Results of laboratory and field tests with DDT against the pea weevil

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Material Information

Title:
Results of laboratory and field tests with DDT against the pea weevil
Physical Description:
10 p. : ; 27 cm.
Language:
English
Creator:
Brindley, T.A ( Tom Albert ), 1906-
Schopp, Ralph
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Dept. of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

Subjects

Subjects / Keywords:
DDT (Insecticide) -- Testing   ( lcsh )
Pea-weevil -- Control   ( lcsh )

Notes

Additional Physical Form:
Also available in electronic format.
General Note:
Caption title.
General Note:
"E-668."
General Note:
"August 1945."
Statement of Responsibility:
by Tom A. Bradley and Ralph Schopp.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030290523
oclc - 779925129
System ID:
AA00026039:00001

Full Text

August 1945 S E-668

UnJteL States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine

RESULTS OF LABORATORY AND FIELD] TESTS WITH DDT AGAINST THE PEA WEEVIL l/

13 Tom A. Br-indley and Ralph Schopp, Division of Truck Crop and Garden Insect Investigations

As the result of preliminary tests with DIY against the pea weevil
6hu plsorum (L.)) during 1944, it was reported _/ that this insecticide did not give promise of being a prospective remedy for the insect.
The results obtained, however, in the more recent laboratory and field
tests discussed in this circular indicate that DI has considerable promise as a pea weevil insecticide. This brief discussion of the tests performed during the entire season at Moscow, Idaho, and vicinity has been prepared
for early distribution to interested persons owing to the keen interest displied in DDT as a possible substitute for the rotenone-containing insecticides used ordinarily for the control of the pea weevil but which have been
rendered scarce by wartime conditions.

Laboratory Experiments

Methods. The technique in the laboratory tests was as follows: Five
replicates were treated for each of the materials tested. Fifty weevils
were dusted for each material in each replicate, making a total of 250
weevils treated with each material. The insects were treated under a darkened bell-jar dusting chamber under five pounds air pressure and retained in
the bell jar five to seven minutes to allow the dust to settle. After exposure the treated weevils were transferred to clean cages to remove them from contact with the insecticide being tested. Immediately prior to and following the treatment, the insects were kept under constant temperature
of 860 F. and 65 percent relative humidity, with one exception where a lower temperature was used for comparison, which is described in the discussion
of that experiment. The insects in each replicate were left under observation for ten days. At the end of this period all weevils able to fly or
walk were considered to be living and the others were counted as dead.


l/ I, cooperation with the Agricultural Experiment Stations of Idaho
and Wash ington.

2/ S'whopp, Ralph, and Brindley, Tom A. Tests with DDT against the pea
weevil. lJour. Econ. Ent. 37: 150-151. 1944.








~ 1- 1945







Results: periment In 1 this test pea weevils were exposed
to dosages of a 1O percent ID in ure in py. ophyllite. The dosages
were varied from 0. t ro to determine if increased dosages
would naturally th kill obtained. A study of the data in
... .ze th ~. a~d varied from 69.35 percent with a
dosage of 0.2 ge to 9(o percent with a dosage of 0.5 grams. A dosage ol D.> gr rho boratory dusting apparatus is equivalent
to an appi~ ation a pn per acre on a field basis.

Experiment I. The llence of temperature on the toxicity of DTi to tLe pa weevi was tested in this experiment. Duplicate
series .~ ta eeils collected from the same source
wre eoe& to a os; a 2 each of the following insecticides for five minutes: ( A dust mixture containing 5 percent of nT, with pyrophillite as t dI .luent. (2) A dust mixture containing a combination of 5 percent of DDT plus 0.25 percent of rotenone.
(3) A duet mixture containing 025 percent of rotenone. After treat.nt one series of we(5--1 lo held for 10 days exposed to each isecticie at a constant temperate e of 860 F. and the other series t a temperature of 70' F. e h-vtdity in all series was held constant at appoximately 65 percent.

The result, of this test e summarized in table 2. These data
indicate that dust mixture containing 5 percent of DDT, whether used alc.e xe in ombination with rotenone, was mre effective in killing the pe ue*.I at 700 F. than at 860 F. When used alone, the kill was approximately 60 percent greater at 700 F. than at 860 F. L combination with : parent of rotenone, the kill was approximately 22 percent great r at 700 than at 860 F. The reason far the apparently increased taxicity of DDTI to the pea weevil at the lower temperature has not been determined, and this point needs further investigation before definite conclusions can be drawn.

This experiment also :iii.ated that the kill obtained with a
combination containing rotene was increased slightly by the additon of DIDT at the lower temperature level but the reverse was true a h higher temperature tested.

