospores
of the yeast rot fungus (a. to c. after Schneider), d. Phoma rot on foliage, e. Phoma
rot on fruit, f. pyenidium of the Phoma rot organism, g. cross-section of a pyenidium
of the Phoma fungus, h. mycelium, 7. pycnospores of same (d. to i. after Jamieson).
QU OV A oy i } ~
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Fic. 66. TOMATO DISEASES.
a. Septoria leaf spot, b. section through a pycnidium of Septoria lycopersici
(after Levin), c. section through acervulus of Colletotrichum phomoides (after Venus
Pool), d. and e. Melanconium rot, f. section through an acervulus of the Melan-
conium fungus (d. to f. after Tisdale).
Family Solanacez 347
possess a thin wall; the pycnospores (fig. 65 i) are
hyalin and one-celled. Jamieson’ failed to find an
ascus or winter stage. Should the disease become
serious, spraying with Bordeaux is recommended.
LEAF SPOT
Caused by Septoria lycopersici Speg.
The disease is generally known as late blight, or
blight, both of which names are misleading. Recent
investigations by Levin? confirm the belief that leaf
spot is widely distributed. It is found in Alabama,
California, Connecticut, Delaware, Illinois, Louisiana,
Massachusetts, Maryland, Michigan, Missouri, New
Jersey, New York, North Carolina, Ohio, Penn-
sylvania, Virginia, Tennessee, Texas, and Wisconsin.
Symptoms. The first indications of the disease
are minute water-soaked spots on the underside of the
leaves. With time these increase in size and become
circular in outline with a definite margin (fig. 66 a).
The spots become hard, dry, dark, and shrunken, and
when numerous they coalesce into large blotches, in-
volving the entire leaflets and leaves; the latter soon
droop, dry, and cling to the stalk, until broken off by
the wind or by any other jar. Within the spots are
formed minute black glistening pycnidia and the
spores exude as yellowish mucilaginous drops.
On the stems the spots are similar to those on the
leaves, although they are not so clearly defined, nor
t Jamieson, C. O., U.S. Dept. Agr. Research, 4 : 1-20, 1915.
? Levin, E., Michigan Agr. Expt. Sta. Tech. Bul. 25 : 7-51, 1916.
348 Diseases of Truck Crops
do they work in deep to form cankers. Spots may
also occur on the calyx and on the fruit. The dis-
ease, however, is usually a foliage trouble. Of the
more resistant varieties may be mentioned Mikado,
King Humbert, Wonder of the Market, and Up to
Date. Of the medium resistant varieties may be
mentioned Alice Roosevelt, President Garfield, Pre-
lude, Ponderosa, and Magnum Bonum. The Trophy
and Ficarazzi are very susceptible varieties.
The Organism. ‘The mycelium of Septoria lyco-
persici is hyalin, septate. The pycnidia are globose
(fig. 66 b) ; the pycnospores are hyalin, needle-shaped,
many-septate, and lose their vitality when exposed to
ordinary room temperature for about four days.
Control. The disease often starts on the seedlings
in the seed bed. It is important therefore to start
with a clean seed bed soil. Seedlings should be
sprayed with 4-4-50 Bordeaux before being trans-
planted. In the field the plant should not be worked
in wet weather, or when covered with dew. Spraying
with 4-4-50 Bordeaux is recommended, especially in
wet weather. Since the causative fungus is carried
over in pycnidia on dead leaves or stems, the burn-
ing of all trash becomes necessary.
ANTHRACNOSE
Caused by Colletotrichum phomoides (Sacc.) Chester.
Anthracnose is a disease to which ripe tomatoes
are especially subject. The losses are often consid-
erable both in the field and in transit.
ee eS
ee oP ee
|
Family Solanacez 349
Symptoms. ‘The spots are at first small, but they
soonenlarge. They are discolored, sunken, wrinkled,
with distinct central zones, closely resembling the
anthracnose of apple. In moist weather the spots
become coated with a salmon-colored layer which
consists of the spores of the fungus.
The Organism. In structure C. phomoides is little
different from other Colletotrichums. The setz of
the fungus are very numerous, thus giving the acer-
vuli a black appearance. The conidiophores are
short, and the conidia, oblong, hyalin, and one-celled
(fig. 66 c).
Control. Anthracnose depends upon wet weather
for its activity. Spraying with Bordeaux is recom-
mended.
MELANCONIUM ROT
Caused by Melanconium Tisdale Taub.
Melanconium rot is a disease which attacks tomato
fruit. Tisdalet was the first to call attention to this
trouble which he attributed to a species of Melan-
conium. The writer has often had occasion to col-
lect this disease on tomatoes in the Bryan (Texas)
market. The origin of the fruits could not be exactly
ascertained, but they were supposed to come from
Florida, while others were home-grown.
Infection experiments by the author affirm the
parasitic nature of the organism, which is tempor-
arily named Melanconium Tisdale Taubenhaus.
* Tisdale, W. H., Phytopath. 6 : 390-394, 1916.
350 Diseases of Truck Crops
Symptoms. The disease is found both on partly
green and on ripe fruit. The spots are brown to
black, small, irregular, somewhat sunken, dry, and
superficial, with the centers slightly raised (fig. 66
d-e).
The Organism. The mycelium is white, much
branched, and closely septate, the septation however
being largely influenced by food supply. The co-
nidiophores are straight, short, closely packed to-
gether, arising from a basal pseudostroma (fig. 66 f).
The conidia are borne singly at the apex of each co-
nidiophore. The conidia are Phoma-like, minute,
cylindrical, slightly rounded at both ends, greenish
white in color, and germinate by means of a single
germ tube produced at either end.
Control. Nothing seems to be known of the control
of this trouble. Little is known of its distribution.
But since it has been found in Wisconsin by Tisdale,
and in Texas by the writer, it seems to be of wider
distribution than is generally recognized. Possibly
it is usually mistaken for other tomato troubles.
LEAF Mop
Caused by Cladosporium fuluum Cke.
Leaf mold is a tomato trouble which is very
troublesome under greenhouse conditions. In some
of the Southern States, however, it is found on field
tomatoes. The disease is favored by damp, muggy
weather.
Symptoms. The mold appears as rusty cinnamon,
|
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.
z
{
|
a
:
FiG.67. TOMATO DISEASEs.
a. Cladosporium leaf mold, b. conidiophores of Cladosporium fulvum, c. conidia of
C. fuluum, (b. and c. after Southworth), d. two plants artificially infected with
Sclerotium Rolfsii, e. sunburn, f. Macrosporium rot.
Family Solanaceze 351
irregular, feltlike spots on the underside of the leaf
(fig. 67 a), the upper part of which turns brown, then
black, and the affected foliage finally curls and dies.
Control. Careful spraying with Bordeaux mixture
will help to keep it in check.
BLACK ROT
Caused by Macrosporium solani E. and M.
Black rot is a fruit trouble commonly found in dry
weather and generally attacking ripe tomatoes.
The spots are black, dry, slightly wrinkled, and ex-
tending deep into the interior tissue (fig. 67 f).
_ The mycelium of the fungus is at first hyalin to
brown, then black. The conidiophores and conidia
are dark, with three to six transverse and one to two
longitudinal septa.
SLEEPING SICKNESS
Caused by Fusarium lycopersici Sacc.
Sleeping sickness is one of the most serious of
tomato troubles. It is prevalent in New Jersey,
Delaware, Maryland, Virginia, and in nearly every
Southern State.
Symptoms. Infected plants become pale, the
leaves wilt and droop and never recover (fig. 68).
The droopiness of a diseased plant gives it a sleepy
appearance, hence the name of the disease. On
splitting open a diseased root or stem, the interior
vascular bundles will be found to be brown.
352 Diseases of Truck Crops
The Organism. F. lycopersici is a soil fungus
which may be introduced with infected manure or
seedlings. The fungus greatly resembles F. oxy-
sporum. ‘The conidia are hyalin to yellowish, fal-
cate, acute:
Control. Spraying will not control this malady
since the parasite lives internally and cannot be
reached by external applications. Long rotations
in which the land is given a rest from tomatoes are
recommended for at least ten years. The selection
of resistant varieties may offer a means of conquering
this trouble.
YELLOW BLIGHT
Caused by Fusarium orthoceras App. and Woll.;
Fusarium oxysporum Schl.
This disease is common on tomatoes in the Pacific
Northwest. It has been investigated by Humphrey*
and found by him to be caused by the two species of
Fusaria above mentioned.
