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Bulletin 457

May, 1942

Tobacco Substation at Windsor
Report for 1941

P. J. Anderson and T. E. Swanback

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Bulletin 457

May, 1942

Tobacco Substation at Windsor
Report for 1941

P. J. Anderson and T. R. Swanback

(ftonnettknt

JVari cultural ^Experiment Station

£sTem fjaiint

CONTENTS

Page

Introduction • • • • 227

The Relative Crop-Froducing Capacity of Urea and Cottonseed Meai 229

The Effect of Some Sources of Phosphorus on Cigar Leae Tobacco 234

Chemical Analyses • • 237

The Effect of Source on Magnesium Absorption by Tobacco 239

Leaf Content of Magnesium and Calcium 241

Residual Effect of Stable Manure 242

Further Experiments on Starter Solutions • 243

Use of Carbon Black to Activate Growth Early in the Season 244

Further 1 information on Irrigation of Tobacco 246

lumartth as a substitute for glass in the seed bed sash 247

Tobacco Diseases in 1941 248

Some Experiments on the Control of Downy Mildew 248

Exit Wildfire 250

Delayed Frost Injury to Transplants in June 2?^

Mosak or Calico Disease of Tobacco ■ 253

i ! i 5TIGATIONS DURING 194] 260

Flea Beetli and Thrips Experiment 260

Control Experiments on Open Field Tobacco 261

Wireworm < Control Experiments 2*<2

In 'ii Abundance During 1941 _\,)

TOBACCO SUBSTATION AT WINDSOR

Report for 1941
P. J. Anderson and T. R. Swanback

The Twentieth Annual Report of the Tobacco Substation at Wind-
sor is presented herewith. It is not the object of these annual
reports to describe in detail all of the work done during the year on
each of many tobacco research projects. Most problems require a
continuation through several years before a final answer can be given.
In general, it seems best to wait until the conclusion of a project
before discussing it in the annual report. On some, however, a pro-
gress report is considered necessary. A case in point is the study on
phosphorus tests described in this bulletin. On account of world
conditions, growers can no longer obtain certain phosphates they have
been accustomed to use, and other kinds must be substituted. It may
help the grower in choosing a substitute to present here the results
of the first two years of a test on various phosphatic materials, even
though we have not yet drawn final conclusions.

The growing season of 1941 was on the whole unusually favorable
for the production of good tobacco in the Valley. A few local hail
and wind storms caused considerable damage but these were confined
to small areas. Rainfall was favorable in distribution and amount,
as indicated in Table 1, and kept the crop growing steadily. There
were no serious leaching rains. The curing season was quite dry,
with the result that there was practically no pole rot in this year's
crop. Most of the tobacco diseases were at a low ebb and there were
no serious insect infestations.

Table 1. Distribution of Rainfall in Inches at the Tobacco Substation,
Windsor, 1941.

May

June

July

August

TEN-DAY PERIODS

1-10

11-20

21-31

1-10

11-20

21-30

1-10

11-20

21-31

1-10

11-20

21-31

2.38

.45

.62

3.10

.52

2.12

.45

3.07

.76

1.06

.64

3.45

4.42

BY MONTHS

5.64

2.46

3.35

AVERAGE
3.79

FOR PRECEDING

19 YEARS
3.74

4.25

228

Connecticut Experiment Station

Butt< tin 47>,

Of the various forms of direct service offered by the Station,
growers take most advantage of the free soil testing service. They
have learned to take their own samples. They bring these into the
laboratory and. after tests have been made for acidity, nitrogen, pot-
ash, phosphorus, calcium, magnesium and sometimes other elements,
growers often sit down with the Station agronomist and figure out the
best fertilizer formulas for their fields, on the basis of the soil tests.
In 1041 over 4,000 samples of soil were brought in and tested before
the ground became frozen and ended this work.

A sum of $1,500 was appropriated for material to build a three-
car brick garage. Plans were drawn, contracts let and materials de-
livered, but work was interrupted when the ground froze in Decem-
ber. This much needed addition to the plant will be finished in
the spring.

Table 2 shows the acreage and production of each of the three
types of Connecticut Valley tobacco for 1941 and a comparison with
1940 and an average of the previous ten years.1 This table shows a
small increase in acreage of Broadleaf, a smaller decrease in acreage
of Havana Seed and a small increase in Shade. Both Shade and
Havana Seed are well above the ten-year average. Only Havana
Seed shows a large increase in poundage over the ten-year average.

Table 2. Acreage and Production of Connecticut Valley Types in 1940 and
1941 Compared with a Ten-year Average.

Acres

Production in pounds

Types

1941

1940

1930-39

1941

1940

1930-39

Broadleaf

Havana Seed
Shade

8,300
8,100
6,800

8,000

8,200

0,400

8,680
7,690
6,170

13,284.000

14.166,000

(i.083,000

33,533.000

12,326,000

14,111,000

5,515.000

31,952,000

13.373,000

11. (.58.000

6.025,000

Total

23,200

22,600

22,540

31,056.000

The impact of the world war on our tobacco industry was already
being fell in L941 and will surely be greater in 104:4. First of all,
labor became scarce and high priced because of the location of defense
industries in the Valley. These firms paid wages the tobacco farmer
could not hope to meet.

Prices of materials, machinery, shade cloth, fertilizers, etc. have

been climbing. Certain kinds of fertilizer materials which the to-
bacco grower especially preferred have about gone oil' the market.
Precipitated bone, the favorite source of phosphorus, cannot be ob-
tained. Other forms of bone are also scarce. A shortage of domestic
sources of potash was anticipated hut has not developed. There
seems to he enougb domestic sulfate of potash and cottonhlll] ashes

in take 'arc of the potash requirements. Uramon, winch has come to
\>i- an im port a hi source of nitrogen in tobacco mixtures, can no longer
he obtained because the DuPonl Company, the sole manufacturer of

1 from release of New England Crop Reporting Service December 28, L941.

Tobacco Substation Report for 194-1 229

this material, has been obliged to turn so much of its chemical pro-
ducing capacity to war chemicals. The effect of dislocations of
freight and ocean transport on the other materials cannot be pre-
dicted at this time.

Since practically all Connecticut-grown tobacco is used domesti-
cally, the loss of foreign markets has no effect on it. The cutting off
of Sumatra by war in the Pacific, however, may have a profound
effect on our Shade industry. From one-third to one-half of the
cigars produced in America are wrapped with Sumatra Leaf. There
is now a large supply in this country but, if the war should continue
to isolate Sumatra until this supply runs out, other sources of cigar
wrappers- must be found, and the logical substitute is Connecticut
Valley Shade. If manufacturers should all turn to Shade the acre-
age could be almost doubled.

Detailed or summary reports on some of the projects under way
at the Substation are presented in the following pages.

THE RELATIVE CROP-PRODUCING CAPACITY OF UREA
AND COTTONSEED MEAL

The crop-producing capacity of any nitrogenous fertilizer is re-
lated to the nitrate concentration which it can develop and maintain
in the soil during a relatively short period, from mid-June until
early August. Very little nitrate is needed by the tobacco plants
previous to this time and any that is supplied after this period —
when the crop is already mature or harvested — is obviously wasted.
Measurements of the concentration of nitrates in the soils to which
such materials have been applied should, therefore, give the first in-
dication of crop-producing efficienc}7. Such measurements were made
at weekly intervals for four years (1932-35) at the Substation on
tobacco plots treated with single nitrogen carriers. The results were
published in Conn. Sta. Bui. 386, pp. 552-574. Comparing the cot-
tonseed meal figures with those for urea (Table 13 of that report)
we find that the average concentration of nitrate in the soil between
June 18 and August 13 was 37 pounds per acre for cottonseed meal
and 58 pounds for urea, i. e., cottonseed meal was much less effective
than urea in its nitrate-producing capacity during these critical few
weeks.

That more nitrate nitrogen is liberated from urea than from
cottonseed meal and that the crop is able to utilize more of it is also
indicated by lysimeter experiments which have been carried on here
since 1929. In the lysimeter tests all nitrate nitrogen which is re-
moved from the soil, either by leaching or by the growing crop dur-
ing the year, is accurately measured.

Results of these 1940-41 lysimeter studies in nitrogen removal
by the crop and by leachate are given for urea and cottonseed meal

•_':;<>

Connecticut Experiment Station

Bulletin 457

in Table 3.1 This table shows that, starting with the same amount
of nitrogen supplied in the fertilizer, a greater percentage was always
recovered in the crop and that the total recovery (crop and leaching)
was also always higher for urea.

In another series of lysimeter tests, 200 pounds per acre of ni-
trogen, in urea and cottonseed meal, were added to the soil annually
for nine years. This was cropped to tobacco. The average annual

Table 3. Removal of Nitrate Nitrogen by Crop and by Leaching in 12
Months, 1940-41. Comparison of Urea and Cottonseed Meal in
Lysimeters.

Pounds of nitrogen

Nitrogen carrier

Pounds of nitrogen recovered

added in

fertilizer

In
crop

Leached as
nitrate

Total

None

120

Urea
Cottonseed meal

91
65

58
68

149
133

160

Urea
Cottonseed meal

100

77
73

177
150

200

Urea
Cottonseed meal

130

90
84

220
169

removal of nitrogen (nitrate nitrogen in the leachate and total nitro-
gen in the plants) was 165 pounds for urea, 145 pounds for cotton-
seed meal and 47 pounds where no nitrogen was applied as fertilizer.
We may assume that the 98 pounds (145 minus 47) of the nitrogen
derived from cottonseed meal was sufficient to raise a normal crop;
Since 2<)(i pounds of nitrogen as urea liberated 118 pounds in excess
of soil production of available nitrogen, then 166 pounds of nitrogen
added in this material could supply the required 98 pounds. Thus,
in this test, urea was about 20 percent more efficient than cottonseed
meal in providing nitrates for crop use.

On the held plots mentioned in the first paragraph in this section,
the crop fertilized with urea was always larger than that on the
cottonseed meal plots, the latest published report (Bui. 386, p. 546,
of this Station) showing an average annual increase of 100 pounds
of cured tobacco to the acre for urea during the six preceding years.

The tobacco on the urea plots, how -ever, was inclined to be too dark

and heavy for best quality. Since this objectionable characteristic
often has been observed on plots which were too heavily fertilized

with nitrogen from any source, it was natural t<> conclude that the

same cause was operating here ami (hat the ration of nitrates fur-
in led by urea was loo great for obtaining the best quality leaves.

Data on the I; Imeter experiments furnished by M. B\ Morgan of the Soils De«
partment.

Tobacco Substation Report for 191^1

231

Assuming that this conclusion was correct, it seemed desirable
to determine by field tests the relative efficiency of the two materials.
If 200 pounds of nitrogen to the acre in cottonseed meal be regarded
as the standard amount for growing a normal crop of tobacco, how
much nitrogen in urea should be used to produce the same results?