-aie ot III. This series of tests was made to determine if the length of exposure to DiT would increase the kill obtained. The weevils were exposed to a uniform dosage of 0.3 grams of a 5 percent mixture of DT and pyrophyllite in one series and to a 10 percent mixture of DjL. in another series. After exposure the weevils were held in the chamber in the exposure cages from 5 to 40 minutes before they were transferred to clean cages. The results of this experiment are given in table 3.

A study of these data shws an increase in effectiveness with an increase in the length of exposure to the dust. In the case of the 5 percent mixture of DDT and pyrophyllite, the kill increased from 30.67 percent after 5 minutes exposure, to 63.01 percent after
0 minutes exposure.- With the 10 percent dilution, the kill increased





-3

from 419.60 to 78.00 percent. The difference in kill between consecutive periods of exposure was not statistically significant, but between 5 and 20 minutes, 10 and 40 minutes, and 5 and 40 minutes,. the differences were highly significant.

Field Experiments

The material used in the field plots was a 10 percent dust mixture of DDT in pyrophyllite supplied by the Bureau of Entomology and Plant Quarantine from material purchased in 19144. No laboratory experiments have been made with this lot of material. The dust mixture used in these tests was prepared by diluting the 10 percent DDT] dust mixture with pyrophyllite to contain 5 percent of DMrI. The cube dust mixture used was a commercial brand labeled to contain 0.75 percent of rotenone. The dust mixture containing 5 percent of D~lL was applied at the rate of 30 pounds per acre and the rot enone -containing dust mixture was applied at the rate of 20 pounds per acre.

















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-6

Table 3. Results of laboratory experiments with DI against the pea weevil,
showing influence of length of exposiwe.


: Total : Weevils
Material and WervfK ) Total : weevils, : dead,
expaAi_-we tima* : numb-or_ :3/16:3!17:3/21: number : number : percent

DDT 50 5 min. Living 35 39 29 34 28 165
Dead 10 8 21 16 18 73 238 30.7

DT 5%, 10 min. Living 49 25 28 40 41 183
Dead 1 24 18 10 7 60 243 24.7

DOT 5%, 20 mn. Living 34 23 31 32 23 143
Dead 16 27 20 19 27 109 252 43.3

5r 5%, 40 min. Living 26 33 10 3 19 91
Dead 24 17 39 44 31 155 246 63.0

DI il0%, 5 min. Living 31 34 31 6 23 125
Dead 17 16 19 44 27 123 248 49.6

DD 10%,, 10 mn. Living 30 3 3 13 18 67
Dead 18 48 48 37 32 183 250 73.2

DIT 10%, 20 min. Living 11 23 14 1 2 51
Dead 38 26 36 50 48 198 249 79.5

DI 0, 40 min. Living 23 7 12 9 4 55
Dead 27 43 38 41 46 195 250 78.0

Check Living 48 49 46 49 40 232
Dead 2 2 4 1 10 19 251 7.6


* Insects allowed to remain after dusting in the chamber for different
periods of time before being transferred to observation cages. Pyrophyllite
was used as diluent.





-7

Each of the plots used in this experiment were 1.10 of an acre
in size. They were arranged singly along the edges of 6 pea fields in order to insure the presence of a high pea weevil population and to benefit from a mirmum of interplot movement of the weevils. Each of the insecticlIe- was arplied with a power duster to 21 of these plots. The treatment order was according to a randomized block plan. Two 25-sweep collections with an insect net were taken on each plot immediate ,ef7z w- a 't aL7,. 48-hour intervals after dusting. The reults of this experimennt, as given in table 4, indicate that on the basis of reduction of pea weevil populations there was very little difference in the degree of control obtained with a dust mixture containing 5 percent of DDT applied at a rate of 30 pounds per acre as compared with a d-.'t mixture containing 0.75 percent of rotenone applied at a rate of 20 pounds per acre.

At harvest, during the dry pea stage, an examination of samples of peas from 7 comparable plots where each of the insecticides had been applied indicated that, judging from the samples examined, 1.8 percent of the peas were infested by the pea weevil in the plots receiving the DI insecticides while 2.7 percent were infested in the plots where the rotenone containing insecticides were used. Two samples of 1000 peas each were examined from each plot.


Table 4. Results of dust applications on pea weevil populations in
1.0 acre plots on edges of pea fields, June 18 to 29,
1944, temperature 700 -81 .



