iovmber 1944 E-628
United States Department of Agriculture
Agricultural Aesearch Administration
Bureau of Entomology and plant Quarantine
TESTS OF DDT M1XTU?,S AGAINST CODLING MOTH LARVAE
By L. F. Steiner, S. A. Summerland, and C. H. Arnold, Division of Fruit
Insect Investigations, and J. E. Fahey, Division of Insecticide
Because of the promising results obtained with DDT (2,2-bis
(p-chlorophenyl)-l,l,l-trichloroetlane) as a codling moth (Carpocapsa
mooella (L.)) insecticide when used alone or with certain supple-
ments in preliminary tests at Vincennes, Ind., during 1943,-/more
extensive laboratory tests were undertaken during the winter of 1943-44.
These tests were designed to compare the effect of various materials,
including wetting agents, adhesives, and fungicides, as well as methods
of preparation and application, on the efficiency of the DIT deposits
on apples both before and after exposure to tap-water sprays. It is
believed that the results obtained, although not conclusEive, will be
of interest and use to other investigators.
Whole aome Beauty apples, picked green early in September, washed
in 2 percent hydrochloric acid to remove arsenical deposits, and held
in cold storage until needed, were used for the tests. Shortly before
being sprayed, the apples were run, one by one, through two acetone
baths to remove excess wax and provide a uniform and natural fruit
For most tests 80 apples were treated with each mixture. The de-
posits were allowed to dry overnight at 60-700F., ana then the apples
were divided in equal lots. One lot was used without further treat-
ment; the other lot was exposed five times for 4 seconds each to sprays
of tap water, with a 30-second interval between applications, in order
to estimate the probable effect of dasikdng rains on the residual
efficiency of the treatment. In a few tests in which the effect of
rain was not studied only 40 apples Aare treated.
%/ Steiner, L. F., Arnold, C. H., and Summerland, S. A. Laboratory
and field tests of DDT for control of the codling moth. Jour. Fcon.
iEnt. 37x 156-157. 1944.
Sprays were applied with an orchard-type sprayer, remodeled for
laboratory use. It was operated at a pressure of 300 pounds per square
inch. The discharge was from two nozzles set 16 inches apart in a
vertical plane, and so directed that the spray cones would converge on
the fruit 36 inches from the nozzles. The exposure time was 4 seconds,
during which the apples, mounted on wire pins, were revolved twice. In
certain teats of mixtures having deposit-building characteristics the-
apples were exposed to the spray three times at 30-second intervals.
The combined output of the two nozzles was 1.5 gallons per minute.
Although most of the formulas were used in sprays, a few dust
mixtures were tested. Dust applications were made with an orchard-
type power duster arranged so that the discharge would be 20 feet from
the apples. The entire lot of 40 (or 80) pinned apples wus dusted at
once, being turned after half the material had been applied.
Ten newly hatched codling moth larvae were placed on each apple
after it had been ringed with sticky tree-banding material at the
calyx. One lot of 40 unaprayed apples was included in each experi-
The result of each test is expressed as the percent larvicidal
efficiency and is calculated in accordance with Abbott's formula:
Percent efficiency = 100 x 0 number of worm entrances in sprayed fruit
Number of worm entrances in unsprayed fruit/.
The DDT used for these ests was obtained in three forms. A coarse
grade of undiluted material&'was ground in a pebble mill, either with
water to make a paste or in dry form with bentonite, walnut-shell flour,
diatonaceous earth, sulfur, or lead arsenate. This material was also
used with various solvents. The othe5 two forms consisted of a 50:50
DDT-pyrophyl]je (Pyrax ABB) mixture/ and a 39:61 mixture of micronized
DDT and talcS/
_/ Supplied by the Division of insecticide Investigations.
/ Supplied by the Division of Insects Affecting Man and Animals.
The composition or characteristics of certain of the supplements
used in the experiments follow..4
301 oils A paraffin-base 100 percent petroleum oil, with saybolt
viscosity 57 seconds at 1000F., unsulfonated residue
(A.O.A.C.) 84.3 percent
Crude cottonseed or soybean phosphatides, containing 55-60
percent of acetone-insoluble phosphatides
Dreft: Sodium lauryl sulfate, technical
Emulsive-type summer spray oil (98.7 percent), Saybolt viscosity
57.6 seconds at 100YF., unsulfonated residue (A.O.A.C.)
