Tests of insecticides for grasshopper control, 1947

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Title:
Tests of insecticides for grasshopper control, 1947
Physical Description:
18 p. : ; 27 cm.
Language:
English
Creator:
Parker, J. R
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

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Subjects / Keywords:
Insecticides -- Testing   ( lcsh )
Grasshoppers -- Control   ( lcsh )
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federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 13).
Statement of Responsibility:
compiled by J.R. Parker.
General Note:
Caption title.
General Note:
"E-774."
General Note:
"March 1949."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030293696
oclc - 780157915
System ID:
AA00025166:00001

Full Text
LIBP 'ARY
STATE PLANT BOARD
March 1949 E-774

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



TESTS OF INSECTICIDES FOR
GRASSHOPPER CONTROL, 1947 /

Compiled by J. R. Parker
Division of Cereal and Forage Insect Investigations


Of the new insecticides tested against grasshoppers in alfalfa in
Montana, Arizona, and California in 1946, chlordane, toxaphene
(chlorinated camphene), and benzene hexachloride gave the most
promising results (Hinman and Cowan 1). Additional tests with these
and several other new insecticides were made in 1947, and are reported
herein. The materials were tested in the laboratory during the winter
to select effective dosages which could be used as starting points in
field tests during the normal grasshopper season. These results are
not to be construed as recommendations for any of the insecticides tested.
All of them are more or less toxic to warm-blooded animals. They would
therefore have to be used with suitable precautions, which will not be
discussed in this paper.

SPRAYS AND DUSTS

Methods and Conditions

Laboratory Tests.--Insecticides were tested in the laboratory during
the winter to select minimum effective dosages that could be used in
initial field tests during the grasshopper season. All spraying and dusting
were done in an open-top sheet-metal drum 28.3 inches in diameter
(1/10,000 acre) by 13 inches deep. A false bottom 4 inches from the base
of the drum left a treatment chamber 9 inches deep. The inside was lined
with wrapping paper, which was replaced after each application of insecti-
cide. This drum was mounted on a turntable and revolved at 90 revolutions
per minute.

I/ These tests were conducted by F. T. Cowan, E. J. Hinman, J. R.
Parker, Lee Seaton, and F. E. Skogg, of Bozeman, Mont.; 0. L. Barnes
and N. J. Nerney, of Tempe, Ariz; and C. C. Wilson, of Sacramento,
Calif. In Arizona and Montana the Division of Grasshopper Control
purchased the insecticides and provided equipment for their application.
In California the Shell Agricultural Laboratory and the State Department
of Agriculture supplied materials and equipment and assisted in field work.


AP I ?-






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All sprays were atomized into the chamber from a DeVilbiss hand-
atomizer nozzle mounted over the spray chamber. The spray was
directed downward toward a point midway between the center and the
edge of the drum. Dosages corresponding to various rates per acre
were measured to an accuracy within 0.05 ml. At the lowest dosage
tested, corresponding to 2 gallons per acre, this measurement was
accurate to within 13 percent.
All dusts were applied with an improvised duster designed to handle
the small amounts of materials used in these tests. Weighed amounts
of dust corresponding to the desired rate per acre were used, and
although the accuracy was probably not so high as in the spray tests,
it was believed to be adequate.
Compressed air for both dusting and spraying was supplied by a
small motor-driven diaphragm pump connected to the atomizer nozzle
or duster through a pressure regulator. A pressure gage was located on
the low-pressure side of the regulator. With this apparatus a constant
air pressure up to 20 pounds per square inch could be maintained.
Soybean plants 3 to 6 inches high in 4-inch flowerpots were used as
the test plants. Holes in the false bottom of the drum accommodated
the flowerpots so that the tops were nearly level with the bottom of the
treatment chamber.
The grasshoppers used were mostly late instars or adults of
Melanoplus differentialis which had been reared in the laboratory. In
most of the tests the grasshoppers and soybean plants were treated
simultaneously, but in some tests they were sprayed separately. The
grasshoppers were placed in the chamber along with the soybean plants
just before the spray or dust was applied and removed as quickly as
possible after treatment. They were then placed with treated or untreated
plants in screen cages for observation of mortality and other reactions.
Fifteen grasshoppers were placed in each cage, and duplicate cages
were used in each test.
Field Tests.--Spraying and dusting tests were begun by members of the
Bozeman staff in the Salt River Valley, Arizona, on April 10, and continued
to May 5. Most of these tests were conducted in medium to heavy stands
of irrigated alfalfa. Members of the Tempe staff conducted tests in the
same locality throughout the 1947 season. Their work included treat-
ment of citrus trees as well as alfalfa. In California most of the tests
were conducted in Ladino clover or trap strips of alfalfa during May,
June, and July. In Montana all tests were carried out in fields of green
alfalfa during July, August, and September.
Melanoplus mexicanus (Sauss.) was the most abundant species
encountered during the early season in Arizona. Melanoplus differenti-
alis (Thos.) and second-generation M. mexicanus were dominant later
in the year. Melanoplus differentials and M. femur-rubrum (Deg.)






