New insecticides in grasshopper control

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Material Information

Title:
New insecticides in grasshopper control
Physical Description:
21 p. : ; 27 cm.
Language:
English
Creator:
Hinman, E. J
Cowan, F. T
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:

Subjects

Subjects / Keywords:
Insecticides -- Testing   ( lcsh )
Grasshoppers -- Control   ( lcsh )
Alfalfa -- Diseases and pests -- Control   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
compiled by E.J. Hinman and F.T. Cowan.
General Note:
Caption title.
General Note:
"E-722."
General Note:
"May 19457."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030293243
oclc - 780092561
System ID:
AA00025154:00001

Full Text
LIEP.ARY
STATE PLANT BOARD




May 1941 E-722

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



NEW INSECTICIDES IN GRASSHOPPER CONTROL

Compiled by E. J. Hinman and F. T. Cowan, I/
Division of Cereal and Forage Insect Investigations


For many years grasshopper control in alfalfa by the use of
poisoned bait has been unsatisfactory. Complete kills have sel-
dom been obtained, and persistent baiting has been necessary in
order to reduce infestations sufficiently to guarantee the harvest
of at least a partial crop of hay or seed from infested fields.
Light infestations in alfalfa being grown for seed often cause
serious reductions in yield. Before the last war alfalfa-seed
production, especially in Montana and Wyoming, was carried on as
a secondary phase in the production of livestock. The common
practice was for the stockman to cut the first crop in June and
leave the second crop for seed. If the seed did not set within
a reasonable time because of grasshoppers or other insects or ad-
verse weather, the crop was cut for hay or pastured. In any case
it was seldom a total loss, and if a seed crop did set the rancher
was well repaid for his efforts.

During the war years the shortage of both alfalfa hay and
seed became acute. This shortage was immediately reflected in the
price of these two commodities. The average price in the United
States for loose alfalfa hay for the period 1935-1940 was $9.34
per ton. The average for 1941-1944 was $15.08. Baled hay on the
Los Angeles market brought an average price of $15.97 for the
period 1935-1940 and $28.02 per ton for 1941-1944. Alfalfa seed
sold at an average price in the United States of $9.46 a bushel
for the period 1932-1940 and $17.09 a bushel for 1941-1944. Thus
over the war years both the hay and seed approximately doubled in
market value. In addition to the normal increase in price of al-
falfa seed, approximately $4.00 per bushel was paid to the grower
in government subsidies. This made a total of 21.09 a bushel,
or more than twice the average price for the years preceding the
war.



1/F. E. Skoog, Lee Seaton, J. R. Parker, 0. L. Barnes, and
C. C. Wilscn, all of this Bureau, assisted in conducting these
tests.

1 r ,**"





-2-


Stimulated by the increased return to be expected from alfalfa
seed, many of the livestock men that had been 7rowinp, the crop as-a
side line expanded their efforts to produce more seed. In Montana
the acreage devoted to seed production during the war was 50 percent
higher than it was prior to 1941. More attention was directed toward
insect control in general and, in these v.estern States particularly,
toward better grasshopper control. These developments emphasized the
need of increasing the efficiency of the poisoned bait or of finding
a more effective method of control. The demand for more efficient
control methods has continued to grow as the price of alfalfa seed
and hay has increased and as the growers have realized the difficulty
of obtaining complete control by baiting. It has been further stimu-
lated by an increase in grasshopper populations in manyof the alfalfa-
growing areas.

Intensive efforts to meet this demand by improving baits and bait-
ing methods have shown some favorable results and are being continued.
The effectiveness of various new insecticides when applied directly to
alfalfa in the form of dusts and sprays is also being determined.
Favorable results have been obtained with some of these insecticides,
and the purpose of this paper is to sunmr.arize the results of the ex-
tensive tests made of them during 1946b.