Sympioms. It does not usually manifest itself
until late, when the plants are blooming, or even
when the fruits are partly formed. At first there is
a slight twisting of the entire leaf, accompanied by a
purpling of the veins. This is also followed by a
rolling inward, and by drooping, but not wilting, of
the leaflets and leaves. The foliage then take on
glaucous greenish color, the fruit ripen prematurely,
* Humphrey, H. B., Washington Agr. Expt. Sta. Bul. 115 : I-22,
1914.
EEDA, Oe pa” 4
OMATO.
+
fl
SLEEPING SICKNESS OF
Os.
Tic.
Family Solanacez 353
but the pulp lacks in flavor and taste. Affected
plants cease growing, exhibit a thin, spindly growth,
and cease producing. The disease is confined to the
root system, which is slowly destroyed; it becomes
most virulent with the high temperatures. Both
Fusarium orthoceras and F. oxysporum also induce
a disease on the potato, see p. 327.
Control. Both Fusaria produce an abundance of
chlamydospores in the soil, thus making the eradica-
tion of the disease very difficult. Long rotations
seem to have no effect in controlling the trouble.
Injuring the rootlets at transplanting seems to in-
crease the amount of diseased plants. Definite
methods of control are as yet lacking.
RHIZOCTONIA FRUIT ROT
Caused by Corticium vagum B. and C. var. solani
Burt.
This form of rot makes its appearance at the place
where the fruit touches the ground. The diseased
area becomes chocolate-colored, and the epidermis
slightly wrinkled. The rot extends into the interior
pulp turning it brown and dry. For further descrip-
tion of the causative fungus, see p. 45.
SOUTHERN BLIGHT (fig. 67 d), see PEPPER, p. 305.
Root Knot, see NEMATODE, p. 49.
23
CHAPTER XXII
FAMILY UMBELLIFER
Tuts family contains trucking crops which are of
considerable economic importance. Of these may
be mentioned the carrot, celery, parsley, and parsnip.
According to the Thirteenth census of the United
States, the area devoted to carrots in the United
States in 1909 was 3764 acres, and the total crop was
valued at $473,499, with New York leading in acreage.
The area devoted to celery in 1909 was 15,863 acres,
and the total crop estimated at $3,922,848. Of the
leading celery States may be mentioned New York,
California, Michigan, Ohio, Massachusetts, and
Pennsylvania. The area in parsley in 1909 was 192
acres, and the crop estimated at $27,181. Thiscrop is
largely grown in Louisiana. The area in parsnip in
1909 was 722 acres, and the crop estimated at $102,-
674. Parsnip is grown mainly in New York, Massa-
chusetts, Illinois, and Michigan.
DISEASES OF THE CARROT (Daucus carota)
Sort Rot, see CABBAGE, p. 192.
Root Rot, see RHIZOCTONIA, p. 45.
354
Family Umbelliferze 355
DISEASES OF THE CELERY (A pium graveolens)
SOFT Rot, see CABBAGE, p. 192.
Rust
Caused by Puccinia bullata (Pers.) Schr.
This rust resembles the rust of asparagus. The
disease is unimportant, and is seldom met with in
the United States.
LEAF SPOT
Caused by Phyllosticta apii Hals.
Leaf spot is a disease of minor importance. The
trouble is characterized by dull brown patches on any
part of the leaf. Spraying for late blight will also
control leaf spot.
LATE (BRIGHT
Caused by Septoria petroselini Desm. var. apii
Br. and Cav.
Late blight is perhaps one of the worst diseases of
celery. It may be found wherever celery is grown.
In California, the greatest money losses to this crop
are attributed to late blight.
Symptoms. The disease first attacks the lower
356 Diseases of Truck Crops
leaves of the stalk, producing irregular spots without
a definite boundary line. When the spots become
numerous the foliage withers and dries up (fig. 69 a,
b, c, d). The disease attacks the leaves as well as
the stalks, rendering the affected plants useless so far
as market is concerned. In storage, plants affected
with late blight will keep very poorly or rot alto-
gether.
The Organism. The fungus mycelium is hyalin,
septate. The pycnidia (fig. 69 e) are olivaceous,
prominent, andabundantinthespots. The pycnidia
are filifom, straight or curved, hyalin, and many
septate.
Control. According to Rogers,* late blight may
be controlled by spraying with 5-6-50 Bordeaux.
The first two applications should be given the
seedlings in the seed bed. In the field the first
spraying should be given about six weeks after trans-
planting and continued once a month until the rainy
season is over. With the advent of heavy rains,
spraying should be done once every two weeks.
Besides spraying, shading also seems to keep the
disease in check. In spraying celery great care
should be exercised to use a sprayer which is operated
by a pressure of not lessthan 150 pounds. Where this
is overlooked, large drops of the Bordeaux mixture
may be deposited on the leaves and stalks, which upon
drying may deposit copper salt sufficient to harm
the consumer. Sprayed celery should be carefully
washed and dried before shipping.
t Rogers, S. S., California Agr. Expt. Stat. Bul. 208 : 83-115, 1911.
Fic. 69. CELERY DISEASES.
a. Septoria leaf spot on leaf, b. Septoria leaf spot on leaflet, c. Septoria lesions on
celery seed, d. Septoria spots showing pycnidial bodies, e. cross section showing
pa aaa and pycnospores of Septoria petroselini (a, c, and e after Coons and
Levin).
Fic. 70. CELERY DISEASEs.
a. Cercospora leaf spot, b. conidiophores and conidia of Cercospora apitt
(after Duggar and Baily), c. Rhizoctonia root rot.
Family Umbelliferae 357
EARLY BLIGHT
Caused by Cercospora api Fr.
Early blicht is as common a disease as the late
blight. In some seasons of heavy rains it is very
destructive. It appears early and affected plants
have little value for market purposes.
Symptoms. ‘The trouble first appears on the outer
leaves as pale blotches visible on both sides of the
affected parts. The spots are irregular, angular in
outline, limited apparently by the leaf veins, with
slightly raised borders (fig. 70 a-b). The spots later
turn brown to ashy white.
Coniroi. Early blight may be controlled by spray-
ing with Bordeaux mixture as with late blight. The
Boston Market and Gold Heart should be avoided
because of their susceptibility to the disease. The
White Plume seems to be resistant.
DISEASES OF PARSLEY (Carum petroselinum)
Drop, see LETTUCE, p. 143.
LATE BLIGHT, see. CELERY, p. 355.
DISEASES OF THE PARSNIP (Pastinaca sativa)
EARLY BLIGHT, see CELERY, p. 357.
Root Rot (fig. 70 c), see RHIZOCTONIA, p. 45.
WEEDS
Of the more important Umbelliferous weeds which
truckers have to contend with may be mentioned
358 Diseases of Truck Crops
Wild Carrot (Daucus carsta), wild parsnip (Pastinaca
sativa), and poison hemlock (Cornium maculatum).
All of these weeds should be eradicated by clean cul-
ture. The first two especially help to carry the
fungus of early blight, Cercospora apii.
PART Iv
CHAPTER XXIII
METHODS OF CONTROL
From the preceding chapters the trucker will be
made well aware of the many crop diseases he has to
deal with and of the numerous methods at hand to
help him to control or keep in check most of the
troubles. The methods of control may be classified
as follows:
(1) Soil sterilization. This method has been dis-
cussed under Chapter IV, page 53.
(2) Seed treatment taken up in Chapter VII.
(3) Spraying.
(4) Crop rotation.
(5) Development of resistant varieties.
Spraying
While the orchardist has learned the necessity of
spraying, it is doubtful whether truckers have suf-
ficiently realized its value. Spraying has two aims:
to kill the insect and animal pests, and to con-
trol fungous diseases. The substances which are
used for the one purpose are without effect on the
other.
361
362 Diseases of Truck Crops
INSECTICIDES
All animal and insect pests are best controlled by
the use of poisonous mixtures applied in the form of
liquid sprays or of powders. Insecticides may be
classified as internal or stomach poisons, and external
or contact poisons.
(a) Stomach Poisons. Paris green is one of the
oldest of stomach poisons. When chemically pure,
it is composed of copper oxide, acetic acid, and arseni-
ous acid. It destroys cutworms, caterpillars, beetles,
grubs, slugs, etc. It should be applied preferably as
a liquid, using one pound of the poison and two
pounds of lime to two hundred gallons of water. It
tends to sink to the bottom of this mixture, unless
constantly stirred while being applied. This chemi-
cal is often adulterated with white arsenic, causing
it to scorch the treated plants badly. Therefore
for truck crops the use of arsenate of lead is to be
preferred, since it is less liable to scorch the foliage,
and it adheres better. Its chemical composition
consists of acetate of lead and arsenate of soda. It
is applied to the best advantage as a liquid, using
about three pounds of powdered arsenate or five
pounds of paste arsenate to one hundred gallons of
water.