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were the most common species in Montana. The work in California was
done with infestations of M. marginatus (Scudd.), Camnula pellucida
Scudd., M. differentialis, and M. femur-rubrum.
In the early-season tests in Arizona spray applications from the
ground were made with a turbine-blower sprayer-duster. This machine
delivered 8 gallons of emulsion spray per acre in 2-rod strips at a
ground speed of 5 miles per hour. When concentrated sprays were used,
the machine was fitted with a special spray bar that reduced the rate of
application to 2.5 gallons per acre.
Ground applications by members of the Tempe staff were made with
a turbine-blower sprayer-duster, high-pressure power sprayers, or a
6-nozzle power duster. At the Sacramento station emulsions and sus-
pensions were applied with a high-pressure power sprayer equipped
with a boom, and oil solutions with a sprayer especially designed for
discharging finely divided concentrated solutions.
Applications of insecticides by airplane were made with a Bureau-
owned White Standard biplane equipped with a spinner-disk spray device,
and with commercial dusting and spraying planes. Emulsions and oil
solutions were in most cases prepared from a concentrated solution of
the insecticide in petroleum distillate No. 1 fuel oil. Y/ Stocks were
prepared so that an easily measured quantity, such as 1 quart, contained
1 pound of insecticide. Solutions were prepared by further dilution of
the concentrate with the solvent. For the emulsions an oil-soluble
emulsifier (Igepal No. 300) V was added at the rate of 100 ml. (approx-
imately 3.4 fluid ounces) per gallon, and the resulting concentrate
diluted with water to the desired strength. Water suspensions were
made from wettable powders as obtained from manufacturers. All dusts
were factory-mixed or diluted from factory-mixed dusts by commercial
insecticide companies.
The insecticides were first tested on small plots ( to 2 acres) to
determine the most desirable form and rate of application and for
comparison with each other. When suitable procedures had been devel-
oped, treatments were applied to larger plots under more varied con-
ditions.
The results of all the tests conducted in Arizona were evaluated by
sweeping with an insect net on treated and adjacent untreated plots before
and after treatment. The ratio of grasshoppers per sweep on the plots
assigned for treatment to those on the check plot would be expected to
remain constant except for the effect of the treatment. The percentage

3/ Flash points, 100 F. minimum, 165F. maximum; boiling range
440-560 F.; maximum sulfur 0.5 percent.

Y/ A condensation product of ethylene oxide and an alkylated cresol.






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reduction, or kill, was determined by an adaption of Abbott's formula--
dividing the reduction in this ratio by the ratio obtained before treat-
ment and multiplying by 100.
The results of the tests in California were evaluated by means of
counts of live hoppers per unit area (1 square foot or 1 square yard)
before treatment and of dead and live hoppers per unit area after treat-
ment.
Unless stated otherwise in the text, the kills reported are based on
final sweepings or counts made 3 to 4 days after treatment.