Tests of various sprays and dusts were started at the Bozeman,
Yont., laboratory in 1945 and continued in Arizona, South Dakota,
comingg, and Montana in 1946. Further tests were conducted in Arizona
by 0. L. Barnes of the Tempe station and in California by C. C. prisonn
of the Sacramento station. Their results are included in this report.
Most of the chemicals used in these tests were furnished by the Divi-
sion of Grasshopper Control at Denver, Colo. The turbine sprayer-
duster, dusting and spraying airplanes, and airplane hire were also
furnished by that Division.

EQUIPMENT AND METHODS USED AND CONDITIONS OF TESTS

Laboratory Tests

In the laboratory all dusting and spraying were done in an open-
top sheet-metal drum 13 1/2 inches in diameter by 12 inches deep.
This drum was mounted on a turntable and revolved at 90 revolutions
per minute during spraying or dusting operations. The inside was lined
with wrapping paper, vhich was replaced after each application of in-
secticide. All sprays wjere 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. Spray dosages corresponding to the desired rate per acre
were measured to an accuracy within 0.05 cc. At the lowest dosage at-
tempted, corresponding to 2 gallons per acre, this measurement was
accurate to within 13 percent.





-3-


All dusts were applied with an ixnprovi;--i duster designed to
handle the small amounts of materials used in these tests. ;:eighed
amounts of dust corresponding to the desired rate per acre were
used, and although the accuracy was probably not so nigh 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 throu-'h a pressure regulator. A pressure gage was located
on the low-pressure side of the regulator. *ith this apparatus a
constant air pressure up to 20 pounds could be maintained or dupli-
cated in any series of tests.

Soyoean plants 3 to 6 inches nigh in 4-inch flower pots -were used
as the test plants. The grasshoppers used were ;,oustly late instars or
adults of Melanoplus differentialis (Thos.) -.ich .'ad been reared in
the laboratory. In most of the tests both the grasshopers and the
potted soybean plants were treated simultaneously. Ifhe grasshoppers
were placed in the chamber along with the soybean plants just before the
spray or dust was applied and removed as quiciKly as possible after
treatment. On removal from the chamber the grasshoppers were caged
over treated or untreated plants in screened-top lantern chimneys for
observation of mortality and other reactions. Fifteen grasshoppers
were placed in each cage, and each phase oT the treatment was dupli-
cated so that 30 grasshoppers were used in each test.

Field Tests

Early-season field tests with various new insecticides were
started by members of the Bozeman laboratory in the salt River Valley
in Arizona on .April 16, 1946, and carried throu-h to Y1ay 13. Most of
tnese tests were conducted in heavy stands of alfalfa and were de-
signed to determine minimum effective dosages. Further tests were
made in South Dakota on roadside infestations and in U'yoming and
kontana on seed alfalfa. The spraying and dusting tests conducted by
3arnes in Arizona were mostly in alfalfa seed crops. Jilson's work
in California was done, for the most part, in 10-foot strips of al-
falfa left uncut in the fields, although some of his tests were made
in mountain meadows consisting mainly of native grasses.

Melanoplus mexizanus (Sauss.) was the most abundant species en-
countered in the early-season tests in Arizona. At first all the
hoppers were in the early instars, but before the tests were finished
M. mexicanus was in the adult sta:e and some local migration was tak-
ing place. Nymphs of L1. differentialis were dominant in the roadside
tests in South Dakota, and nymphs of L. differentialis and M. femur-
rubrumn (Deg.) in the alfalfa-seed fields in coming and Montana.





- 4 -


Iymphs and adults of ::elanoplus differentials and second-genera-
tion nymphs of M. mexicanus were prevalent in the Ariz7oia tests by
3arnes. The dominant species in California were l'. devastator Scudd.
and Camnila e.Llucida Scudd.

