Title: Evaluation of disease control chemicals applied to vegetable crops during the ... growing seasons.
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Title: Evaluation of disease control chemicals applied to vegetable crops during the ... growing seasons.
Series Title: Evaluation of disease control chemicals applied to vegetable crops during the ... growing seasons.
Physical Description: Serial
Language: English
Creator: Thayer, P. L.
Publisher: Everglades Experiment Station.
Place of Publication: Belle Glade, Fla.
Publication Date: 1958-1959
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Bibliographic ID: UF00076885
Volume ID: VID00001
Source Institution: University of Florida
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Resource Identifier: oclc - 166140805

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Everglades Station Mimeo Report 60-8


EVALUATION OF DISEASE CONTROL CHEMICALS APPLIED TO
VEGETABLE CROPS DURING THE 1958-59 GROWING SEASONS

P. L. Thayer


This report was prepared for reference by research per-
sonnel and industry. The data presented do not consti-
tute recommendation of any fungicide, bactericide or
soil fumigant.


Agrimycin 100

Amobam

Captan

Chloranil

Chloropicrin

Cyprex

D 113

Dichlone

Dyrene

Ferbam

GC2466


GC189


Kildrench No. 4


Maneb

Methylbromi.de

Miller 658

Mylone 85H1


Nabac


MATERIALS USED

15% Streptomycin, 1.5% Terramycin

42% Diamonium ethylene bisdithiocarbamate

50% N-Trichloromethylthiotetrahbdro-Phthalimide

48% Tetrachloroquinone

Trichloronitromethane

70% Dodecylguanidine acetate

Experimental material; Chemagro Corp.

50% 2,3-Dichloro-l, 4-napthoquinone

50% 2,4-Dichloro-6-(O-chloroanilino) triazine
76% Ferric dimethyl dithiocarbamate

Experimental material; General Chemical Divisiol
Allied Chemical Corp.

Experimental material; General Chemical Divisiol
Allied Chemical Corp.

16% DD, 21% allyl alcohol, 33% formaldehyde,
6% nitrogen.

70% Manganese ethylene bisdithiocarbamate



95% copper zinc chromate complex (29. 4i6 o4

85% 3,5-dimethyl-l, 3,5, 2H-tetrabydroth a azine
2-thione

25% 2,2-methlenebis(3,4,6-trichlorophenol) PAR.


n,


n,


December 16, 1959









Nabam 22% Disodium ethylene bisdithiocarbamate

Nemagon 50% 1,2-Dibromo-3-chloropropane

Cmadine-copper 50% copper salt of 2-pyridenethione 1-oxide

Omadine-Iron Ferric salt of 2-pyridenethione 1-oxide

Panogen Soil Drench 3.5% Methylmercury hydroxide

PCNB 75% Pentachloronitrobenzene

SD-4741 Experimental material, Shell Development Co.

Thiram 65% Tetramethylthiuram disulfide

TBCS Tribasic copper sulfate, 53% copper

Vapam Sodium N-methyl dithiocarbamate

Zineb 65% zinc ethylene bisdithiocarbamate

Ziram 76% zinc dimethyl dithiocarbamate

28-720 Experimental material, American Cyanamid Co.

Celery Seed-bed

Fumigation Trial Several soil fumigants were tested for disease and weed
control on a seed-bed at A. Duda & Sons Farm, Belle Glade. This test was in
cooperation with Dr. J. R. Orsenigo, whose report of the weed control data
is recorded elsewhere.

A random block experimental design was used with three replications on
a single 4 ft. by 300 ft. seedbed. Each plot was the width of the seedbed
(4 ft.) by 6 ft. in length, which allowed for approximately 15 ft. of
untreated area on each end of the seedbed. Fumigants were applied two weeks
before seeding. All the materials except methyl-bromide and chloropicrin
were mixed with water and applied with a hand sprayer over the soil surface
at a rate of 100 gallons per acre. After treatment all plots except those
receiving methyl-bromide were drenched with inch of water. Methyl-bromide
was metered out of one pound cans over plots under plastic covers. The
covers were sealed around the edges to prevent loss of the gas, and were
removed 48 hours after treatment. Chloropicrin was applied with a hand
injector to a depth of six inches at the intersections of 10 inch squares.