To answer this question a series of 18 one-thirtieth acre plots
was laid out in 1937, with six different treatments in triplicate. The
only differences in the fertilizer applications to these plots were in
the quantity and source of nitrogen, all other fertilizer ingredients
being kept constant. The various nitrogen treatments were:

150 pounds N in urea

150 pounds N in cottonseed meal

175 pounds N in urea

175 pounds N in cottonseed meal

200 pounds N in urea

200 pounds N in cottonseed meal

All plots received the same cultural treatment and were grown
and harvested in the customary way for Havana Seed tobacco. The
cured leaves were graded and weighed in the Station warehouse and
the grades computed to a single figure (grade index1) from the

Table 4. Efficiency of Urea Compared with Cottonseed Meal. Four Years'
Summary of Yields and Grading.

Material

Lbs. N
per
acre

Acre yielc

Grade index

1937

1706
2045
2073
2095
2152
2077
1957
2273
2162
1849
2033
1790
2004
2091
1916
2355
2227
1988

1939
1803
1916
1940
1940
2058
2092

1940

1506
1532
1444
1495
1490
1419

1941

Av.

1937

1939

1940

1941

.405
.407
.397

Av.

Urea

150

1894
2206
2038

1843

.302
.367
.366

.373
.393
.392

.294
.349
.336

.365

Urea

175

2116
2134
2014

1924

.396
.380
.369

.391
.379
.397
.398
.373
.384
.376
.388
.347
.358
.383
.361

.349
.283
.291
.345
.355
.341
.359
.380
.355
.370
.368
.328
.347
.321
.306

.429
.377
.381

.369

Urea

200

2005
2046
2000
1875
1872
1831

1830
1937
1823

1500
1688
1523
1510
1605
1430
1514
1581
1515
1504
1582
1495

2315
2346
2123
1916
2058
1864

1995

.335
■ .380
.403
.326
.326
.342

.366
.345
.345
.384
.380
.360

.448
.396
.395
.364
.385
.319

.380

C. S. M.

150

1803

.355

C. S. M.

175

1857
2147
1886

1842

.377
.385
.340
.418
.408
.382

.360

C. S. M.

200

1924
1891
1770

2250
2178
1947

1926

.368
.391
.349

.368

1 Grade index is a figure which represents the relative value of a lot of tobacco
computed on the percentage weight of each grade of leaves in the lot and the relative
values of these grades. Assuming that the light wrapper is the perfect leaf of Havana
Seed tobacco, we assign to it a value of 100. The other grades are assigned values
of the same proportion of 100 as their market value was to the price of the light
wrapper when this system was established. Thus medium wrappers have a value of
60; long seconds (19 inches or more) are 60; short seconds (15 and 17 inches) are
30 ; long darks are 30 ; dark stemming (short darks of 15 and. 17 inches) are 20 ;
fillers and brokes are 10. It is true that the values of these grades have fluctuated
considerably during the 15 years that we have used this system of comparing lots of
tobacco but, in order to be able to average results over a period of years, it seems
advisable to retain the same system for the present. To obtain the grade index
figure the percentage of each grade in a lot of tobacco is multiplied by the relative
values noted above and the products are added.

232

Connect/cut E.r/>< r'nnent Station

Bulletin 457

weisrhts and relative values of each grade. The results are presented
in Table 4 for the years 1937, 1939, 1940 and 1941. The crop of 1938
was omitted from the calculations because the extreme vreather con-
ditions of that year resulted in such poor quality that for the most
part it was not worth sorting.

From the averages (bold face type) in this table the following
observations may be made:

1. Each increase in quantity of nitrogen in the fertilizer, whether
in urea or in cottonseed meal, produced an increase in yield.

2. Each increase in fertilizer nitrogen, regardless of source, im-
proved the grade index.

3. When the quantity of nitrogen was the same, both the yield
and index were always higher for urea.

CONCENTRATION Of NITRATES
IN THE SOIL Of PLOTS
rCDTILIZCO WITH COTTONSIID
UEAL AND UREA

I i I i iDATE PF TF-rTING !HE SP,L i i i i i

jjj, , JUNE I JUNC 7 JUNCH JUNE 21 JUNE 2» JUUT I JULY I) JULY II JULY It AUG J AUO 0 AUO IC AUC J4 SCUT

Figure 1. Concentration of nitrate in soils of urea and cottonseed meal plots
during season of 1937.

I. Willi 17.) pounds of nitrogen in urea practically the same
yield and grade index were obtained as with 200 pounds of nitrogen
in cottonseed meal.

5. Winn the urea nitrogen was reduced to L50 pounds, however,
the average yield was considerably below thai of 200 pounds in cot-
tonseed meal. The errade index was also somewhal lower. In (wo

Tobacco Substation Report for 194-1 233

out of the four years, however, 150 pounds in urea was as good as
200 in cottonseed meal.

The results from, four years of this trial indicate, therefore, that
urea nitrogen is at least 14 percent more efficient than cottonseed
meal nitrogen in its crop-producing capacity.

During one year of this field test (1937) the nitrate concentration
in the soil was determined at weekly intervals. The average of all
urea plots, contrasted with the cottonseed meal plots, is graphically
presented in Figure 1, where it will be seen that urea consistently
accumulated more nitrate than did cottonseed meal. The average
concentration of nitrates in all urea plots, from June 14 to August
16, was 73.5 pounds of nitrogen per acre, contrasted with 41.6 for
the cottonseed meal plots. This suggests that the better yield on
the urea plots was due to the greater supply of nitrates available in
the soil during the critical period. It will be observed, however, that
the difference in nitrate concentration is greater than the percentage
increase in crop production, showing that the crop return is not
exactly proportional to the quantity of nitrates in the soil. This
may be due to the presence of other growth materials in cottonseed
meal or to the fact that the yields here are too close to the upper
limit of possible crop response to increased fertilizer; i. e., the law
of diminishing returns is operating. A more correct conclusion may
be drawn by comparing the "175 pound urea" plots with the "200
pound cottonseed meal" plots. These two gave nearly the same crop
response, as already noted. The average concentration of the former
during the summer was 53 pounds of nitrate-nitrogen per acre while
the latter was 48 pounds. This makes a difference of 5 pounds, which
is probably too small to be of significance in these field tests.

Comparative Grading. An important question to the handler
of tobacco is : what effect does the substitution of urea for cottonseed
meal have on the percentage of grades when the leaves are sorted?

The sorting records for the crop of 1941 on these plots are shown
in Table 5.

This year is selected because it was the final year of the test
and should, therefore, show the maximum results of any cumulative
effects from continuous use of each fertilizer. Moreover, it was a
favorable growing season and resulted in the most regular crop of
the series. The data presented in this table show that, contrary to
our previous impression, urea did not increase the percentage of
dark grades nor decrease the percentage of the better light grades.
For the same quantity of fertilizer nitrogen, therefore, the grade
index was uniformly higher for urea. No burn tests were made this
year because many previous trials at this Station (see particularly
Bui. 299, p. 172) have demonstrated that the fire-holding capacity
is not affected by the use of urea. Divergent opinions have been ex-

234

Connecticut Experiment Station

Bulletin 451

pressed by buyers, packers and manufacturers as to the effect of urea
on the more intangible qualities such as taste, aroma, finish and the
like. Since there is no known method of measuring these factors of
quality, and. moreover, opinion is so diversified, this question does
not appear close to solution in the near future.

Table 5. Yield and Grading Records of Urea Efficiency Compared with
Cottonseed Meal Plots. Crop of 1941.

Material *

Lbs. N
per
acre

Plot
no.

Yield, lbs.
per acre

Percentage of grades

Grade
index

Crop

Plot
1894
2206
2038
2116
2134
2014
2315
2346
2123
1916
2058
1864

Av.

M
2
2
2

2
1
1

1
2
1

1
1

2
3

4
2

39
34
37

37
31
34

43
36
38
32
34
26

33
31

35
36
35

ss
2
3
3
2
7
4

2
2
3
4
4
2

4
3

3
3

38
42
37

37
46
43

39
37
41
39
40
40
37
43
50
41
41
38

2
1
4
2
2
3

1
1
3
4
4
5
6
3
4

1
3
6

8
12

9
11

11
10
12
12
10
13

B
6
6
3

5
1
4
2

ll
2

5
15

4
4

5
3
4

Plot

Av.

index

Urea

150

X70

N70-1

N70-2

2046

2
4
2

1
1

3
1

.405
.407
.397
.429
.377
.381

.448
.396
.395
.364
.385
.319
.377
.385
.340
.418
.408
.382

.403

824.54

Urea

175

N71
N71-1

N71-2

K72

N72-1

N72-2

X73

N73-1

N73-2

N74

N74-1

N74-2

2088

.396 826.85

Urea

200

2261

.413

933.79

C. S. M.

150

1946

2
2

4
3
1

.356

.367

692.78

C. S. M.

175

1857
2147
1886

1963

720.42

C. S. M.

200

N75

N75-1

N75-2

2250
2178
1947

2125

.403

856.38

1 Relative Crop Values.

200 Urea = 109.0

175 Urea = 96.6

150 Urea = 96.3

200 C. S. M. = 100.0
175 C. S. M. = S4.1
150 C. S. M. = 80.9

THE EFFECT OF SOME SOURCES OF PHOSPHORUS ON
CIGAR LEAF TOBACCO.

T. K. Swanback, M. F. Morgan and P. J. Anderson

In the fertilization of tobacco in the Connecticut Valley growers
have been accustomed to use hone phosphates in one form or another.
Precipitated bone is probably the most commonly used material.
Earlier investigations by Jenkins in 1914 (Conn. Sta. Bui. 180:28-30)

and later by Nelson and Anderson (Tobacco Sta. Bui. SllT-lM)

-liowed favorable results with precipitated bone. The greater portion
of this materia] is usually imported from Belgium. Due to present

war conditions this source of supply is suspended. Even a second

choice of hone phosphates, such as raw hone and steamed bone, soon
"iay lo 'I he available in sufficient quantities to meel the demand.

In anticipation of such shortage of hone phosphates, an experi-
ment on held plots ill the Windsor Substation was begun with the
object of finding whether other phosphates could he substituted.

Tobacco Substation Report for 194-1 235

Included in the materials, in addition to precipitated bone and
steamed bone, were concentrated superphosphate (triple superphos-
phate), calcium metaphosphate, potassium metaphosphate and potas-
sium calcium metaphosphate. These were furnished by the Tennessee
Valley Authority. The last mentioned material was added to the
tests in 1941, while the others were included in the experiment when
it was begun in 1940.

The field allotted to the experiment had been used for vegetable
crops for many years previous to 1940 and possessed normal fertility.
Therefore, it was not anticipated that there would be symptoms of
phosphorus deficiency on plots included in the test, even where the
fertilizer contained no special carrier of phosphorus.