Chlordane

In 1946 chlordane gave excellent results when used as an oil emul-
sion but was not tested in oil solutions. In 1947 oil solutions of chlordane
were tested first in the laboratory and then in the field to determine
whether they were as effective as emulsions. Oil solutions have the
advantage of requiring no water. This saves labor, speeds up spraying
operations, and eliminates the possibility of using highly alkaline water,
which might react unfavorably with the insecticide used.
Laboratory Tests.--At the Bozeman station adult grasshoppers
(Melanoplus differentialis) and soybean plants were sprayed simultane-
ously with chlordane at the rate of 1 pound in 2 gallons of petroleum
solvent per acre. Treated grasshoppers and plants were held in screen
cages for 24 hours. The average mortality for 10 replicates was 93
percent.
The results were considered sufficiently good to warrant using
chlordane-oil solutions at this dosage in initial field tests.
Field Tests.--The field tests with chlordane were conducted in
Arizona, Montana, and California. The details of the tests and the
results obtained are summarized in table 1.
Chlordane was equally effective in oil solutions and emulsions and
in ground and airplane applications. A dosage of 1 pound per acre
reduced grasshopper populations 90 to 99 percent in 3 days or less
under a wide variety of conditions. A suspension at this dosage gave
90 percent kill in limited tests in Arizona. When compared directly
in airplane applications in Arizona, dusts gave 71 percent, solutions
96 percent, and emulsions 98 percent kill.
The field tests therefore confirmed the laboratory tests, which
showed that 1 pound of chlordane per acre in solution or emulsion was
sufficient to give 90 percent or greater reduction in 3 days, and suspen-
sions appeared to be almost as effective. Dusts were in general less
effective, and when applied to dry vegetation late in the summer failed
to give economic control.







-5-


Chlordane affects grasshoppers within a few hours. Speed of kill
and duration of toxicity depend largely upon the dosage. With 1 pound
per acre in oil solutions and emulsions the population present during
treatment is frequently reduced 90 percent in 1 day and close to 100
.percent in 3 days. Under such conditions the killing action after 3 days
cannot be measured unless a new population hatches within the field or
moves into it from the outside. When only small numbers of late-instar
nymphs and adults are found, it is impossible to determine whether they
have fed on treated foliage and survived or have only recently moved
into the field. The only exact method of determining how long the in-
secticide remains effective is to search the treated plots daily for
freshly killed grasshoppers. This procedure is time-consuming and
frequently impossible because of irrigating, harvesting, or grazing
practices.
General observations on the residual action of chlordane were made
in Arizona and California. In Arizona the 1-pounid dosage continued to kill
grasshoppers for 15 to 30 days, but in one test there was no residual
effect on grasshoppers that hatched in the plots more than 7 days after
treatment. In California an oil solution remained toxic 15 to 17 days.
No injury to foliage was observed following the application of chlor-
dane dusts or suspensions. Some spotting and wilting of alfalfa foliage
was noted where oil solutions were inadvertently applied in dosages
heavier than needed. This injury was undoubtedly caused by the solvent.
When dosages were evenly distributed over entire plots, foliage injury
was insignificant.

Toxaphene

Tests of toxaphene in 1946 were limited to a few late in the season
at dosages of 2 to 8 pounds per acre. The excellent kills obtained
indicated that it should be tested extensively in 1947.
Laboratory Tests.--Toxaphene at dosages of 0.5 to 4 pounds per
acre in 8 gallons of emulsion was used in 10 tests, in which adult grass-
hoppers and soybean plants were sprayed together. The 0.5-pound
dosage killed 26 percent of the grasshoppers in 24 hours and 92 per-
cent in 48 hours. Dosages of 1 to 4 pounds killed from 58 to 95 percent
in 24 hours and 87 to 100 percent in 48 hours. From these tests it was
concluded that 1 pound per acre applied as an oil emulsion was close
to the minimum effective dosage under laboratory conditions.
One pound of toxaphene in 2 gallons of solution per acre was used in
30 tests to compare the effects of spraying grasshoppers and plants
separately and together. When sprayed grasshoppers were placed on
untreated plants, the mortality averaged 84 percent in 24 hours and
96 percent in 48 hours. When untreated grasshoppers were placed on