Total weevils Reduction in
collection in population of
Insecticide 21 plots weevil adults

Number Percent
Cube
(0.75 percent Before dusting 1134
rotenone) After 24 hours 16 98.8
After 48 hours 24 98.2

DDT
(5 percent) Before dusting 1176
After 24 hours 20 98.3
After 48 hours 9 99.2






-8


Tolerance of Pea Plants of DDTI

Te~lqe Experiments have been made to determine whether pea
plants might be affected by applications of M.I Germination of seeds and growth off plants were recorded when the seeds were rolled In DDT prior to planting and 4hen the DDTI was placed in the seed furrow at planting time. Plants dusted with DDT were also tested as to growth and observations made f'or Injury.

Alaska peas were used in an experiment with six randomized blocks
using plots consisting of 10 feet of row. The data on this experiment have been analyzed statistically and are summarized and presented in tables 5 to 8 inclusive. In these tables the treatments are recorded by symbols as indicated in the following list:

Treatments:

A. Seeds rolled In 10 percent DDTr.

B. DDT (10 percent) sprinkled in the furrow when planted at
the rate of 1 ounce to 10 feet of row.

C.* DDT (5 percent) dusted on foliage at the rate off 80 pounds
per acre.

D.* DDTI (5 percent) dusted on foliage at the rate of 140 pounds
per acre.

E. Check, untreated.

*Dusting was done under a canvas cover to prevent any drifting
of the insecticide to other plots off the experiment.

Table 5. Number of plants growing from 120 pea seeds in 1944.


Blocks ITreatment
Treatment 1: ] 2 1_ 3 1 14 51 totals

A 98 107 118 107 110 5140
B 106 104 97 111 112 530
C 110 94 108 115 112 539
D 115 111 100 109 107 542
E 112 107 112 105 106 542





-9

The germination of the peas in the different treatments of the DI experiment is recorded in table 5. The number of seeds planted was 120 in each plot. The treatment had no effect on the germinationI

Table 6. Numbers of pea seed harvested from plots receiving different treatments with DI in 1944.
...... I_ m Blocks .. !- .. Treatment
Treatments "i -....2 1 "3 4 _i ....5 i6-1 totals

A 713 827 994 951 1025 1036 5546
B 990 607 883 865 1303 888 5536
C 753 972 1240 723 1492 1070 6250
D 1210 1207 1065 900 1030 945 6357
E 887 792 973 825 1340 1087 5904


The number of pe& seeds harvested from the treatment plots of
the experiment with DDT,, as shown in table 6, did not vary much with the treatments. The two treatments (A and B) where DOT was placed below the surface of the soil had slightly fewer peas, and the ones with DDT on the foliage (C and D) had slightly more than the untreated check plots. The difference is small and can be attributed to chance.

Table 7. Weight of pea seed harvested from plots redeiving
different treatments with DIV in 1944,


Tratenj 2 Blocks featment
Treatment 1 7 L3 1 5 Totals
GX= G Grams Grams Gas Gg rm
A 169 118 210 202 216 215 1200
B 211 133 185 180 267 192 1168
C 169 218 264 156 312 230 1349
D 254 259 233 195 225 194 1360
B 195 168 215 175 285 224 1262




UNIVERSITY OF FLORIDA


-~ 1262 09238 7421
The weights of pea seed harvested from the plots in the experiment on DT1 are given in table 7~. The differences are small and may be chance variations. Those plots where the DDTI was placed below the soil surface have a slightly lower yield than the checks, but the difference Was not 8igaificant.

Tr-le 8. ofgb cr ea straw harvested from plots receiving
different treatments with DDXT in 1944.


B locks jTreatment
Treatmentl1 12 1 3 j 1 5 6 Totals
Grams Grams Grams Grams Grams Grams Grams
A 237 253 284 236 296 263 1570
B 263 229 225 253 315 255 15140
C 281 264 303 266 330 296 1740
D 297 288 336 287 283 275 1766
E 236 265 306 261 313 256 1637


There is comparatively little difference between the yields of straw as recorded in table 8. Here, too, the yield was smaller on plots where DDT] was placed below the soil surface and larger where it was dusgted an the foliage.

There was no difference in the pea plants that can be associated with the DDT treatments. The variation between blocks indicated differences of location which account for the differences between
treatment yields.

Conc lus ions

Contrary to previously published information, these experiments indicate that Dr~r promises to be an effective insecticide for pea weevil control. Applied to the vines and in the soil in the seed furrow, it was not toxic to the pea plant. In laboratory tests, DDT' showed a tendency to have greater toxicity to the pea weevil at 700 F. than at 860 F., a feature that ill add to the effectiveness of this insecticide if the finding is substantia~l-ed in future field tests.

Two important features remain to be determined concerning this insecticide. These are the duration of its effective period on the pea vines, and whether the material has any repellent effect on the pea weevil.