The various phosphatic materials, each furnishing 116 pounds
P2O per acre, were added to one common fertilizer formula that in-
cluded uramon, soybean oil meal and nitrate of soda as carriers of
nitrogen and potash in the form of sulfate of potash. These mate-
rials were selected because of very low content or almost entire lack
of P*Os. Lime, magnesium sulfate (Emjeo) and landplaster were
also included for the purpose of establishing acid-basic balance and
distributing an exact and uniform amount of plant nutrients among
the treatments. All tests were carried out in quadruplicate (one-
fortieth acre) plots, except the potassium calcium metaphosphate.
For tests on the latter material, the size of the field permitted in-
clusion of only two plots.

The summer of 1941 was a favorable growing season and uni-
form growth was observed on the entire field. In mid-season, how-
ever, it was noticed that tobacco on the calcium metaphosphate plots
had a more luxuriant spread and was taller than that under other
treatments.

The following general remarks were made at the time of sorting.

No P-carrier : short, dark, coarse, not veiny.
Precipitated bone : good to very good quality, not veiny.
Triple superphosphate : good, veiny, slightly reddish.
Steamed bone : good, but a little heavy, slightly veiny.
Ca-metaphosphate : ■ very good quality, slightly veiny.
K-metaphosphate : very good quality, slightly veiny.
K, Ca-metaphosphate : very good but short, not veiny.

The yield and grading records will be found in Table 6.

In examining the yield data it is apparent that, in the second
year of the experiment, there was no difficulty in obtaining heavy
yields on this particular test field, even with no special phosphorus
carrier.

Calcium metaphosphate and triple superphosphate produced
about 7 percent higher yields than the check ; precipitated bone about
5 percent higher, while steamed bone equalled the check. However,

236

Connecticut Experiment Station

Bulletin 457

none of these deviations from the yields of the check plots might be
considered significant.

On the other hand, potassium metaphosphate and potassium cal-
cium metaphosphate produced an average of 15 percent lower yields
than the control plots. It is of interest to keep in mind that potas-
sium is the carrier of phosphorus in both these materials. Potas-
sium calcium metaphosphate contains only about 4 percent CaO
and over 35 percent KX); that is, the same as for potassium meta-
phosphate.

Table 6. Yield akd Grading Records of Phosphorus Plots. Crop of 1941.

Yielc

lbs.

Treatment

Plot no.

per

acre

Percentage of g

ades

Grade index

Plot

Av.

LS
38

SS | LD

DS
1

B
1

Plot
.403

Av.

Xo phosphorus

Pll

2503

carrier

Pll-1

2300

.391

Pll-2

2040

2352

.393

.406

Pll-3

2564

3
4

4
3

40
31

3
3

41
48

7
9

1
1

.436
.409

Precipitated

P12

2490

bone

P12-1

2599

.416

PI 2-2

2657

2457

.442

.409

P12-3

2082

47
43

2
1

11
8

3
2

.369
.412

Triple super-

P13

2403

phosphate

P13-1

2602

.413

P13-2

2694

2517

.409

.412

PI 3-3
P14 "

2369

42
36

43
46

1
1

7
9

1
1

.415
.414

Steamed bone

2511

P14-1

2183

.421

P14-2

2335

2344

.420

.418

PI 4-3

2348

2
5

2
3

40
38

40
42

3
2

.415
439

Calcium

P15

2472

metaphosphate

P15-1

2556

.435

P15-2

2596

2519

.436

.446

PI 5-3

2450

.474

Potassium

P16

1984

.421

metaphosphate

P16-1

1809

.339

P 16-2

2350

2071

.443

.396

PI 6-3

2141

.380

Potassium Ca-

P17

1944

.435

metaphosphate

P17-1

1883

1914

.412

.424

Although reasonable yields are of importance in crop production
wuli respect l<> leaf tobacco, quality is still more important. Of the
materials tested, only the calcium metaphosphate produced tobacco
decidedly superior in grade to that of t\\a control plots (average

grade index .406, as compared with .446). In addition, it is note-
worthy that calcium metaphosphate produced about, VI percent less
"darks"" than the check.

The other sources Of phosphorus produced tobacco of somewhat.

higher grading than the control (two oui of four plots of potassium
metaphosphate reached higher indexes than the cheek). The varia-

Tobacco Substation Report for 191^1 237

tion between treatments, however, is not much higher than the varia-
tion in values between plots.

If quantity to a certain extent makes up for quality, the crop
index (product of yield figure and corresponding value of grade
index) should give a conception of the return values of various
treatments.

The following resume, based on average crop indexes and giving
a value of 100 to the control, presents an evaluation of the return
from the use of the various sources of phosphorus. They may be
referred to as relative crop values.

No phosphorus

100.

Steamed bone

101.6

Precipitated bone

105.2

Triple superphosphate

108.6

Calcium metaphosphate

117.6

Potassium metaphosphate

98.0 Av.

of two good plots

Potassium metaphosphate

74.5 Av.

of two inferior plots

Potassium metaphosphate

85.9 Av.

of all four plots

Potassium calcium metaphosphate

85.0 Av.

of two plots

For comparison, a two-year average of corresponding values is
given below (with the exception of potassium calcium metaphosphate,
for which data of only one year values are available).

No phosphorus 100

Potassium metaphosphate 100 (at best)

Steamed bone 101.9

Triple superphosphate 104.6

Precipitated bone 106.6

Calcium metaphosphate 113.6

These two-year averages agree closely with results of the present
year, with the exception that the positions of precipitated bone and
superphosphate are reversed. If it be recalled that the triple super-
phosphate had a tendency to produce an undesirable reddish cast of
the cured leaf, this per se reduces the possible value of the material
in cigar leaf production, in particular as regards wrapper tobacco.

Therefore, the rank of the phosphorus sources tested, consider-
ing their relative quality, would be as follows:

1. Calcium metaphosphate

2. Precipitated bone

3. Steamed bone

. 4. Potassium metaphosphate

5. Potassium calcium metaphosphate

6. Triple superphosphate

Chemical Analyses

Samples of tobacco grown with the various phosphorus carriers
were collected from the replicates to make up one composite sample
of long seconds and one of long darks per treatment. They were
dried, ground to a fine powder and then analyzed with respect to

-■••>>

Connecticut Experiment Station

Bulletin 457

content of phosphorus, potassium, calcium and magnesium. The re-
sults on phosphorus are shown in Table 7.

It is seen, that the phosphoric acid content varies little, about
half of one percent. Tobacco fertilized with precipitated bone and
calcium metaphosphate contained the least phosphorus, particularly
in the '"seconds." In considering crop removal of phosphorus, how-
ever, we find in the following summary a rather uniform utilization
of the phosphorus available in the soil.

Table 7. Phosphorus Content of Cured Tobacco. Air Dry Basis.
Crop of 1941.

Source of phosphorus

Grade

Plot no.

Percent

Av.

None

LS
LD

Pll

0.45

0.55

0.50

Precipitated bone

LS
LD

P12

0.41
0.53

0.47

Triple superphosphate

P13

0.46
0.57

0.52

Steamed bone

LS
LD

P14

0.43
0.55

0.49

Calcium metaphosphate

LS
LD

PIS

0.38
0.52

0.45

Potassium metaphosphate

LS
LD

P16

0.49
0.53

0.51

Potassium calcium metaphos-
phate

LS
LD

P17

0.50
0.52

0.51

Average removal of phosphoric acid (P*Os) by yield of leaves
from various phosphorus treatments.1

Check

Precipitated bone
Triple superphosphate
Steamed bone
Calcium metaphosphate
Potassium metaphosphate
Potassium calcium metaphosphate

11.76 pounds per acre

11.55 pounds per acre
13.09 pounds per acre
11.49 pounds per acre
11.33 pounds per acre

10.56 pounds per acre
9.7() pounds per acre

The check, precipitated bone, steamed bone and calcium meta-
phosphate come readirj within the range of average phosphorus re-
moval (11.56 pounds per acre), while triple superphosphate removed
more, and the two potash phosphates removed less, than the average.

From this it is suggested that triple superphosphate alone fenders
more available phosphoric arid than any of the materials tested.

A detailed report on the analytical results on potassium, calcium

ami magnesium is not given here since no significant differences due
to treatments were apparent. The average potash (K»0) content

'Stalks remove about as much P.O. as the It
bi iboul twlci iii. amounts given.

IV.'.-., Ill'll

total crop removal \\ « uld

Tobacco Substation Report for 1941 239

was 4.09 ± 0.206 percent, calcium (CaO) 5.75 ± 0.1 percent and
magnesia (MgO) 1.70 ± 0.066 percent. Analytical results give little
or no explanation, in particular to the behavior of calcium meta-
phosphate which ranked the highest in the present investigation. It
is possible that this material has a favorable influence on rendering
other nutrients more available, and this influence may be extended
to reactions in the plant tissues.

THE EFFECT OF SOURCE ON MAGNESIUM ABSORPTION

BY TOBACCO

T. R. SWANBACK-

The role of magnesia and its place in cigar leaf production are
rather well established through extensive work at this Station. (See
Bulls. 350 and 386). The tobacco grower in the Connecticut Valley
who avails himself of the soil testing service keeps informed on the
status of magnesia content in his land. Although many of the mate-
rials used in tobacco fertilizers contain more or less magnesia, it is
often necessary to include a special carrier. Under conditions where
it has been advisable to use lime containing magnesia, the question
has often been asked whether magnesian limestone (dolomite) or
hydrated magnesian lime is more effective in producing the desired
results in the same season that materials are applied.

In an attempt to find an answer to this question a field was
selected which was low in fertility (soil reaction pH 4.8) and which
had not grown tobacco for at least 15 years. The field was divided
into four one-twentieth acre plots, one of which did not receive any
liming material.

The remaining three plots were treated as follows :

Pounds per acre of
Material CaO MgO

1. Hydrated magnesian lime 800 300 200

2. Magnesian limestone 1000 300 200
o jLandplaster x 1000 300 10}.

(plus Emjeo (Anhydr. MgSO*) 190J

The entire field was fertilized uniformly with an 8-4-8 mixture
at the rate of 2,500 pounds per acre. Tobacco was planted crosswise
to the lime applications.

Vigorous growth was observed on the three treated plots, while
the size of plants on the check plot was noticeably smaller.

While the main purpose of growing the crops was to determine
the content of magnesium and possibly calcium in the cured leaves
from the various applications, it may be of interest to learn about the

1 Land plaster and magnesium sulfate were included as a treatment for comparing
a neutral supply of CaO and MgO versus the lime materials which offset a part of the
soil acidity.