Arsenite of zinc may also be used. It is a very
finely divided fluffy white powder which distributes
and adheres well to the foliage. It is intermediate
between Paris green and lead arsenate in strength,
and it costs less than either.
Methods of Control 363
It is essential when arsenicals are used to see that
they are correctly labeled, and kept under lock and key,
as they are poisonous to man and animals.
Hellebore or white hellebore is somewhat less
dangerous than the arsenicals. However, it loses
its insecticidal value by being exposed to the air.
It is a specific against slugs.
(b) Contact Poisons. All the tobacco or nicotine
products sold principally as extracts or powders be-
long to this class. A common brand much used is
the preparation known as ‘“‘Black leaf 40,”’ diluted
I part to 700 or 800 of water. An addition of
ivory soap at the rate of two bars to each 100
gallons of the solution increases its effectiveness
by making it spread out better. Aphine, sulpho
tobacco, and a number of other products found on
the market are usually valuable as contact poisons
if properly tested out and guaranteed by the deal-
ers. Ordinary laundry soap, one pound to seven
gallons of water, is very effective against all soft-
bodied sucking insects.
FUNGICIDES
These are poisons used to control fungous diseases.
As previously stated, some parasitic fungi live on the
surface of the leaves and stems and are therefore .
easily controlled. An example of this is the powdery
mildew. Other fungi, and these are in the larger
majority, are those which live parasitically within
the tissue of the host, and therefore cannot be reached
364 Diseases of Truck Crops
by any spray. Fungicides are helpful only in pre-
venting entrance of the parasite in the host. They
are as ineffective in controlling insect pests, as are
insecticides in controlling fungous diseases.
(a) Bordeaux Mixtures. This is the standard
fungicide. The strength used for tender plants is
three pounds of copper sulphate—also known as blue
stone,—six pounds of lime, and fifty gallons of water.
The easiest way to prepare it is to dissolve the blue
stone thoroughly in twenty-five gallons of water.
The best quality of unslaked lime should be used
and slaked in a little hot water, care being taken,
however, not to flood it while slaking, nor to let it
become too dry. When the slaking is completed,
enough water is added to make twenty-five gallons.
The limewater and the blue stone solution are
then mixed, pouring first one part of lime water, then
another part of the blue stone; the mixture is then
strained and used at once. With crops with delicate
foliage, such as watermelon, weak Bordeaux must be
used to prevent burning of foliage (see page 243).
For truck crops with less delicate foliage, the stand-
ard Bordeaux mixture is 4-4-—50—that is, four pounds
copper sulphate, four pounds unslaked lime, and
fifty gallons of water.
Stock Solutions.. In spraying large areas, it is not
always practical to weigh out and prepare the in-
gredients at short notice. The trucker will therefore
find it advantageous to prepare stock solutions so
that large quantities of both dissolved copper sul-
Methods of Control 365
phate and of lime may be ready for instant use. A
stock solution of blue stone may be prepared as
follows: Forty gallons of water are put into a
fifty-gallon barrel; forty pounds of blue stone are
placed in a basket and hung up so that the basket is
half covered by the water in the barrel. As the blue
stone is dissolved, each gallon of the water contains
one pound of the chemical. In another barrel may
be slaked forty pounds of fresh lime. Each gallon of
that will contain one pound of lime. By keeping the
slaked lime in the barrel covered with water and pre-
venting it from evaporating, and also keeping the
barrel with the blue stone solution covered to prevent
evaporation, we shall have stock solutions ready for
instant use. To make a 4-4-50 Bordeaux from stock
solutions, for instance, it is necessary to take four
gallons from the stock solution barrel with blue
stone, and add this to twenty-one gallons of water.
Four gallons are also taken from the stock solution
barrel of slaked lime and added to twenty-one gal-
lons of water. The two solutions of twenty-five
gallons each are now added together, thus making a
4-4-50 Bordeaux. In this way it is easy to prepare
any formula from the stock solutions. To determine
if the Bordeaux contains sufficient lime, the following
test may be carried out. A few drops of potassium
ferrocyanide are added to the Bordeaux mixture.
If sufficient lime is present, no change will take place,
but if the mixture is deficient in lime, a dark reddish
brown color will appear where the drop strikes the
liquid. This testing fluid is easily prepared by dis-
366 Diseases of Truck Crops
solving one ounce of potassium ferrocyanide in about
eight ounces of water. This chemical costs but a few
cents in any drug store and will last a long timeif
kept in a tightly sealed bottle. |
POINTS TO BE REMEMBERED
In preparing Bordeaux the following points should
be kept in mind:
(1) Copper sulphate solutions must be kept only in
vessels of wood, fiber, brass, bronze, orcopper. They
must not be kept in iron or tin vessels, as they will
corrode them.
(2) It is necessary to use fresh stone lime, as air-
slaked lime is useless.
(3) Bordeaux mixture can be used only when
freshly mixed. If allowed to stand twelve hours after
making, it loses all fungicidal value.
(4) Bordeaux mixture or lime should never be
strained through burlap. The lint of the burlap is
likely to work up into the nozzles and clog them.
(5) Undiluted solutions of copper sulphate or lime
should never be mixed together.
(6) Bordeaux mixture should not be prepared with
hot water.
~ (b) Ammoniacal Copper Carbonate. The objection
to the use of Bordeaux is that it stains the leaves
and foliage.
To avoid staining, colorless ammoniacal copper
carbonate may take the place of Bordeaux. It is
prepared as follows:
Methods of Control Oia
Cnppemmeaocnctes 802k aes Vides 2c es 5 ounces
Aaoanmnie (26. Baume) ek ee. 3 pints
VAT 2 ES aoa La et AIR MR a ay 50 gallons
The best results are obtained when the copper car-
bonate is first made into a paste with a little water.
It is then dissolved by adding the ammonia, which is
diluted with four quarts of water. If three pints
of ammonia fail to dissolve all the copper carbonate,
more may be used. Ammoniacal copper carbonate
is only effective when used fresh. It loses its fungi-
cidal value by standing, as the ammonia evaporates
quickly.
(c) Sulphur. Flowers of sulphur are often used to
control powdery mildew or asparagus rust. It may
be applied either by hand or with a duster. There
are a number of other fungicides on the market which
are not mentioned here. They should be thoroughly
tested before they are used. Considerable discretion
should be exercised before using a new fungicide
which claims to be a ‘‘Cure all.”’
COMBINATION SPRAYS
In the foregoing chapters on diseases, it was seen
that truck crops are subject to the attacks of more
than one malady. Moreover, truck crops are also
subject to the attacks of insect pests. It is therefore
advisable to control both insect pests and fungous
diseases at the same time. Spraying, if properly
368 Diseases of Truck Crops
done, is effective in controlling or in keeping in check
all the pests which attack truck crops. In combining
a fungicide with an insecticide, we may accomplish
two aims in one operation. The various spray mix-
tures which may or may not be combined are in-
dicated by Cooley and Swingle? as follows:
Tobacco Bordeaux
extracts mixture
Paris green yes yes
Arsenate of lead yes yes
Arsenite of zinc (ortho) yes no
Arsenite of lime yes yes
Each of these preparations is mixed and applied just
as if it were used alone. A combination of the am-
moniacal copper carbonate with an arsenate would be
unsafe, since the ammonia renders the arsenic more
soluble, and hence may result in the burning of the
foliage. However, it may be safely mixed with the
tobacco products.
Recent investigations by Professor Safro, Entomo-
logist to the Kentucky Tobacco Products Co., indi-
cate that ‘‘Black leaf 40’’ may be used in combination
with such spray chemicals as lime-sulphur, arsenate
of lead, arsenite of zinc, and iron sulphate, for con-
trolling sucking and chewing insects and fungous dis-
eases, the soap in this case being omitted. Professor
Safro’s work further claims that ‘‘ Black leaf 40’’ may
*Cooley, B. A , and Swingle, D. B., Montana Agr. Expt. Sta. Circ.
17: IIQ-I5I, 1912.
Methods of Control 369
be safely combined with Bordeaux, and the desired
results obtained. He writes as follows: ‘‘For pur-
poses of spraying, add to every one hundred gallons of
Bordeaux three fourths of a pint of ‘Black leaf 4o.’
As far as safety to the foliage is concerned, much
greater strengths of nicotine may be added to the
Bordeaux, but no additional effectiveness will be
given to the mixture as an insecticide. Anynicotine
solution which contains four hundredths of one per
cent. nicotine will be effective in controlling plant lice,
provided, however, the work is thoroughly done.’’