Results are presented in Table 1. Plant stand was not affected by any
of the treatments. This indicates 1) there was no severe toxicity to the
plants by the chemicals; and 2) no great loss of plants occurred because
of damping-off. However, a count of diseased plants taken three weeks after
seeding revealed some damp-off control by certain treatments.








-3-
Table 1. Evaluation of fumigants for celery seedbeds.


Application Rate; Dry weight
per acre active Seedlings Plants damped-off of 100 plants
Material material per sq. ft. per square foot in grams

1. Kildrench 76 gal. 110 8.3 19
2. Kildrench 152 gal. 127 1.8 18
3. Shell SD 4741 21 gal. 124 4.8 17
4. Shell SE 4741 42 gal. 123 2.5 17
5. Methylbromide 425 lb. 135 3.2 18
6. Methylbromide 850 lb. 114 2.5 19
7. Chloropicrin 36 gal. 127 8.2 22
8. Chloropicrin 72 gal. 123 9.3 24
9. Check ---- 131 9.3 18
10. Mylone 85 w 200 lb. 127 7.5 18
11. Mylone 85 w 300 lb. 117 3.3 18
12. Nemagon 5 gal. 119 3.5 20
13. Nemagon 10 gal. 122 3.2 20
14. Vapam 60 gal. 102 3.2 24
15. Vapam 100 gal. 130 4.7 16

LSD at 0.05 NS 4.9 NS

Spray Trials Two spray trials were undertaken on celery seedbeds. The first
was on the Wedgewroth farm and was an evaluation of the dithiocarbamates,
chloronil, and tribasic copper sulfate for control of seedbed foliage diseases.
The second was on the Senter farm and was an evaluation of Dyrene in various
combinations with copper and streptomycin for celery seedbed disease control.

Each experiment utilized two, 4 x 300 ft. seedbeds. There were four repli-
cations, two on each seedbed, of 4 x 10 ft. plots arranged in a random block
design. Celery variety Utah 52-70 was used. Materials were applied at four
or five-day intervals at a rate of 10 gal. per seedbed. Parathion was applied
separately at nine-day intervals for insect control. Materials were applied
with a hand sprayer in the first test at approximately 20 Ib. pressure. In
the second test a power sprayer, connected to a hand boom by a 50 ft. section
of hose, was used at 300 to 400 lb. pressure.

Results of the first test are in Table 2. When stand counts were taken
August 15 the check plots had a greater number of plants than all other treat-
ments except the tribasic copper sulfate and the zineb + thiram plots. By
September 4 the number of plants in the check plots and the tribasic copper
sulfate plots were substantially reduced while the plots receiving zineb +
thiram had no stand reduction. The amount of early blight in these plots
is related to the stand reduction as can be seen by the disease ratings.
All of the dithiocarbamates did an acceptable Job of controlling early
blight. In addition to controlling early blight thiram controlled
Rhizoctonia rot. Chloronil was also effective in controlling both early
blight and Rhizoctonia rot. Maneb and the tank mix nabam + MnSO caused
some stunting and chlorosis of small plants. Amobam plus calcium hypo-
chlorite produced necrotic lesions on the celery plants.










Table 2. Effectiveness of spray treatments on celery in seedbeds for control
of early blight (Cercospora apii Fres.) and Rhizoctonia rot
(Rhizoctonia solani Kuhn) Summer 1958


Rate of No. Plants Early Blight Rhizoctonia
Application per sq. ft. Rating!- Rot Rating
Treatments lbs./l00 gal. Aug. 15 Sept. 4 Aug. 15 Sept. 4 Sept. 4

1. maneb 2-100 29 25 1.0 1.7 2.7
2. zineb 2-100 29 24 1.0 1.5 2.7
3. ziram 2-100 25 26 1.0 2.4 2.7
4. ferbam 2-100 28 27 1.0 2.2 2.5
5. thiram 2-100 26 26 1.0 2.4 2.0
6. amobam + calcium 1 qt-100
hypochlorite + 1i-100 26 24 1.0 2 2.7 3 0
7. nabam + MnSO4 2 qt-100,
3/4 -100 25 28 1.0 2.0 3.0
8. tribasic copper sulfate 4-100 33' 28 1.5 5.0 3.2
9. chloronil 4-100 27 26 1.0 1.7 1.5
10. zineb + thiram 2-100, 1-100 32 34 1.0 1.6 2.5
11. Check 36 24 3.2 9.2 4.2