Fermate: Ferric dimethyl dithiocarbaaate
1N-2503z An oil-soluble alcohol sulfate product
Mississippi bentonite: Blue Itawamba class having a low
Soybean oil, containing approximately 3 percent of acetone-
Triton 1956: A phthalic glycerol alkyl resin
Triton X-100;: Polyethylene glycol phenylisooctyl ether
Wyoming bentonite, pellets
lelkin C and ST: Proprietary water-dispersible mixtures contain-
ing 55 percent of soybean lecithin ana cephalin. C
also contains 45 percent of carbitol, ana ST 25 percent
of soybean oil and 20 percent of carbitol
D/ r c nvenience of the reader the proprietary wetting agents
and other supplements used have been listed by name. Such mention does
not imply a recommendation of any particular material in preference to
many others that 1ightt have served similar purposes.
Preparation of spray Mixtures
The usual method of mixing the spray materials was to make a
slurry with any supplements not combined in dry form with the DDT and
a small quantity of water in an electric mixer, and tAen add the DDT.
This mixture was then added to water in the spray tank and the volume
made up to 5, 8, or 10 gallons, depending upon the number of apples
to be sprayed.
In the absence of wetting agents it was not possible to break up
all the small agglomerates of the DDT-pyrophyilite, DDT-talc, or
similar dry mixtures when they were stirred into water. They appeared
as a suspension of particles ranging for the most part up to 1 mm.
in diameter. When such mixtures were sprayed, however, the agglomerates
were broken up and effectively dispersed in the spray droplets.
The DDT-water paste was prepared by grinding 4 parts of DDT with
6 parts of water in a pebble mill. This paste had the consistency
of a thick batter, which dispersed readily upon further dilution.
Effect of Time of Grinaing on Larvicidal Efficiency of DDT-Water Paste
In two experiments DDT was ground with water for different periods
up to 64 hours. DDT was used at 3 ounces per 100 gallons in one
experiment and at 4 ounces in the other. The average results of these
experiments are summarized in table 1.
Table l.--Larvicidal efficiency of DDT-water pastes ground in a
pebble mill for different lengths of time
M Mean surface t Larvicidal efficiency
Time of I particle s Undisturbed s After 5
grinding s diameter deposits t water sprays
Hours Microns Percent Percent
1 9.2 91.5 71.0
2 7.9 90.9 67.0
4 7.0 91.2 58.4
8 6.0 89.8 62.9
16 5.1 94.2 57.1
32 4.4 95.1 66.6
64 4.3 95.6 62.7
Larvicidal Efficiencies of DDT Spray Treatments
Twelve experiments were conducted to determine the larvicidal
efficiency of DDT when combined in different proportions with various
supplements and applied as sprays. Because of differences in larval
vigor or average ability of the mixture of strains of larvae used to
enter the fruit, and in the condition of the fruit as the work pro-
grossed, each experiment must be considered separately. The spray
formulas and the results obtained with them are given in tables 2-13.
The quantities of materials given in the formulas are on the basis
of 100 gallons, and refer to the amounts present in the diluted spray
mixture. Formulas have been numbered for convenience in identifying
these formulas, particularly those tested more than once.
Table 2.-Comparison of various concentrations of DDT-pyrophyllite
(50:50) and DDT-talc (39:61) mixtures, DDT-witer paste (40:60),
and DDT-soybean oil-bentonite
: DDT Larvicidal efficiency.
Supplement : concentration : Formula : Undisturbed t After 5
: per 100 gallons : : deposits : water sprays
Pounds Percent Percent
Pyrophyllite 0.25 1 96.3 -
.50 2 98.9 83.0
1.00 3 100.0 -
Talc .25 4 94.7 -
.50 5 97.3 70.8
1.00 6 98.9 -
Water (paste) .25 7 99.5 -
.50 8 100.0 83.5
1.00 9 100.0 -
Soybean oil 1 qt.
+ Miss. bentonite
0.5 lb. .25 10 91.5 -
Lead arsenate 3 lb.