240

Connecticut Experiment Station

Bulletin 4-.~-7

effect on yield and grading. On the sorting table all the tobacco
from this field was considered to be of very good quality, with satis-
factory texture and color, except for the plot receiving landplaster
(calcium sulfate) and magnesium sulfate. Here, the fillers (leaves
closest to the ground) were of a blackish color (known to the trade
as "black tobacco'') and, in general, the tobacco from this treatment
was inferior in quality to the control and the two lime treatments.
In this connection, it should be pointed out that landplaster is not
recommended for application to tobacco land that is too acid. As
has been pointed out earlier, (Bui. 350:477 and Bui. 444:260), land-
piaster may be emploj^ed only on tobacco soils having a satisfactory
reaction (pH).

Table 8 lists yield and grading data. In line with field observa-
tions, it is found that the control plot produced the lowest yield,
while hydrated lime and landplaster produced almost identical yields,
about 300 pounds per acre more than the control, and magnesian
limestone produced about 480 pounds more than the control.

The grading, as indicated by the grade indexes, again shows
that the landplaster treatment falls below the rest in quality.

Table 8. Yield and Grading Records of Magnesian Lime Test. Crop of 1941.

Yield

Treatment

per
acre

1978

Percentage of grades

Index

Grade

Crop

Control

.440

870.3

Hydrated Mg

lime

2295

.478

1097.0

Landplaster +

Emjeo

2280

36 f

.394

898.3

Mg limestone

2460

34 | 1

.471

1158.7

In considering the crop index (which is the product of the yield
figure and corresponding value of the grade index) it is still more
evident that the two magnesian lime materials gave a far better re-
turn than the control and landplaster treatment.

From computed relative crop values (crop index of control ==
100), the following resume is obtained:

Control

Landplaster -+- Emjeo

Hydrated magnesian lime

M.-uMicsian limestone

100
103.2
111.5
133.1

Once during the growing season (mid-July) and later, after the
<t<i|> bad been removed (October) samples of soil were collected
from the Eour plots. Reaction and content <>!' replaceable calcium
and magnesiam (Morgan method) were determined on these samples.

The results are round in Table !». With the exception of mag-
nesiarj Limestone, do appreciable change in reaction was r fleeted

Tobacco Substation Report for 1941

241

through, the use of various liming materials. Replaceable calcium
increased during the season, apparently through nitrification or other
biological processes in the soil.

If it be assumed that 50 pounds of magnesium per acre was the
original content of the soil and that a small amount was incidentally
supplied in the fertilizer, all the magnesium supplied as magnesium
sulfate (Emjeo) and magnesium limestone was found to be replace-
able, while hydrated lime was not so effective in this respect.

Table 9.

Soil Reaction and Content of Replaceable Calcium and Magnesium
in Soil of Lime Experiment Plots.

Calcium

Magnesium

Treatment

July

Oct.

July

Oct.

July

Oct.

Control

Landplaster-f- Emjeo
Hydrated lime
Magnesian limestone

4.90
4.84
5.04
5.10

5.10
5.10
5.10

5.50

400
750
750
800

800
1000
1000

900

50
250
100
250

25
100

50
250

Leaf Content of Magnesium and Calcium

Representative samples of lights (L) mediums (M) long seconds
(LS) and long darks (LD) from the four treatments were ground
up finely and analyzed1 for calcium and magnesium. The results
are given in Table 10. In examining the data it is seen that, on the
average, slightly more magnesium was deposited in the leaves when
hydrated lime was the source than when the limestone was used.

It is of interest to note that calcium in hydrated lime was less
readily taken up by tobacco than that from limestone. This, how-
ever, does not necessarily mean that the calcium in limestone is more
readily available, but that the magnesia in this material may not
have been so readily available as that in the hydrated lime. The
reciprocal or antagonistic actions of the three main bases, cal-
cium, potassium and magnesium — ■ — function to establish an acid-
basic balance within the plant. That is, any one of the three bases
makes up for the insufficiency of one or both of the others (See Bui.
444:256).

Emjeo (magnesium sulfate) and landplaster in the present com-
parison were responsible for the highest leaf contents of both mag-
nesium and calcium. This is in line with an earlier report (Bui.
386:584) that Emjeo furnishes more readily available magnesia
than does magnesian lime. Calcium in landplaster (calcium sulfate),
because of its chemical composition, as would be expected furnished
more readily available calcium than either of the lime materials.

The results of this investigation suggest that either one of the
two materials, magnesian limestone and hydrated lime, may be used

1 By the Chemistry Department of the New Haven Station.

242

Connecticut Experiment Station

Bulletin 457

as a source of magnesia with about equal advantage, although the
limestone might be safer to use in fertilizer mixtures of any com-
bination.

It ma}^ be concluded that, while there may be a choice between
the two lime materials when relatively small quantities of lime are
required, if larger amounts must be applied (1,500 pounds up to one
ton or more), calcic limes should be used in order to prevent a sur-
plus content of magnesia in the leaf. The magnesia requirement in
the latter case is most readily filled in the fertilizer by inclusion of
some magnesian lime or Emjeo.

Table 10. Context of Magnesium Oxide and Calcium Oxide in Tobacco From
Air Dry Basis. Lime Plots. Crop of 1941.

Liming materials

Grade

CaO

Av.

MgO

Av.

4.96

1.02

4.16

.84

Check

4.15

4.24

.76

.85

3.68

.77

5.11

1.94

Kydrated magnesian lime

4.78

1.59

4.48

4.63

1.56

1.60

4.13

1.29

6.00

1.97

5.18

1.80

Landplaster — Emjeo

4.77

5.21

1.58

1.75

4.88

1.64

5.60

1.74

5.06

1.40

Magnesian limestone

4.96

5.07

1.22

1.37

4.66

1.12

RESIDUAL EFFECT ON STABLE MANURE

In the Tobacco Substation Report for 1940 (Bui. 444:246) the
results of the firsi year of an experiment to measure the residual or
after-effect of a preceding ten years of heavy manure application
wen- described. During the first year, although the usual applica-
tion of commercial fertilizer was used on all the Held, those plots

which had manure during the previous years gave an increase of 25

percent ill yield and .">•''. percent in grading over the other parts of
the field. I'll i> experiment is to he continued through a series of years
in order to determine how long these effects will last.

The same four manure plots and corresponding controls were
measured in L941, as in L940. During the summer the differences

between the manure plots and the other parts of the held were not
SO marked as in L940 hut tin- leaves were a little darker green and
the growth a little more luxuriant. When the cured tobacco was on

the sorting bench, no very consistent differences lie) ween them were
observed with resped to color, texture, vein-- and other quality char-

Tobacco Substation Report for 194-1

243

acteristics. The yields and grading of the plots are shown in Table
11. These data do not show any improvement in grading, but there
was an increase of 136 pounds to the- acre (T percent) in yield. This
is a smaller increase than was shown the first year but still shows
that there was a distinct residual effect two years after any manure
was applied.

Table 11. Yield and Grading Records of Residual Manure Plots and Controls.
Crop of 194.1.

Yield, lbs.

Plot no

per acre

Percentage of grades

Grade

index

treatment

Plot

Av.

Plot

Av.

Manure

1913

.386

two years

2100

.462

2194

2086

.381

.410

M4
Mchl

2138

.409

No previous

1819

.384

manure

Mch2

1931

.443

Mch3

2063

1950

.382

.409

Mch4

1988

3 J

.425

FURTHER EXPERIMENTS ON STARTER SOLUTIONS

From previous trials with starter solutions it was learned that
by necessity they should be rather weak (Bui. 444:260-264). Eec-
ognizing this fact, in repeating the tests in 1941 the solutions used
in the setter barrel were of a weak concentration.

The following solutions and concentrations were employed :

I. Nitrogen as nitrate of soda, 3 pounds per setter barrel (50

gallons of water)
II. Nitrogen and potash; 3 pounds nitrate of soda and 1 pound
of sulfate of potash per setter barrel.

III. Nitrogen, phosphoric acid and potash, according to following
formula :

50 pounds superphosphate (16 percent P205)

32.5 pounds nitrate of soda

13.5 pounds sulfate of potash

4.0 pounds Emjeo (magnesium sulfate)

100.0

Three and a half pounds of this mixture were used for 50 gallons of
water, furnishing plant food at a ratio of 5-10-7.

On a field of rather low fertility, that had been previously ferti-
lized at the rate of 2,500 pounds of 8-4-8 per acre, rows of tobacco
were planted, using plain water for check rows and, for alternating
rows, the various solutions. Thus, there was one check row, fol-
lowed by a row of solution I, a row of solution II and a row of
solution III. This procedure was repeated so that triplicate test
rows were obtained for check and treatments. The field was planted
on June 4 and harvested on August 21. Yield and grading; records

244

Connecticut Experiment Station

Bullet hi 457

are given in Table 12. From the data presented it is seen that
starter solutions were decidedly beneficial. The results expressed in
terms of relative crop values are :

Check = 100
I. Nitrogen = 128.5
II. Nitrogen and Potash = 128.0
III. Nitrogen, phosphoric acid and potash = 127.1

Table 12. Yield and Grading Records of Starter Solution Tests. Crop of 1941.

Yield, lbs.

Percentag

3 of grades

Grade index

Treatment

Plot no.

Plot ] Av.

B
20

Plot

Av.

1790

.213

Gieck

1759

1832

.316

.300

1947

.372

I A

1862

.383

I B

2063

2016

.448

.405

I C

2123

1
10

8
10

.385
.348

II A

1792

"32

N & K

II B

1892

1918

.344

.367

II r

2070

.408

III A

1805

.326

N, P & K

III B

1816

1883

.393

.371

III c

2029

.395

The results indicate that using relatively weak starter solutions
is beneficial, although it is strongly suggested that nitrate of soda
alone will benefit both growth and quality more effectively than mix-
tures of several plant foods. In using nitrate of soda in the setter
barrel it is suggested that a stock solution be made up, such as 50
pounds to 50 gallons of water, of which not more than 3 gallons
should be used for a setter barrel.

USE OF CARBON BLACK TO ACTIVATE GROWTH EARLY
IN THE SEASON

It is commonly known that black surfaces absorb heat rays more
efficiently than surfaces of other colors, with a minimum of absorp-
tion when the surface is non-colored or white.

Similarly, a dark colored soil absorbs more heat than a Light
colored -..il. If. therefore, a light colored soil could be darkened

by some artificial means, it should absorb more of the sun's heat.

This would probably benefit plants set out. early in the season when
cold night- would he ;i setback to growth. A black material placed
around plants would cause the soil to ahsorh and retain more heal

(depending on moisture) and build up a reserve for the night.

In order to determine what effect, if any. a blackened area around

tobacco plant- might have on growth and quality, a preliminary trial

was made in I he spring of l'.M 1.

Tobacco Substation Report for 194-1 245

A quite uniform field was selected (field IV) and fertilized with
a balanced mixture (2,500 pounds of 8-4-8 per acre). Seven rows of
tobacco (150 feet long) were used for the experiment. To four
of these carbon (Solium1) was distributed in bands 4 inches wide on
either side of the row. Alternate rows were left untreated as controls.