In the early-season tests in Arizona applications of sprays and
dusts from the ground we. e made v.ith a power-driven, turbine-blower
sprayer-duster. This iiachine delivered 8 gallons of spray per acre
in 2-rod strips at a ground speed of 5 miles per hour. The same
machine was used in the South Dakota and .,'y:;i:.g tests. one-acre
plots were used in all the tests empoying ground equipment. A small
rotary hard duster ;'as used to apply dusts to 1/10-acre plots in pre-
liminary tests conducted by the staff of tne Tempe, Ariz., station.
Later the plot size w;as increased to 1/4 or 1/2 acre and the dust was
applied with a multiple-nozzle ncwer duster. ^ll dusLs used in
California were applied with a small rnultiple-nozzle power duster,
and sprays were applied ?-ith a single-nozzle, orchard-type power sprayer.

In the first tests with airplane sprays in Arizona a -lications
were made i,,ith a 3ureau-ov.ned -bite Standard biplane equipped Yith a
spinner-disk spray device, and in the later tests they were made with
a privately owned N-3-. plane equip-ed 4ith ordinary disk-ty.e nozzles
evenly spaced along a 30-foot boom. All airplane dust applications in
Arizona were aie with standard commercial equi.pm.ent.

All emulsion srrays were prepared by dissolving the insecticide in
xylene, except in the later tests with technical chlordane for which No. i
petroleum distillate was used as the solvent. An oil-soluble emul-
sifier (Igepal CA) 2/ was added to this concentrate at th3 rate of 100
ml. (approximately 3.4 fl. oz.) per gallon. The concentrate was then
diluted with water to the desired stren-th for spraying. All suspension
sprays were maae from wettable powders. All dusts were factory-mixed.

The results of all tests conducted by members of the Bozeman
laboratory were evaluated by sweeping with an insect net on the
treated and on an adjacent untreated plot before and after treat-
ment. The ratio of the average number of grasshoppers per sweep
on the treated plot to the number per sweep on the check plot
would be expected to remain constant except for the effect of the
treatment. The percentage kill was determined by dividing the
reduction in this ratio by the ratio obtained before treatment
and multiplying by 100. This method of evaluating results is an
adaptation of Abbott's formula.


2/ A condemnation product of ethylene oxide and an alkylated
cresol.









The results of tne Arizona tests conducted by the Tempe staff
were evaluated by sweeping the treated plots before and after treat-
ment and deternni-i.inz the percentaTe reduction in number of live
hoppers present. From 40 to ljO strokes with an insect net were
made on each plot before treatment and at intervals of 1, 3, 4, and
6 days following treatment.

The results of the California tests were evaluated by means of
counts of live hoppers per unit area (1 sq. ft. or 1 sq. yd.) before
treatment and of dead and live hoppers per unit area after treatment.

,fHL,. -) AN E

Laboratory and field tests were made with technical chlordane,
a chlorinated hydrocarbon having the molecular formula C1oH6C18. The
manufacturer's trade nre for this material is "Velsicol 1068," and
it is commonly referred to as "1068." It is a viscous liquid ihich
is considerably heavier than water (sp. gr. 1.70). It is insoluble
in water but soluble in all proportions in organic solvents such as
xylene, acetone, or light petroleum fractions. Although all the
tests were made vwith technical chlordane, in this paper the material
will be referred to as cnlordane.

Laboratory Tests

In a laboratory test at Bozeman, M1ont., which was repeated five
times, unsprayed grasshoppers were confined with sprayed soybean plants
and sprayed hoppers were confined with unsprayed plants. Lach combina-
tion was prepared in duplicate. One cage of each pair was held at a
constant temperature of 85.5S and 50 percent relative humidity while
the other was held at approximately 740 and 49 percent relative humidi-
ty. The emulsion spray was prepared by dissolving 5 fluid ounces of
chlordane in an equal volume of xylene and adding 0.25 fluid ounce of
Igepal CA. This solution was then diluted with water to make 4 gallons,
and was applied as a spray at UW. rate of 0.5 pound of chlordane per
acre. As shown in table 1, the spray gave better kills when it was
applied to the vegetation than when applied directly to the grass-
hoppers. It also performed better at 85.5 than at 74.