(check, no DDT) -- 11 56.9
Table 3.-Effect of various supplements on larvicidal efficiency
of DDT-pyrophyllite mixtures applied in sprays at 0.25 pound
of DDT per 100 gallons
Supplement : Formula t Undisturbed : After 5
t deposits : water sprays
None 1 99.4 76.0
Dreft 0.5 oz. 12 97.4 69.5
Yelkin C 0.5 oz. 13 97.4 57.8
Soap (neutral) 1 oz. 14 96.8 67.5
301 oil 1 pt. + Miss.
bentonite 0.5 lb. 15 98.1 85.1
No. 15 + soybean
phosphatides 2 oz. 16 92.9 85.1
No. 15 + soybean
phosphatides 4 oz. 17 94.2 78.6
Table 4.-Evaluation of soybean
of DDT per 1300 gallons
oil in DDT sprays applied at 0.25 pound
Mixture : Formula : Undisturbed : After 5
: : deposits : water sprays
DDT-water paste 7 94.4 68.8
DDT-water paste + Miss.
bentonite 0.5 lb. 18 99.2 69.6
No. 18 + soybean oil 1 qt. 19 98.4 88.0
DDT in soybean oil 1 qt.
+ Miss. bentonite 0.5 lb. 10 94.4 80.8
DDT-water paste + bordeaux
(1/2:1:100) 20 92.8 72.0
No. 20 + soybean oil 1 qt. 21 88.0 75.2
DDT in soybean oil 1 qt.
+ bordeaux 22 77.6 73.6
Table 5.--Comparis=n of various dry supplements when applied with DDT
in sprays at 0.25 pound of DJDT per 100 gallons
: : Larvicidal efficiency
Supplement/ : Formula : Undisturbed : After 5
: : deposits : water sprays
Water paste (check) 7 95.1 76.0
Pyrophyllite (50:50) 1 96.7 82.0
Talc (39:61) 4 98.4 77.9
Diatoimaceuas earth (1:2) 23 92.6 72.1
Miss. bentonite (1:3) 24 91.8 67.2
Walnut-shell flour (1:3) 25 100.0 75.4
Hydrteid lime (1:3) 26 88.5 70.5
./ aatios iiLUcate DDT:supplement.
Table 6.--Ev&aluation of mixtures containing lead arsenate (3 lb.), with
and without DDT (2 oz. in water paste) or a fungicide
... .... .. As;-A. residue Larvicidal efficiency
Material added to : Formula:Undisturbed:After 5:Undisturbed:afterc 5
lead arsenate : :deposits :water deposits :water
Mir:o r__ S rpraya Peren sprays
Micrograms per sq.cm. Percent Peccent
None 11 10.7 6.6 39.8 35.6
DDT-water 27 11.0 6.3 84.5 48.5
Fermate 1 lb. 28 9.6 7.6 34.3 36.0
Fermnate 1 lb. +
DDT-water 29 13.1 9.3 82.4 41.0
Bordeaux (1/2:1:100) 30 9.5 7.0 31.0 28.5
Bordeaux (1/2:1:100) +
DDT-watsr 31 11.6 10.5 84.1 47.3
DDT-water (check, no
lead arsenate) 32 59.4 36.8
Table 7.-Evaluation of sulfur
sprays at 0.25 pound of DDT
in DDT-water paste mixtures, applied in
per 100 gallons
L : arvicidal efficiency
Supplement : Formula : Undisturbed : After 5
: : deposits : water sprays
None 7 95.1 79.5
gtettable sulfur 1.5 lb. 33 95.1 59.0
Dusting sulfur 1.5 lb. +
Draft 0.25 oz. 34 93.2 36.1
Fermate 0.25 lb. 35 94.6 43.4
Flotation sulfur paste 2.5 lb. 36 79.5 38.6
Liquid lime-sulfur 3 pt. 37 89.3 52.2
Table 8.-Evaluation of DDT-lead arsenate dry mixtures (10:90) applied in
SA3203 residue :Larvicidal efficiency
Spray material :Formula:Undisturbed:After 5:Undisturbed:After 5
: :deposits :water :deposits :water
..... .... __ : :sprays : : sprays
Micrograms per sq.cm. Percent Percent
Lead arsenate 2 lb.