The carbon black was applied at the rate of 850 pounds per acre,
although it is claimed that a 200-pound rate would be sufficient for
other crops. The band on the surface of the soil was undisturbed for
about ten days (carbon black applied on June 2 and cultivated the
first time on June 12) . In the early stages of growth it was observed
that at least three of the four treated rows produced somewhat larger
plants than the controls. It was thought that the material might have
induced more favorable conditions for nitrification. Hence, concen-
tration of soil nitrates was determined at three different times during
the arrowing season. The results are listed below :

Seasonal

Treatment

Pounds per acre of Nitrate Nitrogen
June 10 June 17 July 8

average

53.6 95.8 51.0

Carbon black

56.4 157.6 85.6

100

This material (Solium), claimed not to contain nitrogen as an
impurity, apparently greatly accelerated the processes of nitrification
— about 50 percent for the trial period.

The tobacco was harvested on August 18 and, after proper cur-
ing, it was sorted in the Station warehouse. As judged on the sort-
ing bench, tobacco from the control rows was considered to be of very
good quality, with occasionally a few starved (yellowish) leaves.
The quality of tobacco from the carbon black treated rows was con-
sidered only fair. It was somewhat coarse, (as contrasted to the de-
sirable smooth, silky texture) and a considerable number of starved
leaves was found. The grading and yield data are found below.

Yield Percentage of grades Index-

Treatment per acre L M LS SS LD DS F B grade crop

Control 2172 9 4 31 2 37 1 10 6 .435 944.8

Carbon black.. 2311 7 6 28 1 37 1 13 7 .398 919.8

It is shown that the carbon black treatment produced a some-
what higher yield than the control, although the increase is not big
enough to cover the additional expense for material and labor. How-
ever, if the grading had been proportionally improved, that per se
might have warranted its use. The grade index for the control was
almost 10 percent higher than that of the carbon black. This gives
the crop index (product of grade index and yield figure) for the
control a value of about 945 as contrasted to that of the treatment,
920. These values, on a relative basis with 100 for the control, allow
only 97.4 for the carbon black application.

1 "Solium" is a commercial grade of carbon black furnished by Binney & Smith
Company of New York.

246 Connecticut Experiment Station Bulletin 4r>7

The result of one season's trial suggests no real advantage in
employing a material, such as carbon black (Solium), for tobacco.
No doubt, however, the material may be used to facilitate biological
activities on soils where there is need for such a speeding up and for
crops other than tobacco. With respect to tobacco in general and
cigar leaf tobacco in particular, quality is often more important than
yield.

It is possible that, in the present test, most extensive production
of nitrates occurred at a time when the plants were still too young
to fully utilize the plant food. This is indicated by the exceptionally
high level of nitrates on June 17 (157.6 pounds per acre) ; and, by
the fact that the percentage of "darks" (LD and DS) was no higher
for the carbon black tobacco than it was for the control, thus in-
dicating that there was no oversupply of nitrogen when the crop
was maturing. (A high percentage of "darks"' is usually considered
an indication of an oversupply of nitrogen in the soil.) It is also
possible that a portion of the extra-early production of nitrates under
the carbon black treatment majr have been leached below the root
zone by June rains.

FURTHER INFORMATION ON IRRIGATION OF TOBACCO

In previous reports1 it has been shown that irrigation of tobacco
during dry periods can be quite effective and profitable if measures
are taken to prevent depletion of nitrate in the soil during the process.
Further data along the same line were obtained by an experiment in
1941, although the season as a whole was not a good one for irrigation
because the rainfall was sufficient and well distributed except for one
period in mid-July.

On July 23 the tobacco on one coarse sandy field was wilting
badly and was therefore used for this test. One-third of the Held was
irrigated by running water down between the rows (method described
in Bul. 391). Another third was not irrigated at all. The last
third was irrigated as mentioned but, in addition, nitrate of soda at
the pate of L50 pounds to the acre was sprinkled into and dissolved
in I he water before it sank into the soil. The purpose of this was
to replace any nitrate that would be leached away. The rate of
water application was equivalent to about one and one-half inches of
rainfall. It was planned to repent this a week later hut timely rains
made irrigal ion unnecessary.

When i he cured crop was sorted, a high percentage of starved
yellow leaves from the plots irrigated without nitrate indicated that
the fertilizer had been leached away. Such starvation was not ob-
served on the irrigation plots to which nitrate of soda had been

added. The yield and sorting records are shown in Table IS.

'Conn, si.. Bul, 801, p, 61 and Bul, n. p, 2G4.

Tobacco Substation Report for 191^1

247

The data show that, on a sandy soil, irrigation alone may be
more harmful than beneficial. It resulted in a reduction of 26 per-
cent in the value of the crop (crop index). But when nitrate of soda
was added to the water there was an increase of 15 percent in the
value of the crop. Both yield and grade index were materially in-
creased. These differences are larger than we have had in tests of
previous years but are all in the same direction. It is not likely that
such large differences would be found if the soil was heavier and
less prone to leaching. However, it is the lighter soils which the
grower usually irrigates, because they are the ones that first suffer
from drought.

Table 13. Yield and Grading Records of Irrigation Plots. Crop of 1941.

Treatment 1

Yield,
pounds
per acre

Percentage

of grades

Grade
index

Crop

index

Not irrigated

1556

.362

563.27

Irrigated alone

1526

—

.273

416.60

Irrigated with
addition of
nitrate of soda

1649

.393

648.06

1 Relative values based on crop index.
Not irrigated 115

Irrigated alone 74

Irrigated nitrate 100

The results of all experiments to date warn against the danger
of this type of irrigation on 'leachy" soils unless the nitrate content
of the soil is kept up.

LUMARITH AS A SUBSTITUTE FOR GLASS IN SEED BED SASH

In our report for last year (Bui. 444, p. 269) the advantages of
lumarith (a light, transparent, plastic, cellulose acetate) were de-
scribed. The results of the first year's test were favorable and war-
ranted a continuation of the trial. Sections of the seed bed were
therefore covered in 1941 with the same lumarith sash that we had
used in 1940. The sash had been kept over winter in a curing shed.
By spring the plastic had become very brittle. Unless the sash was
handled very carefully, the lumarith tended to split and break loose
from the wooden frames. Before the seed bed season was over, most
of the material had become unserviceable and had to be replaced
with glass sash. Unless this fault can be overcome, lumarith can
hardly be recommended because it is obviously impracticable to
re-cover the frames each year.

There were no observable differences in growth of the plants in
the seed beds covered by lumarith. They did not grow any faster
than those under glass, nor was there any other difference in vigor,
color of leaves, etc.

248

Connecticut Experiment Station

Bulletin 457

It has been claimed by some experimenters that lumarith might
have some effects that would be expressed in improved vigor in the
field after transplanting. In order to test this, six rows of plants
from the lumarith section of the bed were set in a field, each row
alternating- with a row of plants of the same age from the glass-
covered parts of the bed. As far as could be observed there were no
differences in growth betweeen the alternate rows in the field during
the summer. Each was harvested, cured and sorted separately. The
3Tield and sorting results are shown in Table 14.

Table 14. Yield and Grading Records of Tobacco From Lumarith and Glass
Covered Beds. Crop of 1941.

Sash covering

Yield,
pounds
per A.

Percentage of grades

Grade
index

Crop

M 1 LS

39
39

index

Lumarith
Glass

1853
1913

2 40
1 1 35

2
2

2
9

.421
.398

780.09
761.37

The yield was higher in the rows from the glass-covered beds
but the grading a little better on the lumarith. The differences are
probably too small to be significant or to indicate that any improve-
ment in yield or quality was produced in the crop by growing the
plants under lumarith.

TOBACCO DISEASES IN 1941

P. J. AXDERSON

Diseases of tobacco caused very little damage during 1941.
Downy mildew was prevalent for a short time in the seed beds but
caused Little trouble later and was almost absent from the fields.
Not a single case was seen or reported of wildfire, blackfire, frenching,
leaf blotch, sore shin or wet stalk rot. Of quite minor importance
were dam ping-off, bed rot, black and brown root rot, hollow stalk and
(lie various forms of pole rot.

Some Experiments on Control of Downy Mildew

The most common method of applying PDB is (<> place the crys-
tals in shallow wire baskets, about 2 inches wide and L0 inches long.

These arc supported by nails driven into the side boards of the \>v>.\s.

Although the early experiments showed that, under favorable temper-
ature conditions, one basket to each two sashes is sufficient when one
ounce of crystal- to each four square yards of bed is used, many of
the growers arc using one basket to each sash, "staggering" them on
alternate side- of the hcd. The degree of control obtained has varied
greatly from farm to farm depending ,,|, (a) tightness of beds, (l>)
intervals between application, (c) time of starling treatments, (d)

lengl h of t real tnenl . dr.

Tobacco Substation Report for 194-1 249

On the whole, however, it must be admitted that control of
mildew by PDB, according to the method of application we have
used, has not been entirely satisfactory, especially when the nights
are cold. It is possible that a more thorough distribution of the
gases in the bed might give better control.

In some tobacco sections of the country where cloth covers are
used over tobacco beds, the crystals are distributed over the entire
surface of a thin cloth which, in turn, is covered with a heavier cloth.
This method gives a wider distribution of the crystals and, possibly,
a more nearly equal gas concentration in the air than can be obtained
by the basket method. This is reported to give satisfactory control.
Since this method would not be very practical under our glass sash,
a modification of the same principle was tried in our beds at the
Experiment Station in comparison with the wire basket method.

Light frames 3x5% feet in size were covered with a thin cheese
cloth. These frames were then supported under the glass above the
plants by spike nails driven into the sides of the bed. The frames
were spaced one to each 6 feet of bed. One ounce of PDB crystals
was distributed evenly over each cloth frame every second night.
In another section of the bed a similar amount was used in baskets,
one to each sash, but staggered. A third section of bed was left
untreated as check. Treatments were applied on May 14, 17, 19, 21,
23, 26, 28, 30 and on June 1, 3, 6, 9 and 11. The bed was inoculated
thoroughly on May 15 and on June 2 by sprinkling all the bed
with a suspension of spores in water.

On May 24 mildew began to appear on the check bed and con-
tinued to spread until there was 100 percent infection. On June 1
there was a little infection on the basket section. None appeared
on the cloth section.

The cloth method thus gave better results than the basket method
in this test, indicating that more thorough distribution of crystals
may improve the degree of control.

Removal of PDB Crystals. The usual practice is to remove
the PDB from the beds about 8 A. M. daily. If the crystals are
kept in the beds until it becomes too warm there is danger of plant
injury from too great a concentration of the gas. This is indicated
when the plants begin to fade to a yellowish cast. But, on cloudy
days it does no harm to keep the crystals in the bed all day.