LSD 0.05 6 4 0.7 2.0


l/ Horsfall and Barratt's disease rating
diseased.


system used:


1 = no disease, 12 = 100%


Results of the second test are recorded in Table 3. Plants in these seedbeds
were in a thinly populated stand which allowed for maximum air circulation and
probably accounts for the perfect control of early blight obtained with Dyrene,
maneb and zineb + thiram. Dyrene did not cause any detectable toxicity to the
plants even when combined with tribasic copper sulfate and/or streptomycin.
Copper sulfate was not as effective as the dithiocarbamates or Dyrene in
controlling early blight.










-5-

Table 3. Effectiveness of spray treatments on celery in seedbeds for control
of early blight (Cercospora apii Fres.) Summer 1959.


Rate of Application
in lbs. per 100 gal. Early Blight Rating/
Treatments or parts per million Sept. 1 Sept. 8

1. maneb + streptomycin 1--100, 50 ppm 1.0 1.0

2. zineb + thiram +
Streptomycin 2-100, 11-100, 50 ppm 1.0 1.0

3. Dyrene 1-100 1.0 1.0

4. Dyrene + streptomycin 1--100, 25 ppm 1.0 1.0

5. Dyrene + streptomycin 1--100, 50 ppm 1.0 1.0

6. tribasic copper sulfate 4-100 2.2 2.2

7. tribasic copper sulfate +
streptomycin 4-100, 50 ppm 2.0 2.2

8. streptomycin 25 ppm 4.7 5.7

9. streptomycin 50 ppm 4.7 5.7

10. Dyrene + tribasic copper
sulfate 1-100, 4-100 1.0 1.2

11. Dyrene + tribasic copper
sulfate + streptomycin 1-100, 4-100, 25 ppm 1.0 1.0

12. Dyrene + tribasic copper
sulfate + streptomycin 1-100, 4-100, 50 ppm 1.0 1.0

13. Dyrene + tribasic copper
sulfate + streptomycin 1--1-00, 4-100, 50 ppm 1.0 1.0

14. Check 5.7 6.5

LSD at 0.05 1.6 0.4


Horsfall and Barratts' disease rating system used:
12 = 100% diseased.


1 = no disease,


I






Field Celery

The two spray trials on field celery were located on the Experiment Station.
Plants were sprayed with a small power sprayer at 300 to 400 lbs. pressure.
Gallonage per acre varied from 50 to 150 with two nozzles per row on young
celery, increasing to six nozzles on mature plants. Spray materials were
applied at four or five-day intervals. Celery variety Utah 52-70 was used
in a random block design with five replications of 25 ft. each. Plots were
single row.

The first test compared various concentrations of Dyrene and tribasic
copper sulfate alone and in combinations for control of early blight, Results
are presented in Table 4. Since Dyrene is an expensive material this experi-
ment was designed to determine the minimal dosage necessary for good disease
control. Dyrene and tribasic copper sulfate had previously been shown to be
additive in their control of celery early blight Thus a mixture of the two
permits use of less Dyrene as well as gaining some control of bacterial blight
from the copper. The additive effect was demonstrated in this experiment but
not at all concentrations. Dyrene at 1-100 was sufficiently effective in con-
trolling early blight that the addition of copper did not improve control. The
additive effect was in evidence at 1-100 Dyrene with either 2-100 or 4-100
copper. Dyrene --100 plus copper at 4-100 was additive but not Dyrene j-100
plus copper at 2-100. Under the conditions of light bacterial blight infesta-
tion of this test copper reduced the disease severity. It is doubtful that
any additive effect with Dyrene occurs in bacterial blight control. The
minimum safe concentration for the combination spray is Dyrene at 1-100 and
tribasic copper sulfate at 4-100. If Dyrene is used alone for early blight
the dosage should be raised to 1--100.

Table 4. Effect of spraying various concentrations of Dyrene and tribasic
copper sulfate (TBCS) alone and in combination on early blight
(Cercospora apii) and bacterial blight (Pseudomonas apii Jagger)
Fall 1958.