11 oz. (check) 39 8.8 6.6 39.6 23.4
DDT (2.4 oz.)-water
paste (check) 40 -90.5 32.4
dry mixture (1.5 lb.)
ground into paste
with water 41 8.1 6.6 86.0 46.9
dry mixture (1.5 lb.) 42 6.0 5.6 64.9 30.6
No. 42 + bordeaux
(1/2:1:103) 43 7.1 5.7 47.3 21.6
No. 43 + 301 oil 1 qt. 44 6.9 6.2 46.8 33.8
No. 44 + Yelkin ST
2 oz. 45 6.8 6.1 45.5 28.4
Table 9.--Camparison of various dry supplements in formulas containing
DDT (0.25 lb.) and soybean oil (1 pt.) applied in sprays
: Larvicial efficietncy
Supplement : Formula : Unaisturbed : After 5
S: deposits : water sprays
Pyrophyllite 1 82.6 39.3
No. 1 + soybean oil + Wyoming
bentonite 0.25 lb. 46 82.2 47.1
Water paste + soybean oil
+ Wyo. bentonite 0.25 lb. 47 75.8 70.8
Talc mixture + soybean oil
+ Wyo. bentonite 0.25 lb. 48 86.4 58.0
Diatomaceous earth (1:2) +
soybean oil 49 68.0 43.8
Miss. bentnnite (1:3) + soybean
oil 50 68.0 55.3
Walnut-shell flour (1:3) + soy-
bean oil 51 78.5 47.5
Table 10.--Effect of various wetting agents added to the DDT-
pyrophyllite mixture when applied in sprays at 1.0 pound of DOT
per 100 gallons
of spray mixture
DRnes per cm.
DDT 0.5 lb.
DDT 1.0 lb.
Triton B 1956
Table ll.--Effect of various supplements, with ana without oil, adaed
to the DDT-pyrophyllite mixture, when applied in sprays at 1.0
pound of DDT per 100 gallons
: eight of
of spray mix
ture at 25O.
Dynes per cm.
DDT 0.5 lb. --
DDT 1.0 lb. --
lelkin ST 0.5
Soybean flour 2.0
Soybean phosphatides 1.0
301 oil 1 pt. + Miss.
bentonite 0.5 lb. -
No. 72 + soybean phos-
phatides 1 oz. --
1 pt. + Miss.
bentonite 0.5 lb. --
Soybean oil 1 pt. +
Miss. bentoni te
0.5 lb. --
Table 12.--Comparison of several emulsion formulas with DDT-pyrophyllite
mixture when applied in sprays at 0.25 pound of DDT per 100 gallons
: :Larvicidal efficiency
:Formula : Undisturbed : After 5
S: deposits : water
Benzene 9.7 )z. Triton B-1956 1.5 oz. 76 57.6 36.2
Ethylene dichloride Suifonated castor
13.3 3z. oil (50%) 1.3 oz. 77 46.3 36.1
iylane 13.3 oz. Triton X-100 1.3 oz. 78 47.9 28.6
mixture (check) 1 81.5 41.2
Table 13.-Effect of spraying time on efficiency of DDT-pyrophyllite
mixtures when applied in sproys at 0.25 pound of DDT per 100 gallons
: Larvicidal efficiency
: when spraying time was-
Material added to DDT-pyrophylite : Formula :
: 4 seconds : 12 seconds
_ ---- _- : - : ,- i - .......
Miss. bentonite 0.5 lb. and Feralate
0.25 Ib. in slurry + 301 oil 1 qt. 82 97.1 98.9
No. 82 + soybean phosphatides 2 oz.
suspended in oil 83 93.7 100.0
No. 82 + cott-nseed phosphatides ; oz.
suspended in oil 84 93.1 98.3
Larvicidal Efficiencies of DDT Dusts
The few tests made with dust mixtures are presented in table 14.
It will be noted that formula 38 cannot be compared directly with the
other formulas, because the test was conducted at a different time.