One progressive grower suggested that we should gauge the time
of removal by the thermometer rather than the clock. To test his
conviction he kept thermometers in the beds and removed the baskets
only when the temperature came up to 80° F. He did not have
mildew in any of his beds during the setting period although he had
mildew there regularly for several preceding years, and there was

250 Connecticut E&peri/ment station Bulletin 457

mildew in the beds of his neighbors. Unfortunately, he did not
leave any untreated beds for a control this year.

Another grower found it too laborious to remove the baskets of
crystals each morning and. therefore, he left them in permanently
I nit was careful to raise the sash and ventilate the bed during the
day. He escaped mildew. The method is rather wasteful of mate-
rial but. saves labor.

Liquid Sprays. Although a considerable list of liquid sprays
have been tried here for control of mildew, none of them has given
satisfactory control. Most of them have caused leaf burning, or
other types of injury, or have failed to control mildew. Neverthe-
less, new ones have been tried each year. One which we tried this
year was the most satisfactory of any of the sprays we have yet
found. This is a copper soap spray called "Flordo" which has been
used with good results in Florida.1 In our tests this was prepared

as follows : 1 pound of copper sulfate was dissolved in 15 gallons
of water, and 4 pounds of soap (soap flakes) in 15 gallons of water.
These two solutions were then stirred together. A small amount of
curd that was formed was removed by straining through cheese cloth.

This was sprayed on the growing plants twice a week for four
weeks. These plants and the unsprayed controls were inoculated
twice with spores of mildew. The unsprayed checks finally became
100 percent infected. Although the section sprayed with Flordo did
not remain entirely free from disease, infection was light and did
not cause serious damage. Some of the leaves were burned by the
spray but not severely. Results indicate that this material should be
subjected to further trial. A good spray might appeal to some of the
growers more than the fumigation method now in general use.

Exit Wildfire

This is the fir>t season in •_'<> years that the writer has failed to
see or hear report of a single case of wildfire in the Connecticut Val-
ley. After its spectacular outbreak and destructive spread in the
early Twenties, wildfire began to be less prevalent each year. This

gradual tapering off process continued until during the late Thirties
it was unusual to find more than a dozes cases any year, hut each
year there were always a few. Now it seems to have dropped out

completely. Such behavior ^n- any plant disease is quite unusual
iii the annals of plan! pathology.

DELAYED FROST INJURY TO TRANSPLANTS IN JUNE

During the first two weeks of June light frosts were reported
from scattered localities after tin' plants were started in (lie fields.
I'ro-t u;iv in,, -i genera] on June L2, bu1 there were also reports of

.... w. n. Flordo Spray. Fla. Ker, Bxp, Sta, Press Bulletins B04 (1987)
and 647 I L940).

Tobacco Substation Report for 19^1

251

quite localized frosts on other nights. The chill was not severe
enough to cause the leaves to turn black and die. In fact, no one
reported injury at that time. But within the next two weeks grow-
ers began to bring in plants with peculiar markings which they were
unable to diagnose. Having forgotten about the earlier frosts, they
feared that another new disease had appeared here.

The most characteristic symptom of frost injury is the presence
of broad white chlorotic bands, equally distributed on each side of
the midrib and usually confined to the basal part of the leaf (See
Figure 2.) The tips and upper parts of the leaves are commonly
green and normal. The outer margin of the basal part may also be
green, but frequently the chlorotic bands involve all the web of the
basal part. The whitened, affected base fails to expand as the leaf

Figure 2. Delayed frost injury showing at
center of young tobacco transplant.

grows and, therefore, appears narrow and pinched, making a sort of a
handle to a spoon-shaped leaf. The margin of the injured part is
usually wavey and the leaf variously distorted. The older, bottom
leaves may be quite normal. Only the leaves that were quite young

252 Connecticut Experiment Station -Bulletin 457

and tender at the date of the frost are involved. The affected area of
the leaf may be solid white or may be variously speckled and peppered
with green.

In general the injury was found to be confined to limited parts
of the field. All three types of tobacco were affected. Observations
later in the year showed that all leaves above the chlorotic lower
ones developed normally, and the plant as a whole was not seriously
injured.

A similar condition occurred here in 1926 following a heavy frost
on June 16 (See Tobacco Sta. Bui. 8:55 for description and illus-
tration).

Tobacco Substation Report for 1941 253

MOSAIC OR CALICO DISEASE OF TOBACCO

The season of 1941 was marked by unusual freedom from damag-
ing diseases of the tobacco crop. But, contrary to this general state-
ment, mosaic (known also among growers as calico, mongrel, brindle,
gray top and rust) was more abundant than we have known it to be
for many years. Its sudden prevalence aroused renewed interest
among growers, and the Substation received numerous inquiries about
its cause, spread and prevention. In view of this interest and the
fact that we have been experimenting for several years on a method
of control, about which information has not been previously pub-
lished, this seems an opportune time to present an up-to-date picture
of our present knowledge of tobacco mosaic.

It has been 12' years since we published a comprehensive article
on mosaic (Tobacco Sta. Bui. 10, p. 75). In the interim the problems
of mosaic diseases of plants have been extensively investigated by
scientists. Their findings have greatly advanced our understanding
and changed our conceptions of the causes of these diseases. Numer-
ous articles by plant pathologists, physiologists and chemists have
been published in journals and bulletins, but they are not available
to many of our readers or are too technical for the practical tobacco
man. The purpose of this article is to present in non-technical lan-
guage the latest pertinent facts about mosaic.

Symptoms. Every experienced tobacco grower recognizes an
ordinary calico plant in his field. The mottled appearance of the
leaves, with splotched areas of greenish yellow between other areas
of normal green, is familiar to all (Figure 3, top). Symptoms show
all graduations of intensity. Sometimes the differences in shade of
color are barely noticeable; at the other extreme, the light chlorotic
areas of the leaf may be bright yellow to almost white and therefore
stand out very sharply in contrast. Also, the pattern or mosaic,
formed by the irregular alternating chlorotic and normal parts, is so
extremely varied as to defy description. In some types, however,
the darker areas have a tendency to follow the veins (Figure 3, bot-
tom).

Attempts have been made to distinguish and name several types
of mosaic according to differences in leaf symptoms, such as pattern
or color of the chlorotic areas. There are, however, so many inter-
graduations between field types that, except for the mosaic specialist,
such a classification adds nothing to clarity of understanding. In
severe cases young leaves may become distorted or "puffed" and are
inclined to be abnormally narrow. Plants affected early become
dwarfed, do not make a normal growth and are practically worthless
when mature. Late infestations with only a few of the top leaves
showing the symptoms, frequently not severe, are commonly known
as "gray top" by growers.

254

Connecticut Experiment Station

Bulletin 4.'i 7

Figure .^. Tobacco leaves showing patterns of mosaic: Top,
mo i common pattern of mottling; center, red rust, a symptom oi ca
marked l>3 irregular, dead, brown patches; bottom, the pattern in wl
the dai 1. ai ea follow the veins.

Tobacco Substation Report for 194-1 255

But there are other symptoms which growers do not always real-
ize are manifestations of the same disease. This is particularly true
of the necrotic or dead spots of various shapes and colors that develop
in the leaf tissue. These are of two general types and have been
called white rust and red rust. The white rust, also called fleck, is
marked by numerous small white spots peppered over the leaf. In
the red rust type the spots are larger, more irregular and of a reddish
brown color (Figure 3, center). This may be so severe as to cause
death of the whole leaf. The reel rust type, if more diffused, is some-
times called mosaic burn and appears often on the upper leaves of the
plant. Burning of the top leaves usually results from the spread of
mosaic while topping. Since such leaves often show no mosaic mot-
tling, the grower is not aware of the connection.

Extent of Damage. Although mosaic recurs here every year,
it is rarely a disease of major importance. In this section as a whole
only a fraction of one percent of all the plants set contract the
disease at a sufficiently early stage to suffer serious deterioration in
quality or yield. An occasional field is found where the loss is
heavy, and it is the occurrence of such cases that gives importance
to the disease and the need of control measures.

The extent of damage to a plant depends largely on the stage of
the plant's development at the time it becomes infected with the dis-
ease. A plant infected in the seed bed probably never attains sufficient-
ly normal growth for its leaves to be suitable for cigar wrappers or
binders. They might possibly serve as cheap scrap chewing tobacco.
On the other hand, if infection occurs at the time of topping, the
damage may be practically negligible, though, even at this late stage,
considerable "burn" of the top leaves may result.

There are three sources of loss. (A) Dwarfing of the plants
reduces yield. (B) The dead spots (white and red rust) reduce
the value of the leaves somewhat in proportion to prominence of the
spots. (C) A mottled leaf, when cured, has uneven colors, dead
finish and is not elastic.

In a three-year experiment in Maryland, McMurtrey1 found that
early infestations caused a loss of 55 percent of the gross value of
the crop. In another three-year test in Kentucky, Johnson and Val-
leau1' found that early infection reduced the yield 31 percent and the
total value 40 percent. Even when infection occurred at topping time,
the quality of the tobacco was reduced 25 percent. The losses in
both of these tests are calculated on the basis of 100 percent infec-
tion — a condition that rarely occurs naturally — but they serve to

1 McMurtrey, J. E. Effect of mosaic disease on yield and quality of tobacco.
Jour. Agr. Res. 38:257-267.

2 Johnson, E. M. and W. D. Valleau. Effect of tobacco mosaic on yield and quality
of dark fire cured tobacco. Ky. Agr. Exp. Sta. Bui. 415. 1941.

256 Connecticut Experiment Station Bulletin -±57

show that an}' degree of infection is damaging both to yield and
quality.

The Causal Agent. Ever since tobacco mosaic was described
GO years ago, a considerable variety of theories on its cause have been
advanced and supporting evidence published to back each theory.
Only in the last few years has the true cause been demonstrated and
all the other alleged causes relegated to interesting past history.
Mosaic is now known to be caused by a virus, appearing in the plant
sap as minute rod-like particles of a protein nature which have the
remarkable characteristic of being able to multiply indefinitely in the
living cells of all parts of the tobacco plant.

According to recent investigations1 an increase in these parti-
cles is at the expense of chromoprotein, which is in the protoplasm of
all the cells of the plant. "Whether or not the virus is composed
of living organisms, it has definite parasitic properties. The cell
cannot synthesize the virus de novo; a small particle of it must be in-
troduced into a living cell in order to cause infection. Here it mul-
tiplies and spreads to other cells. When introduced into a tobacco
plant, the virus spreads rapidly to the roots and to the newly develop-
ing leaves, but extreme^ slowly to leaves already fully grown. The
symptoms described above will appear on the leaves that were
growing rapidly (rust) and on leaves which were very small (mot-
tled) when infection occurred. All new growth will likewise be
mottled. The particles of virus in the plant juice, which are desig-
nated as protein molecules by some investigators, are very minute, so
small that they wrill pass through the pores of very fine filters. It
would require about 125,000 of them placed end to end to span one
inch.