Rate of appli- Early bligt Bacterial blight Yield in
Treatment cation Ibs. Ratings- ratings Ibs. per 25
per 100 gal. Nov.17 Dec. 1 Oct. 14 Dec. 1 foot plot

1. Dyrene -100 3.8 4.5 3.1 57
2. Dyrene 1-100 2.7 3.4 3.2 3.0 65
3. Dyrene 1-100 2.2 2.7 3.3 2.8 67
4. TBCS 2-100 5.7 5.9 3.0 43
5. TBCS 4-100 5.3 6.2 2.5 42
6. Dyrene + TBCS --100, 2-100 3.5 4.0 2.4 2.4 66
7. Dyrene + TBCS --100, 4-100 3.0 3.5 2.2 1.7 72
8. Dyrene + TBCS 1-100, 2-100 2.6 2.7 2.3 2.4 76
9. Dyrene + TBCS 1-100, 4-100 2.3 2.6 2.3 2.1 78
10. Dyrene + TBCS 1-100, 2-100 2.2 2.2 2.0 2.3 72
11. Dyrene + TBCS 1--100, 4-100 1.8 2.3 1.8 1.7 76
12. Check --- 6.8 7.2 3.8 19
LSD at 0.05 00.5 0.6 0.4 0.5 8
1/ Horsfall and Barratt's disease rating system used: 1 = no disease and
12 = 100q diseased.







The second fungicide spray trial on field celery was a comparison of
new materials with those now in use for disease control. In addition to
this, a sticker (California Spray-Chemical Corp. ML104) was used with three
materials to test its effect on disease control. Results of this test are
presented in Table 5. Dyrene, Nabam plus zinc sulfate, and maneb were the
more effective materials used for early blight control. Miller 658 (copper
zinc chromate complex) was as effective in combination with Dyrene as tri-
basic copper sulfate. Apparently the source of neutral copper is not
important in the additive effect of copper-Dyrene mixtures for early blight
control. Use of a sticker with nabam plus zinc sulfate, captain, and
dichlone did not improve disease control. Neither captain nor dichlone
gave satisfactory early blight control. None of the new materials were
effective in controlling early blight.


Table 5. Effect of various materials sprayed on field celery
+ early blight (Cercospora apii) Spring 1959


on control of


Rate of appli-
cation in lbs. Yield in lbs.
per 100 gal. or Early Blight Ratings-' per 25 ft.
Treatment parts per million Mar. 24 Apr. 4 Apr. 15 plot
1. Dyrene + tri-
basic copper
sulfate 1-100, 4-100 1.0 1.4 1.8 107
2. Dyrene+Miller 658 1-100, 2-100 1.3 1.7 2.0 102
3. Dyrene+Strepto-
mycin 1-100, 100 ppm 1.2 1.7 2.5 118
4. nabam + ZnSO4 2.qt.-100, 3/4-100 1.6 2.1 2.9 99
5. nabam + ZnSO4 + 2 qt-100, 3/4-100,
ML104 I pt-100 1.5 2.7 3.2 104
6. Captan 50W 2-100 2.2 4.2 4.8 90
7. Captan 50W +
ML104 2-100, pt-100 2.2 4.2 5.2 87
8. dichlone 50W 2-100 1.6 3.1 3.9 113
9. dichlone 50W +
ML104 2-100, pt-l00 2.0 3.1 4.0 103
10. maneb 1-100 1.5 2.3 3.0 104
11. Cyprex 1-100 2.3 4.8 5.6 60
12. 28-720 1-100 2.8 5.0 5.8 73
13. 28-720 2-100 2.2 4.8 5.6 81
14. GC 2466 2-100 1.8 3.6 4.4 94
15. GC 1189 2-100 3.2 6.4 6.6 69
16. Check --- 3.1 6.4 6.8 65
LSD at 0.05 0.4 0.8 0.7 14


1 = no disease and


l/ Horsfall and Barratt's disease rating system used:
12 = 100% diseased.





-8-


Cabbage

Several new materials were compared with those currently in use on
cabbage. Spray materials were applied on a weekly schedule using a small
power sprayer at 300 to 400 lb. pressure. Two nozzles per row were used
on young cabbage and increased to six nozzles as the plants approached
maturity. Gallonage ranged from 50 gal./acre to 150 gal./acre. The
cabbage variety used was Copenhagen Market. Single row plots were direct
seeded in a random block design with five 25 ft. replications.