PROPORTIONS OF COMBINED SPRAYS
Bordeaux and Paris Green
Pans Green koi ea ek 1% pound
Bordeaux mixture. .....50 gallons
Bordeaux and Arsenite of Soda
Arsenite of Soda...) 2... I quart
Hordeaux mixture sy.\.'... 50 gallons
Bordeaux mixture must never be combined with
kerosene emulsion, carbolic acid emulsion, and mis-
cible oils.
(d) Potassium Sulphide. Like sulphur this is a
valuable fungicide for the control of the powdery
mildew. The following strength is recommended:
24
370 Diseases of Truck Crops
Potassium sulphide is effective only if used imme-
diately it is prepared. It loses its value by being
exposed for any length of time.
STICKERS
It is well known that with some plants, such as
cabbage, spray mixtures cannot be made to stick.
The use of a sticker added to the spray mixture will
largely overcome this difficulty. A sticker may be
prepared as follows:
Resim Naor h omen. 2 pounds
Sal Soda (crystals)...1 pound
Wratetocvouec cas. siaeallon
The resin and the sal soda should be added to one
gallon of water and boiled in an iron kettle for one
and a half hours until clear. For plants which are
hard to wet, such as cabbage, or onions, the amount
of the sticker given above should be used for each
fifty gallons of Bordeaux or ammoniacal copper car-
bonate. For other plants, this amount is added to
each one hundred gallons of the spray mixture.
PRINCIPLES INVOLVED IN SPRAYING
It should be remembered that to destroy chewing
insects, such as caterpillars, etc., the stomach poison
must be evenly distributed all over the plant. This
thorough spraying should be done as soon as the
presence of the pest is suspected. Intelligent and
observant growers will remember the time of ap-
Methods of Control 371
pearance of the pest every year, although this date
depends somewhat on the climate of each season.
In destroying the green aphids, the contact poison
should be distributed as evenly as possible on the
insect itself. It is, therefore, best to spray for aphids
when they are actually found working on the plants.
To check chewing insects and fungous pests, however,
the applications are made before the parasites appear.
Before spraying it is necessary to have well in mind
which organism is to be destroyed, and the proper
ingredients to be used. To keep fungous pests in
check it is necessary to have the plant covered with
the fungicide all the time infection is feared or sus-
pected. This spraying is preventive, protecting the
plant from becoming infected. When the parasite
has penetrated the host, spraying is of little value in
saving the infected plant, although it will protect
others which are as yet healthy. It is essential that
the trucker be always ready to spray. Sometimes
retardation for even a day may prevent the attain-
ment of positive results. The timely destruction of
one insect, or of one spore, means the destruction of
countless generations of these pests.
Thoroughness is as important in spraying asit isin
everything else in life. Especially is this true for the
control of fungous diseases.
SPRAYING MACHINES
Success in spraying often depends on the sprayer,
and especially on the nozzle. In small scale garden-
372 Diseases of Truck Crops
ing, an ordinary knapsack or barrel sprayer (fig. 71 a)
will answer the purpose. For trucking on large
areas the use of power sprayers (fig. 71 b) becomes
necessary. It is difficult to recommend the use of
any one type when there are so many models on the
market. After consulting various catalogues and
examining types of spray machines at the county
fairs and other exhibits, the grower will be in a posi-
tion to determine the kind of apparatus best adapted
for his conditions. A good power sprayer should be
capable of maintaining a pressure of at least one
hundred pounds while the nozzles are open. The
sprayer should also have a convenient attachment for
spraying four rows or more, and should also possess
a device by which each row can be sprayed with
either single or double nozzles. Moreover, all the
working parts must be easily accessible, simple, and
solidly built.
CARE OF THE SPRAYING MACHINE
After each spraying the outfit should be emptied
and carefully cleansed with water. Failure to do
this will result in the corroding of the tank, rods, and
nozzles.
Crop ROTATION
Many of the soil diseases, such as root knot, Fusar-
ium wilts, etc., may be economically controlled by
crop rotation. If a certain disease gains a foothold
in the soil, it is likely to become progressively serious,
Fic. 71. SPRAY MACHINERY.
a. A hand power pump, b. a power machine, rear view, showing
arrangement for spraying three rows of cucumbers (after W. A. Orton).
Methods of Control 373
as the particular crop which the disease attacks is
grown for a number of years on the same field, the
soil becoming thoroughly permeated by the mycelium
and spores of the parasitic organism. If the infected
land is planted with crops not subject to the disease,
the parasitic organism will sooner or later die for
want of a suitable host tolive upon. For this reason
crop rotation plays an important part in the control
of numerous truck crops. To meet with success
in rotation, the trucker must know what crops are
subject to the disease to be controlled, so as to avoid
them temporarily in the sick land. Weeds, too, are
often subject to the same diseases as the cultivated
crops. Crop rotation often fails if we overlook the
importance of clean culture.
VARIETIES RESISTANT TO DISEASE
It is a well-known fact that not all varieties of
plants are alike subject to the same disease. In
going over a diseased field, we find that while a large
percentage of the plants may be dying, some few
individuals will stand up and thrive in spite of the
disease. If these individual plants are perpetuated
in the same sick field, we may succeed in developing
a strain or variety of plant which will produce one
hundred per cent. healthy individuals in the same sick
soil. On this principle are based the selection and
development of resistant varieties. Much has al-
ready been accomplished in this direction and still
more is to be expected in the future.
374 Diseases of Truck Crops
How to Develop a Resistant Variety
This may be accomplished by selecting, from the
sickest piece of land on which the crop is growing, the
healthiest individuals, and taking the seed from them.
The following year the selected seeds are again
planted on the same infected land. The best in-
dividual plants from this sowing are selected and their
seeds saved. By continuing this method of selection
for a number of years it may be possible to develop
a strain which will yield one hundred per cent. of
healthy plants in a sick soil. To maintain the purity
of the selected strain as well as its resistance, it is
necessary to reserve a plot of the sick soil, upon which
the selected strain is grown for seed purposes. Care
must be taken toward carrying any of the sick soil
of this plot to other parts of the field.
Drawbacks. With some crops and with certain
diseases it seems hopeless to try to develop a resist-
ant strain. If a variety is resistant to one disease
it may be susceptible to several others, which are
perhaps more serious. The resistance may often be
local, in which case it becomes necessary to develop
resistant types for each local condition. Resistant
varieties often may not embody the requirements of
the market. Nevertheless, the development of re-
sistant strains should be tried wherever it gives
any promise of success.
‘CHAPTER XXIV
CONTROL OF INSECT PESTS BY NATURAL FACTORS
IN this discussion we shall consider very briefly
the natural factors which help in the control of
parasitic insects.
(a) Beneficial Predacious Insects. It is fortunate
that nature always provides its own remedies. If
insect pests were not kept in check by natural enemies
the trucker who does not spray would be faced by
tremendous odds in attempting to raise crops. The
natural and beneficial enemies may be grouped, first,
into parasites which develop within the body of the
host, and second, predacious or those which feed
externally.
1. Of the first group may be mentioned a small
wasp-like insect, Lysiphlebus testaceipes. ‘This is no
doubt an important parasite, which greatly helps to
keep the green Aphis in check. Its life history was
originally worked out by Webster, * and may be briefly
summarized as follows:
A mature female thrusts her ovipositor into the
upper side of the Aphis and deposits a single egg
U.S. Dept. of Agr. Bur. of Entomology Bul., 110, 1912.
375
376 Diseases of Truck Crops
within its body (fig. 72 c-d). The egg of Lysiphlebus
hatches and soon begins to feed on the vital parts of
the Aphis. The latter gradually ceases activity and
finally dies and becomes mummified. When the
larva of Lysiphlebus reaches maturity and pupates, it
emerges through a circular lid cut on the back of the
dead Aphis. Lysiphlebus is not active at tempera-
tures below 56 degrees F.
2. Of the parasites which feed externally on
Aphids may be mentioned the lady-bird beetle, of
which there are several species. These actually de-
vour great numbers of plant lice. Lady beetles
need no description, as they are well known to all
truckers. There are, of course, other important
beneficial insects such as the Syrphid and the lace-
winged flies. For a further description of these the
reader should consult Webster’s original publication
already cited.
(b) Beneficial Fungus Parasites. There are numer-
ous species of fungi which from an economic consider-
ation are very important. These live parasitically
on numerous insect pests and undoubtedly greatly
help in keeping them in check. Of these may be
mentioned species of Empusa, and of Acrostalagmus,
which live on Aphids or plant lice. Fungi which
belong to species of Aschersonia are parasitic on the
white fly. The fungus Botrytis rileyi is parasitic on
numerous caterpillars. The fungus Cordyceps (fig.