Spread and Overwintering. Mosaic is extremely infectious and
will spread from the most minute quantity of the virus transferred
to the cell of a growing plant. From this point it quickly spreads in
the sap to the roots and to the growing point of the plant. Once
a plant is infected, it never recovers, since it has no way of eliminat-
ing the virus. "When, in handling infected plants, the juice gets on
the hands of the workman, he need only touch or rub his fingers
over the leaf of a healthy plant to infect it. Any virus introduced
into seed beds would be, thoroughly disseminated by weeding or pull-
ing the plants for setting. "When there are a few infected plants
established in the field, the virus may be spread around on hands,
clothing, tools. i-\c. dnrin,<_r any cultural operations. Fortunately, it
is not spread by many of the common disseminating agents of fun-
gous diseases, such as wind and splashing rain. There is no conclu-
sive evidence that it is spread by insects.

Although the methods of dissemination in beds and field are well
known, the means by which mosaic first gets its start each spring are

i Woods Mark W. and II. >; DuBuy, Synthesit ol tobacco mosaic virus protein
in relation to leaf chromoprotein ai • n metabolism. iMiytui.nth. :«i ::«ts-:<:»o. mi.

Tobacco Substation Report for 194.1 257

not so obvious. Its method of overwintering, however, gives some
clue. In cured or dried leaves the virus will remain infective almost
indefinitely. Thus Johnson and Valleau1 found it is still active in
tobacco that had been kept in a case for 52 years. Its longevity
is probably the most important fact to be kept in mind in connection
with the prevention of mosaic: It will even survive in manufactured
tobacco, such as cigars, cigarettes and chewing tobapco, although in
smaller amounts than in the barn-cured tobacco.

Valleau has shown that in Kentucky the use of "natural" chew-
ing tobacco by workmen tending the beds is the common source of
initial bed infection. Badly infected beds have been observed in
Connecticut where growers have used tobacco refuse, raked from the
floor of curing sheds, as fertilizer. We visited a field in the summer
of 1941 where one part of the field had 75 percent mosaic plants, while
other parts of the field were relatively free of the disease. The in-
fection was traced to the fact that the owner had ground up tobacco
stalks from the previous year's crop and applied them as a fertilizer
to the area of lowest fertility at time of setting the plants. This
insured a thorough distribution of mosaic. In some sections of the
country perennial weeds belonging to the tobacco family are some-
times infected, and the virus is transferred to tobacco plants while
weeding. This does not appear to be a common source of infection
here, however.

A great deal of investigation has centered on the ability of the
virus to live in the soil over winter. It has been shown that in many
soils the virus survives the winter, but probably only a very low
percentage of infection may be traced to soil-borne virus from a
preceding mosaic crop. The virus may be in the still undecomposed
residues of the plants or may have been washed out into the soil it-
self. The percentage of virus that winters over in this way is ob-
viously quite small. Otherwise, it would not be profitable to grow
tobacco year after year in the same field. Every grower has seen
fields where infection was about 100 percent on the suckers that grew
up after a crop was harvested. Yet, a crop planted on that same
field the next year would as likely as not be free from mosaic. If all
the virus had remained active in the soil, there would be few healthy
plants in the new crop.

No doubt, the greater percentage of virus becomes inactivated in
the soil, especially in the upper layer which is stirred and well aerated
before setting. Virus, like other protein substances, is decomposed by
the action of soil organisms and thereafter cannot cause infection.
The residues of tobacco plants quickly decompose when incorporated
in the soil, especially if the soil is moist and well aerated. Investi-
gators have shown that the type of the soil may have an influence on
the ability of the virus to live over. This may explain the report

1 Johnson, E. M. and W. D. Valleau. Mosaic from tobacco one to fifty-two years
old. Ky. Agr. Exp. Sta. Bui. 361:264-271. 1935,

258 Connecticut Experiment Station Bulletin 457

by manv growers that certain spots in their fields are prone to show
mosaic more or less every year. The soil in these areas may he more
suitable for keeping the virus in an active condition.

Control. No spray or dust is effective in controlling mosaic.
Control measures must start with an understanding of the nature of
the disease and. particularly, its method of dissemination as described
above. Methods should aim, first, at preventing the introduction of
the disease into the bed or field in the spring and, secondly, at re-
moving infected plants which may spread it from plant to plant in
the field.

The following preventive measures have been found useful and
are offered as suggestions to growers whose crops are troubled with
mosaic.

1. Tobacco refuse from curing sheds, sorting rooms or other
sources should be kept entirely away from the seed beds. Sometimes
tools or bed sashes, which have been stored in sheds without being
carefully cleaned, may carry bits of diseased leaves to the beds.

2. If the stalks of a preceding crop are to be used on tobacco
land for fertilizer, they should be plowed under the surface as
thoroughly and early as possible to give them every opportunity to
decay. If stalks are from a mosaic crop, or if results from this prac-
tice in previous years have been bad, it is better to use them on land
intended for other crops.

3. Men who are weeding, pulling or setting, or handling the
crop in any way, should be discouraged from using tobacco. This
applies to the, use of the leaf in any form, but particularly in chewing
and pipe tobacco.

4. Plants should never be set from a bed known to contain
the disease. Mosaic plants are difficult to detect in the seed bed. If
only a few are found, it is quite certain that there are many other
diseased ones which have not been "'spotted." Rather than risk
spreading the disease to the field it is better to sacrifice the whole bed.

Second and third pullings from a bed are much more likely to have
mosaic than the first ones, because of spread while pulling.

■'. Jusl after the plants start in the field, "rogue" out any
diseased oik-. A.bou1 once a week, while the plants are small.1 a
workman should systematically inspect each row, pull up every

Calico plant ami put it in a basket. This should he done before cul-
tivating «u- performing other operations which might spread the
disease. The person who rogues should avoid touching any health]
plant, otherwise he may spread more disease than he removes. The

ba lo-l of diseased plants should he d ped far from any growing

U i -I.. hi I., large there Id too much danger of Bpread bj carrying them through
the.fleld.

Tobacco Substation Report for 1941 259

tobacco. The workman should thoroughly wash his hands before
hand lino; healthy plants again.

We regard this "rogueing" as a very essential measure of con-
trol. Both the Experiment Station farm and commercial growers
have used it with success for many years. If it is carefully done, no
other control measure should be necessary the remainder of the season.
Rogueing is practicable only where the percentage of infected plants
is small, but this is the condition in at least 95 percent of Connecticut
fields. Where the percentage is very high, it is better to plow under
the crop and replant from healthy beds.

6. If rogueing has not been successful, avoid spreading the virus
from diseased to healthy plants during field operations, even at the
time of topping and suckering. If there are several men working,
one of them may handle all the diseased plants ahead of the others
and not touch the healthy ones. This measure is of less importance
than the preceding since the direct damage at this stage is not great,
but it has some bearing on the practice mentioned in the next para-
graph.

7. Every precaution should be taken to keep the entire tobacco
farm free from mosaic. By carrying out sanitation practices the
grower reduces chances of infection from refuse, which holds no
danger if leaves and stalks are disease-free. Moreover, a soil which
does not harbor mosaic cannot spread infection. Some Connecticut
tobacco farms have had practically no mosaic for years because the
owners will not tolerate any sources of infection.

Mosaic Resistant Varieties. The perfect method of control-
ling any disease is to find or develop a strain or variety of the crop
which is naturally immune or so highly resistant to the disease that
need of further control measures is permanently eliminated. A resis-
tant strain of tobacco must also have satisfactory commercial quali-
fications. The incorporation of good characters in a resistant strain
may be the most difficult part of a breeding program.

Until 1933, it was currently believed that all varieties of tobacco
were equally susceptible to mosaic and therefore offered little chance
for the development of a resistant strain. Then Nolla and Roque1
found in Columbia, S. A., a variety of tobacco called Ambalema.
This is so highly resistant to mosaic that common symptoms are
absent, except for an occasional indistinct mottling of the lower
leaves. Although Ambalema does not have qualities comparable to
those of any types grown commercially in the United States, its factor
of resistance may be bred into our present varieties by hybridization
Several experiment stations and the United States Department of
Agriculture are endeavoring to get suitable commercial resistant
strains by using Ambalema as a parent. This hybridization pro-

1 Nolla, J. A. B. and Roque, Arturo. A variety of tobacco resistant to ordinary
tobacco mosaic. Jour. Dept. Agr. Puerto Rico 17:301-303. 1933.

260 Connecticut E ' xperhment Station Bulletin 457

gram requires years, selection and. although good progress has been
made, we do not know of any investigator who is yet ready to dis-
tribute seed of a resistant variety which he conisders to have suitable
commercial qualities.

At this Station we are attempting to breed a resistant Broadleaf
strain. Starting with a cross between Ambalema and John Williams
Broadleaf, we have back crossed three times on Broadleaf. Many
selections are satisfactorily resistant but they have not been tested
long enough to make sure that they possess proper commercial quali-
ties.

INSECT INVESTIGATIONS DURING 1941
A. W. Morrill, Jr., and D. S. Lacroix *

The cooperative investigations on the control of insect pests of
tobacco in the Connecticut River Valley, which were commenced in
1936 by the Connecticut Experiment Station and the Bureau of En-
tomology and Plant Quarantine of the United States Department of
Agriculture, were continued during 1941.

Various dust mixtures were tested on shade-grown and open held
tobacco in an effort to obtain a simultaneous control of both potato
flea beetle, Epitrix cucumeHs (Harr.), and tobacco thrips. Frankliniel-
la fusca (Hinds). Because of the impossibility of applying sprays
effectively to tobacco late in the season without causing mechanical
injury to the plants, spray materials were not continued in the pro-
gram. Naphthalene and carbon disulfide were tested as soil fumi-
gants for the control of the eastern field wircworm, Limonius agonus
(Say). In addition, the field surveys and general observations of in-
sect conditions on tobacco were continued, as in previous years.

Flea Beetle and Thrips Experiment

Treatments were tested in an attempt to determine a single con-
trol measure for use against both the potato flea beetle and tobacco
thrips.

Although setting 0f (obaeco plants was commended as early as
May L5 this season, winds of 1 5 to 26 miles per hour Mew almost

constantly, preventing dusting until June 12. Thereafter, the treat-
ments were applied at semi-weekly intervals when the weather per
milted until July 11. when heavy showers prevented further dusting

operations. Harvesting of the leaves was completed shortly there-
after. .A total of eight applications was made with each insecticide.
The rate of application of dusts commenced at *i pounds per acre

at the beginning of the season and Increased t<> L2 pounds per acre

as the plants grew. Application- were made by means of rotary

'Bun lu of Entomology and Planl Quarantine and Connecticut Agricultural Bx-

pei mm. ni si.ii ion, i ■ pi 'i h ely.