Results are presented in Table 6. Disease incidence during the course
of this experiment was for all practical purposes non-existent, consequently
only toxicity and yield data were obtained. Streptomycin caused chlorosis
of the cabbage plants but it was not serious enough to reduce the yield.
Amobam plus calcium hypochlorite caused necrotic spotting on the plants
which made them unmarketable. However, there was no reduction in the
weight of heads. Nabac at 2 lbs./l00 gal. visually was not toxic to the
plants but reduced the yield.

Table 6. Effect of several foliar spray materials on yield of cabbage.
Fall 1958.


Rate of Application
in lbs. per 100 gal. Yield in lbs.
Treatment or parts per million per 25 ft. plot
1. chloronil 4-100 57
2. Captan 2-100 51
3. Phygon XL 1-100 54
4. Dyrene 1l-100 58
5. amobam + calcium hypochlorite 1 qt-100, 1-100 51
6. zineb 2-100 59
7. tribasic copper sulfate 4-100 54
8. GC 2466 2-100 50
9. Nabac 1-100 51
10. Nabac 2-100 46
11. Dyrene + tribasic copper sulfate 1-100, 4-100 56
12. streptomycin + tribasic copper
sulfate 100 ppm, 4-100 55
13. streptomycin 100 ppm 52
14. Omadene (ferric salt) 2-100 53
15. Check 53
LSD at 0.05 6









Pepper


Several materials were tested for control of bacterial spot of pepper.
They were applied with a plot sprayer at 300 lbs. pressure and 50 to 150
gallons per acre. Plants were sprayed at five-day intervals beginning
November 17, 1958. California Wonder pepper variety was used. Peppers
were direct seeded using a Plantet Jr. hand seeder. Experimental design
was a random block with five 25-foot single-row replications. Alternate
rows were left as buffers. The buffer rows were inoculated during the
week of November 23, with Xanthomonas vesicatoria in a water suspension
sprayed on the plants with a hand sprayer.

Yield data were not taken because an infestation of cucumber mosaic
virus prevented fruit set to a large extent. Disease ratings are pre-
sented in Table 7. None of the treatments used was effective in con-
trolling bacterial spot, although streptomycin did delay development
of the disease for a short time. The combination of Dyrene and TBCS
caused stunting and chlorosis of the pepper plants.

Table 7. Effect of various materials on development of bacterial spot
on pepper.


Rate of Disease Rating
Treatments Application Dec. 2 Dec. 9 Dec. 15 Dec. 23
1. streptomycin 100 ppm 2.5 2.4 3.1 4.6
2. TBCS 4-100 2.9 3.1 3.5 5.4
3. Nabac 1-100 3.3 3.4 3.4 5.2
4. Nabac 2-100 2.9 3.1 3.1 5.0
5, Omadine copper 2-100 2.8 3.5 3.7 5.2
6. streptomycin + TBCS 100 ppm, 4-100 2.7 2.7 2.8 4.8
7. Nabac + TBCS 1-100, 4-100 3.4 3.7 3.4 5.2
8. Nabac + TBCS 2-100, 4-100 3.1 3.3 3.1 5.2
9. Dyrene + TBCS 1-100, 4-100 3.6 3.7 4.2 5.8
10. Check ---- 3.1 3.3 3.4 5.4
LSD at 0.05 0.5 0.7 NS NS


no disease,


1/ Horsfall and Barratt's disease rating system used: 1 =
12 = 100% diseased.





-10-


Beans

Loss of plants from damping-off has been reduced by use of chemicals
applied as drenches in the furrow at planting time. Pentachloronitro-
benzene (PCNB) applied in this manner has been reported to control
Rhizoctonia stem canker and damping-off in several crops. In bean
plantings where Pythium species as well as Rhizoctonia solani contri-
bute to the damping-off problem, the addition of Captan to PCNB
sometimes increases disease control. In the relatively few cases
that yield data were recorded, in the furrow application of fungicides
have not increased bean yields in Florida. Work reported here was
undertaken to compare new fungicides with the standards for control
of Rhizoctonia and Pythium damping-off of snap beans and to determine
their effect on yields.