72 a-b) contains some important species which are
parasitic on the Harlequin bugs and other insect
pests. The green muscardine fungus Metarrhizium
Fic. 72. PARASITIZED INSECTS. —TREATMENT OF FENCE Posts.
a. Cabbage bug parasitized by Cordyceps nutans, b. cabbage bug parasitized by
Cordyceps sobolifera (a. and b. after Lloyd), c. watermelon aphids parasitized by
Lysiphlebus testaceipes, showing circular holes on the backs of the aphids through
which parasite emerged, d. a female of L. testaceipes in the act of laying her eggs in
the back of a green aphis (after Webster), e. Creosoted post after a period of service,
1. a willow post treated 4 hours in hot creosote and 10 hours in cold; set June 13,
1905, examined November 1, 1914, and showing practically no deterioration after
91% years’ service. 2. A split soft maple post treated 4 hours in hot creosote and
10 hours in cold; set in 1905 and examined November 15, 1914. The post was set
below the creosote line and some decay has entered beneath the creosote shell. 3.
A 5-inch split cottonwood post given a creosote bath treatment, set in 1905 and
examined in 1914. The post shows practically no decomposition in either top or
bottom. 4. An 8-inch ash post split in half, given butt creosote treatment of 6
hours in hot and 12 hours in cold, set 1905 and examined in November, 1914. The
creosoted bottom is sound, penetration on the heart wood surface was less than in
the sap wood. The heart wood portion of this post will undoubtedly give away first.
The untreated top is in excellent condition. 5. A 44-inch untreated white cedar
post after standing 91% years. f. A small treating tank in operation. (e. and f,
after McDonald).
Natural Factors Controlling Pests 377
antsoplie is parasitic on numerous grubs and beetles.
Most of these fungi, however, are only active during
warm moist weather and cannot always be depended
upon with certainty.
CHAPTER XXV
TREATMENT OF FENCE POSTS
WHETHER trucking on a large or small scale, fence
posts are always used to protect the crops from pas-
turing animals or undesirable marauders. In buy-
ing fence posts, the aim should be to secure those
which naturally last longest. Posts of willow,
cottonwood, or soft maple will last far less than those
of red cedar, osage orange, or the mulberry. Posts
made largely of sapwood will rot much faster than
those made of heartwood. All posts, before being
used, should be rid of all their bark. The latter usually
harbors insect and fungi which when active hasten
destruction or decay. In order to preserve the life
of fence posts longest, they should be treated with
some good standard preservative. Creosote is the
most important preservative for fence posts (fig. 72 e,
I to 5). On a moderate scale, tanks (fig. 72 f)
four feet high, three feet in diameter, and capable
of holding thirty-five 41!4-inch posts should be
used. The tank is raised about one foot above the
ground to provide room for the fire box. The creo-
sote is poured in the tank and the posts are allowed
to remain in the hot preservative for a period of from
two to six hours. The posts may then be allowed to
378
Treatment of Fence Posts 379
remain in the tank until the preservative cools off,
or it is immediately transferred to another tank which
contains cold creosote. This cooling off is necessary,
as it causes a contraction of the remaining air and
moisture in the wood structure. This causes addi-
tional preservative to be drawn into the wood.
Fence posts may be treated at any time of the year.
The time of the year posts are cut affects only the
seasoning, but not its durability. Posts cut in the
winter are more difficult to peel. Contrary to general
belief, winter cut posts contain more moisture and
hence require longer seasoning. All posts to be
treated must have all the bark removed. If the
posts are cut in the spring, the peeling of the bark
is very easy. Beveling the tops of treated posts
is also recommended. This is especially necessary
when the posts are treated at the butt end which
is stuck in the ground.
dal Addlael da. i oi VR Oe ery 2 a a ee
TAM Cee P A PETE fire sD MR a Ham rt athe dabaihlsrid Dah 7 wha) i 4%
GLOSSARY
A
ACERVULI. Small groups of mycelial tufts upon which
fungus spores are formed.
ZCIDIOSPORES. Spores of the rust family formed in an
zecidium.
ACIDIUM (ecium). A cup-shaped body in which are
formed the spring spores of certain rust fungi.
AEROBE. Organism requiring air, more especially oxygen.
AMMONIFICATION. The formation of ammonia at the
expense of other forms of nitrogen compounds, by
the action of microérganisms upon organic sub-
stances.
AMMONIFIERS. Microdrganisms capable of transforming
nitrogen compounds into ammonia.
AMCBOID. Like an amoeba, the creeping movement
of which is made possible by appendage-like bodies.
ANTHERIDIUM. The male sexual organ in fungi.
APICAL. Terminal formation at the point of any struc-
ture.
ARTHROSPORES. Whole vegetative cells of either bac-
teria or fungi, which by a thickening of their walls
become resting spores.
ASCOSPORES. Spores formed in an ascus.
ascus. A sac-like structure in which the winter spores
of certain fungi are formed.
381
382 Glossary
B
' BASIDIOSPORES. Spores formed on basidia.
BAsIpIuM. A straight stick-like spore bearing fungal
thread.
C
CANKER. Definite dead area in the bark of stems or
roots of plants.
CAPITATE. Possessing a head.
CARBONACEOUS. Dark to black colored.
CHLAMYDOSPORES. Resting spores with very thick
walls, formed within mycelial cells.
CHLOROPHYLL. Green coloring matter in leaves of the
higher plants.
CHROMOGENIC. Producing color.
CILIATE. Fringed with hairs.
COLUMELLA. Sterile axle of a pillar-like structure within
a sporangium.
CONIDIA. Spores formed asexually.
CONIDIOPHORE. A spore-bearing fungal stalk.
CONSTRICTED. Drawn together or contracted.
CORTEX. Outer bark.
CUTICLE. The outermost skin of plants.
cyst. Sac or cavity.
D
DELIQUESCENT. Dissolving or melting.
DIFFUSE. Loosely spread.
DILATED. Enlarged.
E
ENDOSPORE. Spore formed within another cell.
ENTOMOGENOUS. Living on insects.
Glossary 383
ENZYME. An organic chemical product capable of
bringing about chemical changes, but without itself
undergoing any change, or entering into the final
product.
EXOSPORE. Outer covering of a spore.
F
FALCATE. Sickle shaped.
FLAGELLA. Whip-like appendage of protoplasm of bac-
teria and swarm spores.
FUNGUS. A plant of very low order. Its mycelium corre-
sponds to roots and reproduces by means of spores.
G
GLAUCUS. Sea green.
GONIDIA. Algz-like cells.
GUTTULATE. Drop-like.
H
HAUSTORIA. Special organs of a fungus used for attach-
ment or for obtaining food.
HosT. Any plant which nourishes a parasite.
HYALINE. ‘Translucent or colorless.
HYPERTROPHIED. Part of diseased plant abnormally
enlarged.
HYPH®. Thread-like vegetative part of a fungus.
I
INDURATED. Hardened.
INFECT. To cause disease.
INTERCELLULAR. Growing between the host cells.
INTRACELLULAR. Growing inside the host cells.
384 Glossary
L
LENTICEL. A special loose corky structure in plants
intended for the exchange of gases of the air and the
interior of the plant. :
LESIONS. A definite diseased area.
M
MACROCONIDIA. Large conidia.
MICROCONIDIA. Very small conidia.
MIDDLE LAMELLA. The connecting or cementing mem-
brane between any two cells of a plant. |
MYCELIUM. Vegetative threads or hyphe of a fungus.
mycoLoGy. The study of fungi.
O
OMNIvoROUS. Attacking a large variety of plants.
COGONIUM. Female sexual organ of fungi, containing
one or more oospheres.
OOSPHERE. Naked mass of protoplasm developing into
oospores after fertilization. -
OOSPORE. Fertilized oosphere. —
1
PAPILLATE. Having wing-like structures.
PARAPHYSES. Sterile filaments found in some fruiting
forms of fungi.
PARASITE. An organism living at the expense of another
(the host).
PATHOGENE. A disease-producing organism.
PEDICILLATE. Borne on a stalk.
Glossary 385
PERITHECIUM. A flask-shaped or globose sexual fruiting
. body containing asci.
PERITRICHIATE. Flagella all over the surface.
PIONNOTES. An effuse conidial stage containing a maxi-
mum of conidia and a minimum of aerial mycelium.
PLASMODIUM. A mass of naked protoplasm with numer-
ous nuclei and capable of amoeboid motion.
POLAR FLAGELLA. Flagella borne at the polar ends of an
organism.
PROTOPLASM. The living substance of any plant cell.
PSEUDOPIONNOTES. False pionnotes.
PSEUDOSTROMA. Falsestroma.
PUSTULE. A blister or pimple.
PYCNIDIA. Sac-shaped fruiting bodies of a fungus in
which the pycnospores or summer spores are formed.