Tobacco Substation Report for 1941 261

hand-operated dusters in the early morning, usually before 9 A. M.
Standard time, because this period of the day is freest from disturb-
ing wind movements.

Each treatment, as in all similar tests conducted since 1937, was
replicated six times on plots "arranged in a Latin square. Each plot
consisted of one bent of shade-grown tobacco, or one-fortieth acre.
In conformity with the methods used in previous experiments, four
primings of three leaves each were harvested from each of 10 plants,
also chosen at random, in every plot. These leaves were then cured,
fermented and processed in the usual commercial fashion. They were
later examined for evidences of insect injury, which may be either
more or less apparent on the cured leaf than on the green.

Three criteria were used in judging the effectiveness of the treat-
ments, as follows: (A) the populations of flea beetles and thrips as
sampled at intervals during the growing period of the crop, (B) the
percentage of cured leaves showing evidence of feeding injury by
these insects, and (C) the percentage of the total potential wrappers
(four per leaf) showing injury severe enough to damage the value
of the wrappers. Counts of live insects were made on (10) sample
plants chosen at random in each plot immediately before and, again,
24 hours after each application of the insecticides. The percentage
of leaves injured by feeding was determined by examining all leaves
harvested from 10 plants per plot, as previously mentioned, after cur-
ing and processing were completed. In the case of the last-mentioned
criterion, as applied to flea beetle feeding, injury severe enough to
have caused commercial damage when properly located on the leaf
was counted as actual damage when it was not so located. Thus this
criterion is a measurement of the true severity of the injury, but
overstates the commercial importance of such injury in the case of
the flea beetle.

The use of pyrethrum dust gave better control of thrips in terms
of wrappers damaged than did any of the other treatments, except
that it was not significantly better than the treatment in which pyre-
thrum was alternated with cube. There was no significant difference
in the effectiveness of these two treatments and that of the dust mix-
ture containing 1 percent of rotenone in controlling the flea beetles.
All treatments were better than no treatment.

Control Experiments on Open Field Tobacco

A somewhat similar experiment on the control of tobacco thrips
and the potato flea beetle was conducted on plots of open field tobacco
in Buckland, Conn. Each treatment was replicated four times on
plots one-fortieth acre in size that were arranged in two randomized
blocks. The treatments used Consisted of semi-weekly applications of
the dusts shown in Table 1 during the period August 1 to August 16.
These dusts were applied by means of rotary hand-operated dusters

2G2 Connecticut Experiment Station Bulletin 457

at rates of 3 to 30 pounds per acre, depending upon plant size. The
effectiveness of treatments was determined by counts of living ilea
beetles and thrips on 10 plants per plot just before and 24 hours
after each application. The results from this experiment are given
in Table 15. These data show a trend somewhat similar to that of
the results on shade-grown tobacco.

The large decrease in thrips population after the fourth applica-
tion was probably due to heavy thunder storms which came in cloud-
burst proportions, not only washing off many of the thrips but also
spattering the tobacco foliage with mud to suck an extent that it was
difficult to make accurate counts.

The figures accumulated in 1941 on Broadleaf tobacco bear out
the same facts as were found in 1940 on Havana Seed tobacco, i. e.,
pyrethrum does serve to hold thrips in check to a certain degree, but
is not entirely satisfactory.

Pyrethrum dust with a mineral diluent left a white residue on
the tobacco leaves. This had a tendency to wash down towards the
base of the leaves during rains and accumulated there. During dry
weather, the white residue was plainly visible over all the foliage.

Wireworm Control Experiments

On June 6, twelve plots, one-fortieth acre in area (33x33 feet)
were treated with naphthalene at the rate of 800 pounds per acre,
applied in furrows 9 inches deep, approximately 9 inches apart, and
later harrowed. Twelve, others were plowed and harrowed, but were
not treated with naphthalene. Twelve similar plots were treated
with dichloroethyl ether, applied in the setting water at the rate of
100 cc. of ether per gallon, about one-third to one-half pint of the mix-
ture being applied around each plant. This ether was made more solu-
ble in the water by the addition of a commercial cat-ion-active emul-
sifying agent at the rate of 3 parts by volume of the agent to 100 parts
of water. Twelve additional plots were treated with setting water
containing •! grams of para-Aminoacetanalide and 12 were plowed.
harrowed, and set with plain water. The is plots were arranged in
12 randomized blocks. The effectiveness of the treatment was deter-
mined by counting the wireworms obtained in sifting the soil from
six units of I cubic foot each, Located at random in the central por-
tion of each plot. The plots were set with tobacco three days after

treatment with naphthalene, and no difference could be noted in the

vigor of (he plants Oil the treated and untreated plots. However,
the ether <;iiise(| considerable burning of the roots and resetting was

necessa ry.

W hile air temperatures were unseasonably high from early spring,
soil temperatures remained below 7<» until the day of setting, after
which they rose to between 70 and T.v for some days. On dune L8
and July '.• the average reductions in wireworm infestation were de-

Tobacco Substation Report for 194-1

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termined by soil sampling. The results of the samplings taken on
June 18 were not significant. Those of the sampling taken July 9
are shown in Figure 4. While the reduction in wireworm infestation
was barely significantly greater in the plots treated with naphthalene
than in those not treated and somewhat more so in the plots treated
with the ether, the reductions obtained were not sufficient to be of
much practical value to the grower.

In September a new set of 36 plots was arranged in randomized
blocks in a field which had been heavily infested at setting time and
in which 6 resettings were required to get a stand. Twelve plots
were treated with carbon disulfide immediately following the removal
of the tobacco plants after harvest. Twelve plots were plowed to a
depth of about 1 foot and 12 were left untreated, except that all 36
were harrowed before and after the plowing. Temperatures remain-
ed fairly high during the period, the average daily departure being
2.7 Fahrenheit degrees above normal. A reduction in the wireworm
population of 87 percent was obtained in this experiment, which is
considered to be highly significant (Figure 4).

WIREWORM POPULATION BEFORE

(WHITE) 8. AFTER TREATMENT

C BLACK)

AMINO UNTRCATlD

CARBON DISULF.

JUNE 3 AND JULY 9

SEPT. 9 AND 18

Figure 4. Results <>i" treatments applied Eor tin- control of wireworms in
tobacco fields, Buckland, Conn., 1941.

Insect Abundance During 1941

A survey to determine the severity of damage by insects to open
field tobacco in the Connecticut River Valley was conducted during
A.usrust, following (lie method used in previous years. This survey

Tobacco Substation Report for 1941 265

showed that the damage by insect pests was less severe than in 1940
and much less severe than for a number of years preceding. As in
1940, many pests were late in becoming established and some of the
usual pests were not present in any appreciable numbers.

Percentages of leaves showing injury and of those showing com-
mercial damage caused by the insects of major importance were as
follows : Flea beetles, 20 percent and 7.97 percent, respectively ; thrips,
6.54 percent and 1.84 percent; grasshoppers, 7.31 percent and 1.01
percent; and hornworms, 2.66 percent and 0.59 percent.

The Japanese beetle, Popillia japonica (Newm), again was ob-
served feeding on tobacco, but not in such large numbers as in 1939
and 1940. As in previous instances, injury was confined to the tops
of the plant and was very moderate.

The wireworm Limonius agonus (Say), which has been often
reported under the name Limonius ectypus (Say), is frequently a
severe pest of newly set tobacco in the Connecticut River Valley.
In 1941 this insect was an especially serious problem, probably be-
cause of the unusual earliness of the setting of the young plants in the
field. Many fields were attacked so heavily that restocking was nec-
essary five and six times and, since the resetting must be done by hand
rather than by the usual setting machinery, these operations were
unduly expensive. Attack was usually confined to small areas in
certain fields, as is normally the case but, in some instances, whole
fields of fifteen to thirty acres were affected. This latter condition
was seen especially in fields which have been set alternately to both
potatoes and tobacco. Damage by the seed corn maggot, Hylemya
cilicrura (Rond.), was not reported or observed, nor was there any
damage by crane fly larvae or "leather- jackets," which in this region
usually are the larvae of Nephrotoma ferruginea (F.), sodalis
(Loew), or Tipula georgiana (Alex.).

The potato flea beetle, Epitrix cucumeris .(Harr.), and the to-
bacco thrips, F rankliniealla fusca (Hinds), were very scarce follow-
ing heavy rains early in the season, but became almost normally abun-
dant just before harvest. Injury by the flea beetle was approximate-
ly as general as last year, but leaf infestation was not as heavy. On
the other hand injury by thrips was unexpectedly severe on cured
leaves. Whereas excessive feeding by this insect will cause the leaf
to become thin and papery and thus of little value, even moderate
injury causes a white streaking of the leaf. When populations are
small, this streaking is confined to the midrib section and is of little
importance. However, during dry seasons, if no control measures are
applied, the thrips may crowd farther out onto the leaf, and injury
is caused to the wrapper portion of the leaf. This occurred during
the latter part of the 1941 season.

Grasshoppers were rare until near harvest time, when more
feeding than normally was observed in outside rows, probably ow-

2G6 Connecticut Experiment Station Bulletin 457

ing to the drought conditions. The injury in these fields was caused
mainly by the red-legged grasshopper, Melanoplus femur-rubrwm
(DeG.) and. rarely, by the Carolina grasshopper, Dissosteira Carolina
(L.). Cutworms in seedbeds were not reported and few cases of
injury by these insects to the growing plants were observed.

Other usual pests of tobacco in this region, not reported in 1941,
include the tarnished plant bug, Lygus pratensis oblineatus (Say),
the garden springtail, Bourletiella hortensis (Fitch), and the stalk
borer. Papaipema nebris nitela (Guen). The spined stink bug. Eus-
chistus variolarius (Beauv), the spotted cucumber beetle, Diabrotica
duodecimpimctata (F). and the potato aphid, Macrosiphum {Illinoia)
solanifolii (Ashm.), were found doing only very slight damage.

Xo specimens of the tobacco budworm, Heliothis virsescens (F.),
were observed. A few light infestations of the tobacco hornworm,
Protoparce quiiiquemaculata (Haw.), were observed on sun-grown
tobacco before harvest, and several were found on the later suckers.
Although unlikely, it is possible for these worms to overwinter
in this region and to emerge as moths during succeeding years. Such
infestations on suckers are, therefore, potential sources of damage to
subsequent tobacco crops, and the suckers should be carefully destroy-
ed when they appear after harvest. At the same time, growers
should take care not to destroy larvae found crawling in curing sheds
when these larvae are covered with the small, white cocoons of the
parasite, Apanteles congregatus (Say). Contrary to the general con-
ception, these cocoons are not hornworm "eggs" but a potential source
of a hornworm control of considerable value and effectiveness in this
region.

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Connecticut

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