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sprayed plants, the mortality averaged 64 percent in 24 hours and 93
percent in 48 hours. When the grasshoppers and plants were both
sprayed, the mortality averaged 98 percent in 24 hours. The high
mortality obtained by placing sprayed grasshoppers on untreated
plants indicates that toxaphene is very effective as a contact
poison.
The residual action of toxaphene was investigated by spraying soy-
bean plants with an emulsion at a dosage of 2 pounds in 8 gallons and
holding the plants for 7 days before allowing untreated grasshoppers
to feed on them. In 5 tests the average mortalities 24, 48, and 72 hours
after feeding were 24, 58, and 89 percent. When untreated grasshoppers.
were placed upon freshly sprayed soybean plants treated at the same
rate per acre, the average mortality was 78 percent in 24 hours and 98
percent in 48 hours.
Toxaphene applied at 2 pounds per acre in a 10-percent dust was
used in 10 tests in which grasshoppers and plants were dusted together.
Mortalities averaged 59 percent in 24 hours and 95 percent in 48 hours,
and were slightly less than the kills obtained with 1-pound dosages
applied in oil solution or emulsion.
The results of the laboratory tests were considered sufficiently goodto
warrant using toxaphene in preliminary field tests at acre dosages of 1
pound in solution and emulsion sprays and of 2 pounds in dusts.
Field Tests.--Field tests with toxaphene were made in Arizona,
Montana, and California. The details of the tests are summarized in
table 2.
Toxaphene was almost equally effective in oil solutions and emulsions
and in ground and airplane applications. At a dosage of 1 pound per acre
the average kill in 3 days with both formulations was 90 percent, and at
1.5 pounds per acre in an emulsion 90 percent kill was obtained in 1 day
and 98 percent in 5 days. Suspensions gave 78 percent kill in 3 days at
1 pound per acre, and 89 and 96 percent at 2 pounds. Dusts were tested
at various strengths and dosages, but the highest kill was 89 percent
per acre with a 10-percent dust applied at the rate of 2 pounds of
toxaphene.
Toxaphene was slightly less effective in field tests than in the
laboratory. In solution and emulsion the 1.5-pound dosage gave
quicker kill and longer toxic effect than the 1-pound dosage, and is
therefore recommended for best results. To obtain the same kill with
suspensions and dusts 2 pounds per acre was necessary.
Toxaphene affects grasshoppers within a few hours after treatment.
Speed of kill and duration of residual action are nearly the same as re-
ported for chlordane.
No injury to foliage was noted when dosages were evenly distributed.
Excess application of oil solutions occasionally caused some spotting of
alfalfa foliage.






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Benzene Hexachloride

Field tests were made with benzene hexachloride in Arizona and
Montana. Because of the danger of foliage injury due to the solvent
where solutions and emulsions are used, emphasis was placed on
testing water suspensions and dusts. Oil solutions were tested only on
small acreages in California.
The results of these tests are summarized in table 3. All dosages
are in terms of the gamma isomer, although the technical benzene
hexachloride containing all four isomers was used.
Benzene hexachloride, as in 1946, was erratic in performance. In
Arizona, in tests on the same day, the kill after 1 day with 0.15 pound
of gamma isomer per acre in water suspension was 79 percent whereas
with 0.25 pound it was only 61 percent. In 7 tests kills with 0.4 pound
in dust ranged from 49 to 99 percent, averaging 87 percent. In Montana
average kills after 1 day with 0.3 pound in dust and 0.36 pound in water
suspension were 65 and 73 percent. In California kills with only 0.114
pound in water suspensions and 0.15 pound in oil solutions averaged
better than 90 percent. In view of the variable results, no statement
can be made in regard to minimum dosages needed for consistently
high kills.
Benzene hexachloride affects grasshoppers within a few hours after
treatment and most of the kill occurs within 1 day. There is little or no
residual toxicity after 4 to 5 days.
No foliage injury was noted with any of the formulations and dosages
used in 1947.

Hexaethyl Tetraphosphate

Hexaethyl tetraphosphate (active ingredient tetraethyl pyrophosphate)
was used in 32 laboratory and 22 field tests. It is a liquid which hydro-
lyzes rapidly with water. Its chemical character, stability, and insecti-
cidal efficiency may vary with the method used in making it. The
material tested in the laboratory at Bozeman and in the field in Arizona
was labeled "Hexaethyl tetraphosphate, 100 percent." Preparations
containing 25 and 50 percent of hexaethyl tetraphosphate were used in
California.
Laboratory Tests.--Hexaethyl tetraphosphate was used in a prelim-
inary series of 10 tests at acre-dosages of 0.5 to 4 pounds in 8 gallons
of water. Grasshoppers and food plants were sprayed together. Average
kills in 1 day for 2 tests at each dosage were as follows: 0.5 pound, 56
percent; 1 pound, 88 percent; 2, 3, and 4 pounds, 100 percent. In a second
series of 10 tests with 1 pound per acre the average kill was 99 percent.
In 6 tests in which grasshoppers were sprayed at the 1-pound rate and