PYCNOSPORES. Summer spores of certain fungi which
are formed in pycnidia.
S
SCLEROTIA. Compact masses of mycelium in a dormant
state. These help to carry the fungus over un-
favorable weather conditions.
SEPTUM. Any partition between two cells in the same
fungus filament.
SETH. Bristle-shaped bodies.
SOIL FLORA. Bacterial or fungus growth in a soil.
sorus. Heap of spores.
SPORANGIOPHORE. Stalk-bearing sporangium.
SPORANGIOSPORES. Spores formed in a sporangium.
SPORANGIUM. Free non-sexual bearing spore sac.
SPORES. Seed of bacteria or fungi.
STOMATA. Minute openings in the stems, leaves, or fruits
of plants which serve as a medium of exchange of
gases,
25
386 Glossary
stroma. A spore-bearing cushion composed of mycelium
and sometimes of host tissue. a,
SWARM SPORES. Spores possessed with the power of
motility. .
7.
TELEUTOSPORES (TELIOSPORES). Resting or winter spores
of certain rust fungi.
U
UREDOSPORES. Summer spores of certain rust fungi.
V
VESICULAR. Composed of vessels.
VIScID. Sticky.
Z
ZOOGLE%. Colony embedded in a gelatinous bed.
ZOOSPORANGIA. Sporangia which produce zoospores.
ZOOSPORE. A motile spore.
INDEX
A
Abbot, J..B., 30:
Acid sick soils, 25 et seq.
Acrostalagmus panax, 113.
Actinomyces, 6.
chromogenus, 317.
—— —— attacking beets, i20.
attacking radish, 209.
Alkali sick soils, 34 e¢ seq.
Allard, H. A., 84.
Allium cepa, 285.
Schoenoporasum, 284.
Alphano Humus Co., 20.
Alternaria brassice@, 196.
var. nigrescens, 223.
panax, 114.
Ammoniacal copper carbonate,
366.
Ammonification, 14.
Antheridium, 11.
Aphis gossypii, 233.
Apium graveolens, 355.
ATtAUT ae Cl, 7 Es.
Artichoke, Globe, diseases of,
139 et seq.
Leaf spot, 139.
Jerusalem, diseases of, 137
et seq.
Downy mildew, 138.
Leaf blotch, 138 et seq.
Rust, 138.
Ascochyta armoracie, 205.
hortorum, 302.
pisi, 277.
Asparagus (officinalis), 280.
diseases, 279 et seq.
Leopard spot, 280.
Rust, 280,
387
Asparagus, resistant to rust, 283.
—— rust, natural enemies, 283.
Atkinson, G., 43.
Available nitrogen, elaboration
of, 13.
B
Bacillus, 4.
Bacillus carotovorus, 192.
attacking onions, 285.
—— —— attacking salsify, 146.
—— fluorescens liquefaciens, 14.
putridus, 14.
lathyri, 201.
on cowpea, 270.
—— —— phytopthorus, 316.
melonts, 221.
mesentericus vulgatus, 14,23.
mycoides, 14, 23.
pestifer, 23.
proteus vulgaris, 14.
vamosus, 23.
subtilis, 23.
tracheiphillus, attaching cu-
cumber, 229.
Bacteria, distribution in soil, 6.
forms, 4.
influence of depth of cul-
tivation, 8.
number influenced by man-
ure, 9.
relationship to function of
soil, 5.
Bacterium teutlium, 118.
Balm diseases, 256.
Leaf spot, 256.
Rust, 256.
Barus, M. F., 265.
388
Bean diseases, 260 et seq.
Anthracnose, 263.
Blight, 260.
Damping off, 261.
Downy mildew, 261.
Powdery mildew, 262.
Rust, 262.
Sclerotinia rot, 263.
Stem anthracnose, 263.
Streak, 261.
Beattie, W. R., 293.
Beet diseases, 117 e¢ seq.
Crown gall, 118, 119.
Damping off and root rot,
122, 023.
Downy mildew, 123.
Drop, 124.
Leaf spot, 126, 127.
Leaf spot and heart rot,
125, 126.
Root knot, 129, 130.
Root rot, 128.
Root tumor, 121, 122.
Scab, 120-121.
Soft rot, 118.
Tuberculosis, 120.
Water core spots, 117.
White rust, 123.
Beneficial fungi, 376.
Bessey, E. A., 51.
Beta vulgaris, 117.
“Black leaf 40,” 368.
Bir SP K 220",
Blossom drop, 82, 83.
Bordeaux mixture, 364.
Branch, G..V., 226,
Brassica Japonica, 208.
oleracea, 186.
var. acephala, 207.
var. botrytis, 202.
rapa, 214.
Bremia lactuce, 141.
Brown, N. A., 140.
Cc
Cabbage diseases, 186 ef seq.
Black leg or foot rot, 195.
Black mold, 196.
Black rot, 190.
Index
Club root, 186.
Damping off, 193.
Downy mildew, 194.
Drop, 194.
Leaf spot, 196.
Root knot, 199.
Soft rot, 192.
White rust, 193.
Wilt or yellows, 197.
storage decays, 199 ef seq.
Cantaloupe, 225.
blight resistant, 225.
care in shipping, 225 et seq.
—— diseases, 219 et seq.
Anthracnose, 223.
Bacterial wilt, 219.
Cercospora leaf spot, 224.
Cladosporium mold, 224.
Downy mildew, 221.
Leaf blight, 223.
Mycospherella wilt, 222.
Phyllosticta leaf spot, 224.
Powdery mildew, 222.
Root knot, 225.
Soft rot, 221.
Southern blight, 225.
spraying, 232.
Capnodium, 238.
Carbon, transformation of, 13.
Carrot diseases, 354.
Root rot, 354.
Soft rot, 354.
Carum petroselinum, 357.
Catnip diseases, 257.
Leaf spot, 257.
Stem rot, 257.
Cauliflower diseases, 202 et seg.
Bacterial leaf spot, 202.
Ring spot, 204.
Causes of diseases in crops, 71
et Seq.
Celery diseases, 355 et seq.
Early blight, 357.
Late blight, 355.
Leaf spot, 355.
Rust, 355.
Soft rot, 355.
Cercospora apit, 357, 358.
armoraci@, 207.
—— canescens, 269.
Index
Cercospora capsisi, 304.
curullina, 243.
cruenta, 271.
cucurbit@, 224.
dolichi, 271.
hibisci, 295.
Chive diseases, 284.
Choanophora cucurbitarum, 235.
Chrysophylyctis endobioticuim,
319.
Citron diseases, 234.
Citrullus vulgaris, 234 et seq.
Cladosporium fulvum, 350.
macrocarpum, 134.
p., 284.
Minto) Gs; b.,- b22,) t24) 147,
215, 284, 323.
Coccus, 4.
Cochleaia armoracia, 204.
Colletoirichum atramentarium,
325, 326
caulicolum, 266.
Higginsianum, 214.
nigrum, 303.
—— phomoides, 348.
Combination sprays, 367.
Conidia, 12.
Conn J, He, 6:
Contact poisons, 363.
Convulvulus batatas, 15%.
Cooley, B. A., 368.
Corticium vagum, 128.
Cowpea diseases, 270 et seq.
Angular leaf spot, 271.
Powdery mildew, 271.
Rust 270.
Streak, 270.
Wilt or Yellows, 270.
Crop rotation, 272.
Cucumber diseases, 228 et seq.
Angular leaf spot, 229.
Anthracnose, 232.
Bacterial wilt, 229.
Damping off, 230.
Downy mildew, 230.
Mosaic, 228.
Powdery mildew, 230.
Root knot, 232.
spraying, 232.
Cucumis sativus, 228.
389
Cucumis melo, 219.
Cucurbita maxima, 234.
—— moschata, 234.
pepo, 234.
Cutworms, 52.
Cystopus candidus, attacking rad-
ish, 211.
on horseradish, 205.
ipomee-pandurane, 155.
—— portulacee, 299.
Cystospora batatas, 152.
D
Damping off, 42 ef seq.
Darluca filum, 284.
Daucus carota, 354.
Denitrification, 24.
Denitrified soils, 23.
Diabrotica vittata, 220.
Diaporthe battis, 157, 159.
Didlake, M., 20.
Didymella catarig, 257.
Diplodia herbarum, 258.
herbicola, 257.
tubericola, 165.
——, attacking watermel-
On 239...
Diseases of a mechanical nature,
72 et seq.
——of an unknown origin, 83
et seq.
due to bacteria or fungi,
86 ef seq.
Dodder, go, 91.
Doryland Ch., 8.
Drought injury, 78.
Duggar, B. M., 128, 298.
Durst,/C. EH. 233.
E
Edgerton, C. A., 264.