All plots were located on sandy soil at Plantation Field Labora-
tory in an area previously utilized for soil fungicide testing and
known to have had high populations of both Rhizoctonia and Pythium.
Uniformity trials before each experiment indicated that there was no
carry-over of fungicides from previous plots in sufficient amounts to
affect disease development in current plots. Single row plots were
used on beds of two rows each when nonvolatile materials were tested
and one row per bed when volatile materials were tested. Fertilizer
applications were made as needed and sprays were applied for control
of foliar disease and insect pests. The bean variety was Contender,
planted at two-inch intervals in the row.

Table 8. Effect of several fungicides applied in the furrow at planting
time on damping-off and yield of snap beans, fall 1958.


Application
Rate per
atcre -


Stand count2-
Ave. Range


Percent Post
Emergence damp'off
Ave. Range


Yield lbs.per
25' plot
Ave. Range


1. PCNB & Captan
2. D-113
3. Chloranil
4. Chloranil
5. Dyrene
6. PCNB & dichlone
7. PCNB & Phygon
8. Nabac
9. amobam
10. GC 2466
11. GC 1189
12. Check


4 lb.-4 lb. 120 114-128
5 lb. 34 26-46
8 lb.-4 lb. 133 117-131


8 Ib.
5 lb.


133 121-141 20
134 128-136 28


4 lb.-4 lb. 121
4 lb.-4 lb. 123
5 lb. 130
2 qt. 114
5 Ib. 96
5 lb. 124
126


LSD at 0.05
Coefficient of variability


115-129 48
114-134 34
117-138 28
107-126 28
65-108 52
113-138 61
119-135 30


7.2


31%


14-68 2.4 1.2-3.0
22-41 1.6 1.1-1.7
6-37 4.9 2.5-7.8
12-31 4.2 2.8-5.4
18-41 4.4 2.0-6.8
33-75 2.9 0.6-5.8
3-54 3.3 1.8-5.4
15-37 4.1 1.6-5.8
12-51 4.5 2.8-7.9
26-75 3.6 1.8.7.3
47-73 2.6 0.9-5.1
18-40 4.1 2.1-6.3
2.0
45%


/ Based on 309 of each acre treated.
SNumber of plants emergent from 150 seed planted.


Treatment


-- --


acre






-11-


Two similar experiments were designed to test fungicides applied in the
furrow at planting time. A random block design with 25-foot plots replicated
five times was used for both experiments. In the first experiment the test
materials were applied with a sprinkling can as a drench over the seed in the
opened furrow in 40 gallons of water per acre. One mixing of each material
was made for all five replicates. Results of this trial are presented in
Table 8.

In the second experiment refinements in the application of the fungicides
were made in an attempt to reduce variability. Materials were measured and
mixed separately for each replication of each treatment. They were then
applied with a hand sprayer in the following manner: two passes were made
over bean seed in the opened furrow with the spray, then spray was applied
to the soil as it was pulled in over the furrow, and finally two or three
passes were made over the closed furrow. The fungicides were applied in
20 gallons of water per acre. Results of this experiment are reported in
Table 9.

Table 9. Effect of several fungicides applied in the furrow at planting
time on damping-off and yield of snap beans, spring 1959.

1/ Percent Post
Application / Stand count- Emergence Yield lbs.
Treatment Rate per acre! Ave. Range Damping-off per 25' plot
Ave. Range Ave. Range
1. PCNB & Captan 4 lb.- 4 lb. 128 121-142 45 26-67 3.8 2.8-5.2
2. PCNB & Captan 8 lb.- 8 lb. 111 96-129 54 13-75 2.7 1.8-3.8
3. D-113 3 lb. 118 110-129 26 5-42 4.4 3.3-5.6
4. D-113 & Captan 3 1b.-4 lb. 123 113-138 20 5-27 4.9 4.3-6.1
5. Chloranil & Captan 4 lb.-4 lb. 128 102-144 17 7-31 4.7 3.5-6.5
6. Chloranil & Captan 8 1b.-8 lb. 132 121-140 19 1-28 4.1 1.3-6.2
7. Chloranil 8 Ib. 133 123-142 19 4-37 5.2 3.6-6.9
8. Panogen Soil drench 1 gal. 4 0-10 -
9. GC 2466 5 lb. 109 68-131 37 20-67 3.8 2.7-5.7
o1. Gc 1189 5 lb. 102 51-139 44 13-67 3.2 1.9-3.8
11. SD 4741 & PCNB 1 gal.-4 lb. 135 128-140 11 2-25 4.8 2.8-6.2
12. Check -- 104 78-142 32 12-50 3.9 3.2-5.1

LSD at 0.05 12 17 1.4
Coefficient of variability 13% 46% 28%

1/ Based on 30% of each acre treated.
2/ Number of plants emerged from 150 seed planted.