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placed on untreated foliage, the average kill was 89 percent. In 6 tests
in xhich untreated grasshoppers were placed on foliage treated at the
1-pound rate, the average kill was only 35 percent. The results of the
laboratory tests were considered sufficient to warrant using 1 pound of
hexaethyl tetraphosphate in 8 gallons of water per acre in preliminary
field tests. They also indicated that it was primarily a contact poison.
Field Tests.--Field tests were conducted in Arizona and California.
The results of these tests, which are summarized in table 4, failed to
support the indications of the laboratory tests. Kills with 1 pound per
acre averaged only 35 percent. Most of the grasshoppers were affected
within a few minutes after spraying. Many twitched spasmodically and
others were unable to jump or walk. Those that recovered behaved
normally within a few hours. There was no increase in kill after 1 day.
Field tests in California demonstrated that an acre-dosage of 1.35
pounds in 50 gallons of water or 5 gallons of oil was sufficient to obtain
kills of 90 percent or better in 1 day. In these tests many grasshoppers
were killed in less than 30 minutes. There was no increase in kill after
1 day.
No injury to foiag.le was noted with the formulations and dosages
u d.

Parathion

The results of field tests with parathion in Arizona and California
are summarized in table 5.
Parathion at 0.4 pound per acre as a dust gave consistent kills of 90
percent or better in 3 days. In water-suspension sprays at 0.75 to 1 5
pounds the Milv was 100 percent.
Parathion killed very quickly. Dead and dying grasshoppers were
noted within 1 hour, and high mortalities were recorded after 4 hours.
Killing action continued for at least 5 days.
No injury to foliage was noted with the formulations and the dosages
us --...


BAITS

New insecticides that had shown promise in grasshopper control
when used as sprays and dusts were tested in grasshopper baits in
Arizona and Montana during the 1947 field season. Since nearly all
tests were comparisons of two or more insecticides, the results are
reported under general headings instead of in separate sections on each
insecticide.






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Methods and Conditions

All tests were conducted in the field. In Arizona tests '. ma
only on plots; in Montana tests were made on plots and in outdoor c
,-_,,es. Uniform procedures were followed in conducting plot tests
A rlications were made on 1.25- to 5-acre alfalfa plots at the rte o
pounds of dry carrier per acre with a bait broadcaster. When available
green alfalfa 6 to 27 inches tall was selected. Generally six or more
tests were made with each bait in each series. Unless otherwise s c
ified, the carrier was a mixture of 3 parts of bran and 1 part of sawdus'
by volume, and enough water, usually about 12 .lions, was added to each
100 pounds of carrier to make a moist, crumbly mash. In this report
the quantity of a toxicant mentioned is the amount used per 100 poundss
of carrier. Counts were made of the grasshoppers taken in s'., pings
of treated and untreated check areas before and after treatment (u .1:.
3 days). Control results were evaluated by the same method used in
tests of sprays and dusts.
For cage tests grasshoppers were collected in the field and trans-
ferred to screen cages, where they were held overnight wil-,'.r- feod.
Approximately 50 grasshoppers were placed in each cage. In the mo:.i.,.;,
when temperatures were favorable for feeding, baits were introduced
The bait was scattered evenly over heavy paper cards, which were then
laid on the bottoms of the cages. At the end of 3 hours the cards and anyi
remaining bait were removed. The cages were stored out of doors but
protected from direct sunlight for 3 days. During this time they v, e-re
kept supplied with fresh, green food, and dead grasshoppers were re-
moved and counted daily. Final counts of dead grasshop -rs and thosi
still alive were made on the third day.
New insecticides used in these tests were benzene hexachloride,
chlordane, toxaphene, and parathion. Sodium fluosilicate, the stand.-
toxicant in grasshopper baits, was included in most tests as a basis of
comparison.

Tests in Arizona

Comparison of Different Poisons.--Wet baits cont;,ininn t, ,': fol ,winr
quantities of the insecticides in 100 pounds of carrier %ere first cor -."ed
in 19 field tests: Sodium fluosilicate 6 pounds, chlordane 0.5 and 1 pound,
toxaphene 1 and 2 pounds, and enough benzene he..xchloride to make 0 3
pound of the gamma isomer. The five baits containing the rew insecti-
cides were about equally effective, grasshopper-population reductions
ranging from 65 to 71 percent. Baits containing the smaller quantities
of chlordane and toxaphene were almost as effective as those cont,
the larger quantities. The reduction with sodium fluosilicate bait was
53 percent, 12 to 18 percent below the reductions obtained with the new