Edson, H. A., 209.
Eggplant diseases, 300 ef seq.
Anthracnose, 302.
Damping off, 301.
Fruit rot, 301.
Root knot, 303.
Southern blight, 303.
390
Eggplant diseases—Continued
Southern wilt, 301.
Stem anthracnose, 303.
Elliott, J. A., 154.
Enlows, E. M., 229.
Entyloma Ellisit, 133.
Erysiphe cichoracearum, 232.
galeopsidis, 258.
polygont, 216.
,on bean, 262.
, on cantaloupe, 222.
F
Family Agaricacez, 103 et seq.
Araliacez, 108 et seq.
—— Chenopodiacez, 116 et seq.
Composite, 137 et seg.
Convolvulacee, 151 et seq.
— Crucifere, 185 ef seq.
—— Cucurbitacez, 218 ef seq
Graminez, 250 ef seq.
Labiate, 255.
—— Liliacez, 279 et seq.
—— Malvacez, 295 et seg.
Portulacacez, 299.
Solanaceze, 300 ef seq.
Umbelliferze, 254 et seq.
Fence post treatment, 378.
Fertility of soil, 16, 17
Fisher, O. S., 31.
Fleet, W. V., 255.
Formaldehyde, treatment of soil,
53> 54-
Freiberg, G. W., 84.
Frost injury, 74, 75.
prediction, 76, 77.
protection, 77, 78.
Fuligo violacea, 152.
Fungicides, 363.
Fungi, structure and life history,
10. :
Fusarium batatatis, 47, 157, 170.
citrulli, 244.
conglutinans, 197.
cucurbite, 237.
eumartii, 330.
—— hyperoxysporum, 47 et seq.
lycopersict, 351.
niveum, 244.
we
Index
Fusarium orthoceras, 352.
oxysporum, 327, 352.
—— Poolensis, 244.
radicicola, 329.
trichothectotdes, 330.
tuberivorum, 331.
G
Garden pea, 275.
diseases, 273 et seq.
Pod spot, 276.
Root knot, 278.
Root rot, 278.
Septoria leaf spot, 278.
Stem blight, 273.
Thielavia root rot, 275.
Garman, H., 20.
Gilbert, W. W., 74.
Gilman, J. C., 198.
Ginseng, I10, III, 113.
diseases, 108 et seq.
Acrostalagmus wilt, 113, 114
Alternaria blight, 114.
Black rot, 110, III.
Bordeaux injury, 115.
Damping off, 108.
Downy mildew, 108, 109.
Fiber rot, 111, 112.
Leaf anthracnose, 113.
Papery leaf spot, 115.
Root knot, 115.
Stem anthracnose, 112.
White rot, IIo.
Gleosporium melongene, 302.
Glomerella piperata, 303.
Grossenbacher, J. G., 222.
H
Hail storm, 73, 74.
Halstead, B. D., 125.
Harding, H. A., 191.
Harris, B.S. 35.
Harter, L. L., 199, 301.
Hawkins, 321.
Headen, Wi. P16; 24:
Heald, F. D., 139, 266.
Healthy host and its require-
ments, 63 et seq.
Index
Healthy soil flora, nature and
function, 12.
Helianthus annuus, 148.
tuberosus, 137.
Heterodera radicicola, 48, 52, 332.
attacking cabbage,
199.
—— —— attacking beets, 129.
—— —— attacking lettuce, 146.
—— —— attacking sweet pota-
FO, 17S
Heterosporium variabile, 134.
Hibiscus esculentus, 295.
Hicks, G. A., 96.
Higgins, B. B., 214.
Hopkins, G. G., 31.
Horehound diseases, 258.
Leaf spot, 258.
Powdery mildew, 258.
Horseradish diseases, 204 et seq.
Leaf spot, 207.
Macrosporium black mold,
206.
Root rot, 205.
Shot hole, 206.
White mold, 206.
Humbert, J. G., 55.
Humphrey, J. E., 232.
I
Insecticides, 362.
Iron, changes of, 15.
Irrigation, methods of, 67 ef seq.
Isartopsts griseola, 269.
Istvanffi, G. De, 143.
ii
Jamieson, C. O., 331.
Johnson, J., 57, 276.
T., 320, 347-
Jones, L. R., 74.
K
Kale diseases, 207, 208.
Koch, Robert, 4.
391
L
Lactuca sativa, 140.
Lady beetles, 376.
Leeuwenhoek, Anton van, 4.
Lettuce diseases, 140 et seq.
Bacterial blight, 140.
Cercospora leaf spot, 145.
Downy mildew, 141.
Gray mold, 142.
Leaf spot, 144.
Lettuce drop, 143.
Root knot, 146.
Rosette, 146.
Shot hole, 145.
Levine, E., 347.
Lightning injury, 74, 75.
Lima bean diseases, 267 et seq.
Blight, 267.
Downy mildew, 267.
Leaf blotch, 269.
Leaf spot, 269.
Pod blight, 268.
Powdery mildew, 268.
Root rot, 269.
Rust, 268.
Texas root rot, 269.
Lutman, B. F., 318.
Lycopersicum esculentum, 339.
Lysiphlebus testaceipes, 375.
M
McClintock, J. A., 263.
McCulloch, L., 202.
McKay, M. B., 127.
Macrosporium herculeum,
257
—— parasiticum, 290.
porrt, 290.
—— solani, 325.
Sp., 304.
Malnutrition, 80 eé¢ seq.
Manns, T. F., 99, 195.
Marrubium vulgare, 258.
Marsonia perforans, 145.
Meier, F. C., 239.
Melanconium Tisdale, 349.
Melhus, T. E., 212, 323.
Meliotus alba, 20.
206,
392
Meliotus denticulata, 20.
lupulina, 20.
Melissa officinalis, 256.
Mentha virides, 258.
Merrill, L. A., 65.
Methods of control, 361.
Mint diseases, 258.
Monilochetes infuscans, 168.
More;.C.T.,
Morse, W. y. eat
Mosaic, 83 et seq.
Muck or peat soils, 34 ef seq.
Mushroom diseases, 103 et seq.
Bacterial spot, 103, 104.
The Mycogone disease, 103
et Seq.
Mustard diseases, 208.
Mycogone perniciosa, 104, 105.
' Mycospherella brassicola, 204.
citrulina, 22.
N
Nematospora lycopersict, 345.
Nepeta cataria, 257.
Niter-sick soils, 24.
Nitrification, 14.
Nitrobacter, 14.
Nitrogen fixation from air, 1S.
maintaining supply, 17
Nitrosococcus, 14.
Nitrosomonas, 14.
O
O’Gara,-P. J., ‘324.
Okra diseases, 295 et seq.
Leaf spot, 295.
Root knot, 298.
Root rot, 297.
Texas root rot, 297.
Wilt, 296.
Olpidium brassice, 193.
Onion diseases, 285 et seq.
Anthracnose, 289.
Black mold, 290.
Black neck, 290.
Blight, 286.
Bulb rot, 290.
Damping off, 286.
Index
Downy mildew, 286.
Pink root, 291.
Rust, 289.
Sclerotium rot or black
. neck, 290.
Smut, 288.
Soft rot, 285.
—— storage, 292 ef seq.
Oogonia, 43.
Oogonium, 11, 43.
Orton, W.A.4232) 2733.527-
Ozonium omnivorium attacking
okra, 297.
attacking sweet pota-
to, 175.
P
Pammel, L. H., 46, 123.
Parasitic fungi, Io.
soil Fusaria, 46, 47.
Parsley diseases, 357.
Drop, 357-
Late blight, 357.
Parsnip diseases, 357.
Early blight, 357.
Root rot, 357.
Pastinaca satiwa, 357.
Penicillium expansum, 11.
Pepper diseases, 303 et seq.
Anthracnose, 303.
Black anthracnose, 303.
Fruit rot, 304.
Leaf spot, 304.
Southern blight, 305.
Peppermint diseases, 258.
Perithecium, 12.
Peronospora effusa, 131, 132.
parasitica attacking cab-
bage, 194.
Schachtit, 123.
schleideni, 286.
Pestalozzia funerea attacking gin-
seng, 113.
Phaseolus vulgaris, 260.
Phoma bete, 125.
destructiva, 346.
napobrassice, 215.
———— oleracea, 195.
solani, 324.
Index
Phoma subcircinata, 268.
Phomosts vexans, 301.
Phosphates, changes of, 15.
Phyllosticta apit, 355.
batatas, 164.
chenopodit, 133, 134.
cucurbitacearum, 224.
Physiological diseases, 80 e¢ seq.
Phythium de Baryanum, 42, 44,
attacking beet, 122.