An emulsion of identical formula was allowed to stand in a
closed container at room temperature for 1 week. This emulsion
was t,:sted at the rate of 4 gallons per acre in comparison with
a freshly mi killed V5 percent of the grasshoTp rs, whereas the week-old mix-
ture was only ) percent effective. At the end of 72 hours the
fresh spray had effected 100-percent kill and the mortality from
trie aged material had increased to 94 percent. After 1 week in
a closed container the emulsion lad definitely deteriorated, but
not enou-h to destroy its Kiiling povwer anu probable usefuli.J-ss
for field control.





-6-


Table l.--Effect of chlordane on unsprayed grasshoppers fed on
sprayed soybean plants, and on sprayed grasshoppers fed on un-
sprayed soybean plants, and held at different temperatures.
Dosage 0.5 pound per acre. Bozeman, Mont., 1946

Mortality when spray
: Period of :. .was applied to-
Temperature : exposure : Hpe
Plants : Hoppers


0F Hours Percent Percent
85.5 24 80 21
72 100 64
74.0 24 58 8
72 97 60


In most of the earlier tests the grasshoppers were caged with
potted soybean plants in glass lantern chimneys with screen tops.
Because of the consistently high kills obtained the possibility of
fumigation in such cages was suggested. In a preliminary test to
determine whether or not fumigation took place, unsprayed grass-
hoppers were confined in a screen-topped glass lantern chimney
with a soybean plant that had been sprayed .ith the emulsion at
the rate of 0.5 pound of chlordane per acre, but were separated
from contact with it by a screen partition. Within 48 hours 80
percent of the grasshoppers were dead. In another test to compare
results in lantern chimneys with those in cages made entirely of
wire screen, the emulsion sprayed onto the soybean plants at 0.5
pound of chlordane per acre gave 100 percent kill in the glass
cages and 84 percent in the better ventilated screen cages. At
1 pound of chlordane per acre the kill was 100 percent within 48
hours even in the screen cages. It is thus apparent that the
emulsion or some component of it acted as a fumigant.

Field Tests

Field tests with chlordane were of two general types. Plot
tests were carried out to compare this material with other insecti-
cides and to determine the most desirable form and rate of applica-
tion. *'.hen suitable procedures had been developed, treatments were
applied to larger areas such as entire fields of alfalfa or areas
of egg deposition. In such tests, once it had been determined that
the expected mortalities actually occurred, attention was paid to
other effects including undesirable results of the treatments. Whan
this material was tested as an emulsion, the stock solution used was
composed of e.:ual parts by volume of chlordane and xylene, plus 3.4
fluid ounces of an emulsifying agent (Igepal CA) per gallon of the
mixture. This solution was diluted with water to make 4 to 24 gallons
of a spray as needed in order to apply the desired quantity of active
ingredient per acre with the particular equipment to be used. The
results of the plot tests are summarized in table 2.





- 7-


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In 16 tests in which chlordane was applied at the rate of 1 pound
per acre, the average 24-hour mortality was 85 percent. One applica-
tion at 0.75 pound per acre gave a 67-percent kill. Six tests at 0.5
pound per acre averaged 54-percent Kill. Single tests at 1.5 and 2.25
pounds per acre in California gave mortalities of only 25 and 40 per-
cent, respectively, after 4 to 8 days. One pound per acre was the
dosage chosen for further experimental work.

Two dust applications of chlordane at 1 pound per acre averaged
60-percent kill in 24 hours. Twelve tests of chlordane in emulsion
sprays at 1 pound per acre gave 88 percent average mortality. Two dust
tests at 0.5 pound ner acre averaged 55-percent mortality. Three out
of four emulsion spray tests at 0.5 pound per acre averaged 62 percent.
The results of the other test were obscured by a heavy migration of
grasshoppers. At the same rate of application, emulsion sprays were
evidently more effective than dusts.