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insecticides. In this series the new insecticides were used in the form
of wettable powders.
In initial tests bait containing 1 pound of toxaphene was as effective
as any bait. Further tests demonstrated the superiority of 1 pound of
this material over 6 pounds of sodium fluosilicate. In comparison on
5-acre plots of green alfalfa in mid-July the kill with toxaphene was 77
percent 1 day after treatment and 82 percent in 3 days. With sodium
fluosilicate the respective kills were 67 and 72 percent. In 62 direct
comparisons during the 1947 season, the average kills in 3 days were
47 percent with 6 pounds of sodium fluosilicate and 60 percent with 1
pound of toxaphene.
Sodium fluosilicate, parathion, and benzene hexachloride were
compared in wet baits in six additional field tests. Benzene hexachloride
and parathion were supplied in the wettable-powder form and sodium
fluosilicate as the undiluted powder. The average grasshopper reductions
were as follows: Sodium fluosilicate 6 pounds, 66 percent; parathion
1 pound, 70 percent; and benzene hexachloride 0.2 pound gamma, 73
percent.
Comparison of Different Quantities of Insecticides in Baits.--The
ifectiveness of baits containing 0.1, 0.2, and 0.3 pound of the gamma
isomer of benzene hexachloride was compared in 12 field tests.
Average grasshopper-population reductions were 78, 79, and 84 per-
cent, respectively. These tests indicated that 0.1 pound was about as
effective as 0.2 and 0.3 pound. In five other tests with baits containing
0.025, 0.05, and 0.1 pound of the gamma isomer, grasshopper reductions
averaged 25, 32, and 57 percent. Reducing the gamma-isomer content
-f baits below 0.1 pound per 100 pounds of carrier materially reduced
their effectiveness. The source of the benzene hexachloride used in this
series was a wettable powder containing 5 or 6 percent of the gamma
isomer.
In early tests 1 and 2 pounds of toxaphene per 100 pounds of carrier
were about equally effective in grasshopper baits. In six later tests the
..,ounts were cut to 0.25, 0.5, and 1 pound, and average grasshopper
reductions were 39, 46, and 55 percent, respectively. Pending com-
pletion of more extensive tests, it is believed undesirable to reduce the
concentration below 1 pound per 100 pounds of carrier. The toxaphene
used in this series was in wettable-powder form.
One-half pound of chlordane was about as effective as 1 pound in
tests early in the season. Consequently, in later tests the amounts were
- -:duced to 0.125, 0.25, and 0.5 pound. Average grasshopper reductions
were 79, 85, and 90 percent. Differences in mortality from the baits
containing the different strengths of chlordane were small, but the trend
was toward higher kills with the higher amounts up to 0.5 pound. The
chlordane used in this series was a wettable powder.






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Two field tests were made with different quantities of parathion per
100 pounds of carrier--0.125, 0.25, 0.5, and 1 pound. The average re-
ductions in grasshopper populations were 71, 77, 81, and 92 percent,
respectively. The parathion in this series was a '-ettable powder.
Effectiveness of Baits Containing Different Formulations of Benzene
Hexachloride.--In three field tests wet baits containing 0.2 pound of the
gamma isomer made from a 50-percent benzene hexachloride wettable powder
and from undiluted technical benzene hexachloride (gamma isomer 10
percent) were compared. The technical benzene hexachloride was dis-
solved in xylene and emulsified in water before it was mixed with the
other bait ingredients. The average reduction in grasshopper population
was 84 percent from the bait prepared with the wettable powder and 70
percent from that prepared with the technical benzene hexachloride.
In six other field tests the source formulations were two wettable
powders, one containing 6 percent and the other 10 percent of the gamma
isomer, and an emulsion concentrate containing 9 percent of the gamma
isomer. Again all baits contained 0.2 pound of the gamma isomer and
all were spread wet. The average reductions in grasshopper populations
from these baits were as follows: From 6-percent wettable powder 73
percent, from 10-percent wettable powder 53 percent, and from 9-percent
emulsion concentrate 69 percent.
In these tests best results were obtained with wettable powders con-
taining 5 or 6 percent of the gamma isomer.
Comparison of Wet and Dry Baits.--Two wet and two dry baits were
compared in eight field tests. Each type of bait was tested with two
poisons, 4 pounds of ammonium fluosilicate and 1 pound of toxaphene per
100 pounds of bait. Undiluted technical ammonium fluosilicate powder
was used. Technical toxaphene was dissolved in xylene and emulsified
in water before being mixed with the other bait ingredients. The carrier
was 100-percent bran. In wet baits the water content was 12 to 14 gallons
per 100 pounds of carrier, in dry baits approximately 3 gallons. There
was little difference in effectiveness between the wet and dry baits, as
shown by the following percentage reductions:

Average
Ammonium fluosilicate Toxaphene both poisons


Wet bait
Dry bait


Comparison of Carriers Containing Different Proportions of Bran And
Sawdust.- -Carrier mixtures containing 1 part of bran to 1 part of sawdust
and 3 parts of bran to 1 part of sawdust (all by volume) were tested in 16
field tests. Each mixture was tested with two poisons, sodium fluosilicate
and toxaphene. All baits were wet. Average percentage reductions in
grasshopper populations were as follows:






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Average
Sodium fluosilicate Toxaphene both poisons

1:1 Mixture 42 55 49
3:1 Mixture 46 54 50

There was little difference in the effectiveness of baits containing
different proportions of bran and sawdust.

Tests in Montana

Sodium fluosilicate was compared with -izene hexachloride,
chlordane, and toxaphene in eight tests on plots of green alfalfa during
August. The average kills in 3 days with different poisons were as
follows:
Pounds per 100 Percent
pounds of bait mortality
Sodium fluosilicate 6 32
,enzene hexachloride
(gamma isomer) 0.05 42
.1 44
.3 38
Chlordane .5 34
Toxaphene 1 36
1 38
1.5 38

The average mortalities in this series were low, but no more so
than usual for sodium fluosilicate bait in alfalfa during late summer
in AMontana. There was little difference between baits, and all the new
insecticides were slightly better than sodium fluosilicate.

SUMMARY

Laboratory and field tests with the new insecticides for grasshopper
control were continued in Montana, Arizona, and California in 1947. In
addition to chlordane, toxaphene, and benzene hexachloride, which in
1946 were found to be the most promising, hexaethyl tetraphosphate
and parathion were included in the 1947 tests. All these materials were
tested as sprays or dusts applied by ground machines and airplanes,
and some of them also in grasshopper baits.
When applied in sprays or dusts, chlordane and toxaphene caused
high mortalities within 24 hours and continued to kill over a period of
1 to 4 -v.'eeks. Each of these materials was as effective in oil solution
as in emulsion and when applied from the ground as from airplanes.
Chlordane at 1 pound per acre in such formulations reduced grasshopper






- 13 -


populations 90 to 99 percent in 3 days or less. A suspension at this
dosage gave 90 percent kill, and dusts averti.2 d 99 recent kill when
applied by airplane and 64 percent round ..'Uipnment. To ,}i,.-,
solutions and emulsions at 1 pound c r acre -_,,ve 90 percent kill in 3
days, and emulsions atl 1.5pounds g_-ve 90 percent in 1 day and 98 per-
cent in 5 days. Suspensions gave 78 percent kill in 3 days at 1 pound
per acre and 89 and 96 percent at 2 pounds. With dusts the hi(., st kill
was 89 percent with a 10-percent dust at 2 pounds of toxapherte per acre.
Benzene hexachloride was so erratic in performance that it .,.1,
impossible to select reliable minimum effective dosages; it killed
quickly but had no residual toxicity after 5 'dl:.ys.
Hexaethyl tetraphosphate at 1 pound per acre -a.ive 99 percent kill in
the laboratory but only 35 percent in the LrLld; at 1.35 pounds per acre
mortalities in the field ranged from 90 to 100 percent. This material
had no killing action after 1 day.
Parathion at 0.4 pound per acre in dusts gave consistent kills of 90
percent or hi ,'her; in %ater suspensions at 0.75 to 1.5 pounds per acre
mortalities in 3 days were 100 percent. The killing action continued for
5 days.
in field tests with baits 0.5 pound of chlordane, 1 pound of toxaphene,
1 poui:.d of parathion, or 0.1 pound of thce gamma isomer of benzene
hlex:ichloride per 100 pounds of carrier gave 10 to 15 percent higher kills
than 6 pounds of sodium fluosilicate.

Literature Cited

(1) Hinman, E. J., and Cowan, F. T.
1947. New insecticides in grasshopper control. U. S. Bur. Ent.
and Plant Quar. E-722, 21 pp. (Processed.)













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