-12-


Table 10. Effect of chloropicrin and vapam on damping-off and yield of snap
beans, fall, 1958.


Percent post
Application 1/ Stand count/ emergence Yield lbs. per
Treatment Rate per acre- Ave. Range damping-off 10' plot
Ave. Range Ave. Range
1. Chloropicrin 3 gallon 54 50-59 2.8 0-7 3.2 2.1-4.0
2. Chloropicrin 6 gallon 52 47-55 12.0 5-19 0.7 0-1.6
3. Chloropicrin 12 gallon 52 46-57 15.5 6-24 0.3 0-0.7
4. Vapam 5 gallon 52 51-55 18.5 8-33 3.2 2.7-3.5
5. Vapam 10 gallon 54 52-56 9.7 0-22 4.2 3.6-4.7
6. Check -- 47 40-54 30.7 29-32 3.1 2.3-4.2

LSD at 0.05 NS 12.6 1.2
Coefficient of Variability 8% 24% 27%

I/ Based on 30% of each acre treated.
2/ Number of plants emergent from 60 seed planted.


In both experiments isolations from diseased plants revealed largely
Phthium species causing damping-off.

In the first test apparently little pre-emergence damping-off occurred
since no increase in stand over the check plots could be detected. In the
second test several treatments increased stand, presumably because of pre-
emergence damping-off control. The material, D-113, was toxic to the bean
plants in the first test at 5 lb. per acre but not detectably toxic in the
second test at 3 lb. per acre. No claim can be made for control of post-
emergence damping-off or increase in yield for any of the fungicides used
in these two tests. The coefficients of variability were extremely high
for damping-off and yields in both tests.

In a third experiment the volatile fungicides, chloropicrin and vapam
were tested for control of bean damping-off. This experiment was preliminary
and only 10 foot plots were used with four replications. Chloropicrin was
applied with a hand injector at 10 inch intervals in the row. Vapam was
mixed with water and applied as a drench with a sprinkling can at the rate
of 40 gallons per acre. Bean seed was planted 14 days after treatment.
Results are reported in Table 10. Neither of the materials affected plant
stand although chloropicrin at 6 and 12 gallons per acre caused stunting and
chlorosis of the beans which was evident throughout the growth period of the
plants. Chloropicrin reduced post-emergence damping-off without detectable
toxicity at the three-gallon rate, but there was no increase in yield over
the untreated plots. Vapam apparently reduced post-emergence damping-off
although the range in percent damping-off was too great within the treatment
to draw definite conclusions. The coefficients of variability for damping-
off and yields were also high in this experiment.

In two of the three tests damping-off was controlled to some extent by
use of chemical treatments. In the test recorded in Table 9 pre-emergence
damping-off was reduced by several treatments as is evidenced through











-13-

increased stands. In the test recorded in Table 10, chloropicrin reduced
post-emergence damping-off. Despite disease control yields were not affected
by any of the treatments. Lack of yield response can no doubt be partially
explained by a tendency of individual bean plants to increase production of
fruit as the stand is decreased. This is illustrated by a stand count at
harvest in the chloropicrin-vapam experiment. Eighty-three percent of the
seeds planted were represented by plants in the treatment which received
three gallons per acre chloropicrin compared to 54 percent in the untreated
check, yet the yield of beans in these two plots was the same.

The coefficients of variability for damping-off and yields are too high
in all three of these tests. In the first two this can be largely attributed
to unequal distribution of the disease inciting fungi plus ineffective control
by the non-volatile fungicides. Of course unequal distribution of the fungi
is a factor in the third test also but despite this and the fact that smaller
plots and fewer replications were used, better disease control with chloro-
picrin reduced the coefficients of variability to some degree.




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