Phytophthora cactorum, 108.
infestans, late blight of
Irish potato, 322.
late blight of tomato,
—_—
343- f
—— phaseoli, 267.
terrestrid, 344.
Pisum sativum, 273.
Plasmopora Halstediz, 138, 148.
Plenodomus destruens, 159.
Points to remember, 366.
Pool Venus, 127.
Poor seed, 92, 97.
Potassium, changes of, 15.
sulphide of, 369.
Potato diseases, 306 et seq.
Anthracnose, 324.
Arsenical injury, 313.
Black heart, 311.
Black leg, 316.
Black rot or jelly end rot,
329.
Black wart, 319.
Common scab, 317.
Curly dwarf, 309.
Early blight, 322.
Fusarium wilt, 327.
Hollow heart, 312.
Internal brown spotting,
310.
Late blight, 322.
Leaf roll, 308.
Melters or leak, 321.
Mosaic, 312.
Net necrosis, 311.
Phoma rot, 324.
Powdery dry rot, 330.
Powdery scab, 314.
Pox or pit, 313:
ww
\O
Ge
Root knot, 332.
Rosette, 331.
Silver scurf, 326.
Southern blight, 332.
Southern wilt, 317.
Spindling sprout, 310.
Stem end rot, 329.
Tip burn, 312.
——- diseases, field control, 335.
—— storage rots control, 333.
Predacious insects, beneficial,
375-
Pseudomonas beticola, 120.
—— campestris, 190, I91, 205.
—— —— attacking radish, 208.
attacking turnip, 214.
—— fluorescens, 103, 104.
—— lachrymans, 229.
—— maculicola, 202, 203.
pist, 273.
—— radicicola, 18 et seq,
solanacearum, attacking to-
mato, 342.
Stewarti, 251.
—— tumefaciens,attacking beets,
118.
viridilividum, 140.
Pseudoperonospora cubensis, 230.
Puccinia alli, 289.
asparagt, 280.
—— bullata, 355.
helianthi, 149.
attacking Jerusalem
artichoke, 138.
tragopogont, 148.
Purslane diseases, 299.
Pycnidium, 12.
R
Radish diseases, 208 et seq.
Black rot, 208.
Club root, 208.
Damping off, 209.
Downy mildew, 211.
Root knot, 214.
Root rot, 214.
Scab, 209.
White rust, 211.
Rainstorms, 73.
394
Ramularia armoracie, 206.
cynar@, 138.
Rand, F. V., 229.
Rankin, W. H., 110.
Raphanus sativus, 208,
Readhimer, J. E., 31.
Reid Hi L:, 134, 138-
Resin, 370.
Resistant varieties, 373.
Rheosporangium apianiderma-
tum, 209.
Rhizoctonia solant, 44.
Rhizopus nigricans, 156, 158.
attacking squash, 236.
the cause of leak, 321.
Roasting or pan firing, 56.
Rogers, S. S., 356.
Root knot, 48 et seq.
Root rot, caused by Rhizoctonia
solant, 45, 46.
Rosenbaum, J., 109, I10, 314.
S
Sackett, W. G., 24.
Salsify diseases, 146 ef seg.
Rust, 148.
Soft rot, 146.
Southern blight, 148.
White rust, 147.
Sal soda, 370.
Sanitary environment, 69, 70.
Sarcina lutea, 14.
Schneider, A., 345.
Schrenk, H. von, 203.
Sclerotinia libertiana, 45.
attacking bean, 263.
—— —— attacking beet, 124.
—— —— attacking cabbage,
attacking ginseng, 110.
panacis, 110.
Sclerotium bataticola, 157, 173,
1 Sa
cepivorum, 290.
—— Rolfsit, 44. _
attacking cantaloupes,
225.
attacking peppers,
Index
Sclerotium Rolfsti,
sweet potatoes, 174. -
—— —— attacking watermelon,
247.
Seed, age of, 92.
cultural conditions, 92, 93.
fertilizer effect, 95, 97.
storage conditions, 94.
testing, 95.
treatment against insects,
attacking
— treatment with formalde-
hyde, 99.
weight and color, 93, 94.
Selby, (Al D2 ee er.
Septoria bataiicola, 165.
consimilis, 144.
—— lactuce, 144.
lycopersici, 347.
meliss@, 256.
—— nepele@, 257.
—— pist, 278.
Shamel, A. D., 54.
Sherbakoff, C. D., 331, 344.
Sick soil, treatment, 53.
Sirrine, F. A., 282.
Smith, E. F., 119, 190, 251.
—— E. W., 230.
Smoke injury, 78 et seq.
Soft rot, 236.
Soil flora, action on mineral sub-
stances, I4.
Solonum tuberosum, 306.
Spearmint diseases, 258.
Spherella pinodes, 276.
Spheronema fimbriatum, 160,
173:
Spinach diseases, 130 ef seq.
Anthracnose, 132.
Black mold, 134.
Downy mildew, 131, 132.
Leaf spot, 134, 136.
Malnutrition, 130, 131.
Phyllosticta leaf blight, 133,
134.
White smut, 133.
Spinacia oleracea, 130.
Spondylocladium atrovirens, 324,
326.
Index
Spraying, 361.
- machines, 370.
principles involved, 370.
Squash diseases, 234 et seq.
Anthracnose, 237.
Bacterial wilt, 234.
Fruit rot, 235.
Leaf spot, 237.
Powdery mildew, 237.
Root knot, 238.
Root rot, 238.
Soft rot, 236.
Wilt or yellows, 237.
Steaming sick soil, 54.
Stevenson, J. A., 146.
Stewart, F. C., 128, 285.
Be p50.
Stickers, 370.
Stock solutions, 364.
Stomach poisons, 362.
Stone, G. E., 93.
Rea 277
Subirrigation, 67, 68.
Sulphur, 367.
Sunflower diseases, 148.
Downy mildew, 148.
Rust, 149.
Surface or spray irrigation, 68,
69.
Sweet potato diseases, 151 ef seg.
Black rot, 160.
Charcoal rot, 173.
Cottony rot, 174.
Dry rot, 159.
Foot rot, 159.
Java black rot, 165.
Phyllosticta leaf blight, 164.
Ring rot, 158.
Root knot, 176.
Septoria leaf spot, 165.
Slime mold, 152.
Soft rot, 156.
Soil rot, 152.
Soil stain or scurf, 168.
Texas root rot, 175.
Trichoderma rot, 167.
Vine wilt or yellows, 170.
White rust, 155.
methods of control,
176 et seq.
395
T
Taubenhaus, J. J., 160 et seq.
Pemplew|yCs 9:
Thick sowing, effect on damping
Oso /-
Thtelavia basicola attacking gar-
den pea, 275.
attacking ginseng, 111.
attacking horseradish,
205.
Piusley.}) Ds 37:
Tolaas,, A. S., 103.
Tomato diseases, 339 ef seq.
Anthracnose, 348.
Blossom end rot, 340.
Buckeye rot, 344.
Damping off, 343.
Fruit rot, 346.
Hollow stem, 339.
Late blight, 343.
Leaf spot, 347.
Melanconium rot, 349.
Mosaic, 341.
Rhizoctonia fruit rot, 353.
Southern wilt, 342.
Sunburn, 341.
Yeast rot, 345.
Yellow blight, 352.
Tragopogon porrifolius, 146.
Trichoderma kéningi, 167.
lignorum, 167.
Tubercularia persicina, 284.
Turnip diseases, 214 et seq.
Anthracnose, 214.
Black rot, 214.
Club root, 214.
Macrosporium leaf spot, 217.
Phoma rot, 215.
Powdery mildew, 216.
iG.
Uredinales, ro.
Urocystis cepule, 288.
Uromyces appendiculatus, 262.
Urophlyctis leproides, 121.
396
V
Veihmeyer, F. J., 105.
Vermicularia circinans, 289.
dematium, 112.
Vertecillium albo-atrum, 326.
W
Ward, M., 43.
Water, need of plants, 64, 67.
Watermelon diseases, 238 et seq.
Anthracnose, 240.
Bacterial wilt, 238.
Blossom end rot, 247.
Cercospora leaf spot, 243.
Downy mildew, 238.
Fruit rot, 247.
Index
Honey dew or sooty mol
238.
Malnutrition, 238.
Mycospherella wilt, 239.
Powdery mildew, 238. z
Root knot, 246. :
Stem end rot, 239.
Vine wilt or yellows, 244.
Whetzel, H. H., 110, 287.9%
White grubs, 52.
Whitney, M., 64.
Widtsoe, J. A., 65.
Wind storms, 72, 73.
Wire worms, 52.
Wolf, F. A., 139, 235.
Wollenweber, H. W., 331.
Z
Zea mays, 250.
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