Table l4.-Larvicidal efficiency of various DDT-talc mixtures applied
t Quantity : : LArvicidal efficiency
i applied : Formula : Undisturbed : After 5
: to 80 : : deposits : water sprays
: aDDle B :
Ounces Percent Percent
DDT-talo (39:61) 2 38 99.0 63.9
DDT-talc (10:90) 6 79 97.1 40.0
(10:40:50) 6 80 98.3 4.5
(10188:2) 6 81 98.7 46.7
Because of the high toxicity of DDT, in order to bring out differ-
ences it was applied in lower concentrations than woulc be practical
under field conditions. On this account it seemed desirable to reduce
proportionately most of the supplements, where wetting agents were
employed, however, only the maximum quantities tested increased notice-
ably the ease with which the VDT could be dispersed in water to make
a moderately thick slurry. The higher concentrations required for
field uae (approximately 1 lb. of DDT per 100 gal. for the coaling moth)
would therefore require more of the wetting agent to make a slurry
of the same consistency.
One of the most important developments in these tests was the
performance of those mixtures not containing wetting agents, particularly
the water paste and the pyrophyllite and talc preparations. There was
no evidence that the wetting agents would improve the efficiency of
any of the DDT formulas, and in many instances they tended to reduce
the efficiency both before and after exposure to tap-water sprays.
The probable usefulness of DDT in paste form was suggested by
results obtained in laboratory-field tests in 1943 after DDT had been
ground for short periods with water in a thin slurry. The differences
between the paste and the DDT-pyrophyllite mixture, however, were not
mathematically significant (tables 2 and 5). DDT combined with crude
soybean oil and enough Wyoming bentonite to prevent "breaking" in the
tank (formula 47) proved more effective after the tap-water sprays than
mixtures containing pyrophyllite, talc, diatomaceous earth, Mississippi
bentonite, or walnut-shell flour.
Length of grinding had a definite effect on particle size (table 1).
The results indicate that the efficiency of unweathered deposits might
be improved by grinding to a mean surface particle diameter of 4 to
5 microns but that the ability of the deposits to withstand the
artificial rain weathering diminished as the diameter was reduced
below approximately 9 microns. The paste used in most of the experi-
ments was ground approximately 36 hours.
DDT dissolved in soybean oil (formulas 10 and 22), benzene,
ethylene dichloride, or xylene (table 12) was much less effective than
when used alone in a water suspension. After the tap-water sprays
the DDT paste or pyrophyllite mixture gave better results when added
to bentonite-soybean oil or petroleum oil emulsions (tables 3, 4, and 11)
than when used alone. Such mixtures are promising, particularly where
some deposit-building action can be obtained, as with formulas 83 and
84. In these formulas the presence of ferric dimethyl dithiocarbamate
increased the deposit-building action of the DDT-oil-phosphatide mixture.
Other metallic salts woula probably do likewise. Fruit sprayed con-
tinuously for 30 seconds with these mixtures acquired a thick,, even,
Although a weak bordeaux can be used with DDT without seriously
reducing its efficiency (table 4), the various forms of sulfur (table 7)
reduced the efficiency of deposits exposed to the tap-water sprays.
DDT in combination with lead arsenate (tables 6 and 8) was uost
effective when the two were added to the spray mixture separately or
ground with water to form a paste. The dry mixture was too granular.
DDT promises to be a very effective fortifying agent for lead arsenate
at dilutions as low as 2 ounces per 100 gallons. In formaul&s 29 and
31 it appeared to increase the deposits of arsenious oxide.
Among the most promising developments in this series of tests
were the results obtained with the dust mixtures (table 14), particularly
those containing sulfur and oil.
Since the completion of these experiments a technique for the
analysis of.4DT deposits on fruit has been developed at the Vincennes
laboratory.2/ On fruit similar to that employed in the larvicidal
efficiency experiments, but not treated to remove excess wax, deposits
of 5.2, 10.9, 22.0, and 48.8 micrograms oCDDT per square centimeter
were obtained with spray mixtures containing DDT paste equivalent to
05,5 1, 2, and 4 pounds of DDT to 100 gallons. Sprays of DDT-pyrophyl-
lite employing 3 pounds of DDT to 100 gallons, alone and with Missis-
sippi bentonite and soybean oil (formulas similar to Nos. 1 and 75),
gave deposits of 21.7 and 38.0 micrograms of DDT per square centimeter.
/ Fahey, J. E. The determination of DDT spray deposits on apples.
Assoc. Off. Agr. Chem. Jour. Submitted for publication.
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