Chlordane dusts were applied with a conventional-type power duster,
with a turbine-blower sprayer-duster, and by airplane. The results do
not indicate tnat any one of the three is superior for applying this
insecticide in the dust form.

During the tests in '.y.omring an opportunity was afforded to observe
the effects of an emulsion applied with a high-pressure boom-type field
sprayer. The dosage was 1 pound of chlordane in 60 gallons of spray
per acre. The 24-hour kills were lower than from applications of 1
pound per acre of chlordane in 8 gallons of spray with the turbine-
blower. After several days, however, no difference could be detected
in the grasshopper control from the two methods of application.

Comparable morning and evening applications of chlordane were
equally effective.

Chlordane, especially at 1 pound per acre, killed so many grass-
hoppers within the first few days that very few were left to die later.
Only when the populations on the plots were replenished by migrations
or by further hatching did the continued effect of this insecticide be-
come apparent. One plot in Arizona was treated with an emulsion spray
at 1 pound of chlordane per acre on April 24. Grasshoppers continued
to migrate onto and across the plot from a large, dry, weedy area across
the road. Freshly killed grasshoppers could be found on this plot at
any time until May 20, the date the crop was cut. Single applications
of 0.5 pound of chlordane per acre in emulsion sprays to grassy egg-bed
areas in South Dakota gave 90 percent initial kills of first-, second-,
and third-instar nymphs of Melanoplus differentials, but showed little
continued effect. Applications of 1 pound per acre killed nymphs as
they continued to hatch ;on these egg beds for periods up to 1 week,
when a 0.30-inch rainfall stopped the residual effect.





-9-


No undesirable effects were found in experiments which involved
the treatment of entire fields of seed alfalfa. Honeybees that were
moved onto a treated field after dark on the evening the treatment
was applied showed no indication of poisoning or weakening of the
colonies during the following 2-month period. The middle half of this
field was sprayed at this time when in partial bloom, and the two end
portions were sprayed 1 to 2 weeks later when in about full bloom.
The fact that all treated fields showed prospects of a good seed
yield indicated that there was no destruction of any irnse-ts essential
to the pollination of alfalfa.

BENZENE HEXAGHLORIDE

Tests were made in the laboratory and the field with benzene hexa-
chloride, a light gray or nearly colorless powder with a very persistent
musty odor.

Laboratory Tests

The first tests conducted in the laboratory at Bozeman were designed
to establish optimum dosages and to determine whether benzene hexachloride
acted as a contact or a stomach poison. These tests were conducted in
conjunction with those already described for chlordane. The spray ejul-
sion contained 1/8 pound of benzene hexachloride (gamma isomer 10 percent)
in 1 quart of xylene plus 1/4 fluid ounce of Igepal CA and water to make
1 gallon. This spray was used at the rate of 4 gallons ( lb. of benzene
hexachioride, or 0.05 lb. of the gamma isomer) per acre. The results are
given in table 3 and show that benzene hexachloride was more effective
when applied to the vegetation than when applied directly to the hoppers.
Excellent kills were obtained with the 1/2-pound dosage. Higher kills
were also obtained at the lower temperature.

Table 3.--Effect of benzene hexachloride on unsprayed grasshoppers
fed on sprayed soybean plants, and on sprayed grasshoppers fed on
unsprayed soybean plants, and held at different temperatures. Dos-
age J pound (0.05 pound gumma isomer) per acre. Bozeman, Mont.,1946

0 Mortality when spray
Period of : as applied to---
Temperature : exposure ..-...
:: Plants Hopjjers
OF. Hours Percent Percent

85.5 24 88 53
72 100 61
74.0 24 95 78
72 100 86




- 10 -


A similar spray emulsion was allowed to stand in a closed container
for 1 week at room temperature. It was then tested in comparison with
freshly mixed emulsion at 1/2 pound of benzene hexachloride (0.05 pound
of gamma isomer) per acre. The results based on five replications were
practically identical and indicated that the material did not break down
when stored in a closed container for 1 week after being formulated into
an emulsion.

The possible fumigating action of benzene hexachloride, as well as
of chlordane, was tested by confining grasshoppers in screen-top glass
lantern chimneys and in wire-screen cages over soybean plants that had
been sprayed with the emulsion at the rate of 0.5 pound of benzene hexa-
chloride (0.05 pound of gamma isomer) per acre. All the hoppers in the
screen-top glass cages, but only 64 percent of those in the wire-screen
cages, were killed within 48 hours. In a similar experiment with 1
pound (0.1 pound of gamma isomer) per acre all the hoppers held in wire-
screen cages were killed within 48 hours. Apparently the emulsion or
some component of it acted as a fumigant.

Benzene hexachloride as a 10-percent dust was tested in 5 repli-
cations in the laboratory. At 20 pounds per acre (0.2 pound of gamma
isomer) it gave an average kill of 99 percent in 48 hours.

Field Tests

Although laboratory tests conducted at the Bozeman laboratory
indicated that 1 pound of benzene he.achloride (0.1 pound of gamma
isomer) per acre could be expected to give satisfactory control, pre-
liminary tests in the field at 1 and 1.5 pounds per acre in an emul-
sion and 1 pound in a suspension spray gave only mediocre results and
the dosage was increased to 2 pounds. As shown in table 4, the results
of most of the field tests were variable. The stock solution used in
preparing emulsions contained 1 pound of the benzene hexachloride per
gallon of xylene plus 3.4 fluid ounces of emulsifier (Igepal CA). To
this solution enough water was added to permit the application of the
desired dosage of active ingredient with the particular equipment to
be used.

Throughout the season a total of 21 tests of 2 pounds of benzene
hexachloride per acre were made in emulsion sprays, suspension sprays,
and dusts. Under the different conditions of the tests the rcuctions
in populations ranged from 4 to 100 percent, with a general average of
64 percent. A total of 17 tests at a dosage of 3 pounds per acre (0.3
pound gamna isomer) gave from 32 to 100 percent reduction, with an aver-
are of 71 percent. In Barnes' tests in Arizona the dosage was increased
to 6, 7.5, 8, and 10 pounds of oenzene hexachloride, with a correspond-
ing gamua-isomer dosage of 0.6, 0.75, 0.8,and 1.0 pound per acre. In
two tests a 30-percent dust applied at 20 pounds per acre (0.6 pound of









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gamma isomer) gave an average Kill of 76 percent in 3 days. A 40-percent
dust at 20 pounds per acre (0.8 pound of gamma isomer) gave 83-percent
kill in 3 days in a single test. Three tests of a 50-percent dust at 20
pounds per acre (1 pound of gamma isomer) gave an average kill of 86
percent in 3 days. A dosage of 7.5 pounds of benzene hexachloride per
acre (0.75 pound gamma isomer) in a suspension spray applied by plane
gave 80-percent kill in 1 day and 86-percent kill in 4 days. In 'Nilson's
tests in California, 4 pounds of benzene hexachloride (0.4 pound of
gamma isomer) gave an average kill of 66 percent in two trials, Thus
it would appear that the application of 2 pounds of benzene hexachloride
(0.2 pound of gamma isomer) per acre could be expected to kill between
60 and 65 percent of the hoppers, and that 3 pounds per acre approached
an effective dosage. The larger quantities used gave very good kills
in most instances, but may not be economical or much more effective than
the 3-pound dosage.

Comparisons of the effectiveness of benzene hexachloride in
emulsion sprays, suspension sprays, and dusts of varying percent-
ages may be made from the data in table 4. At 2 pounds per acre
(0.2 pound gamma isomer) 9 tests in emulsion sprays gave an average
kill of 70 percent, 3 tests in suspension sprays gave an average
kill of 56 percent, and 8 tests as a dust gave an average kill of 61
percent. Three tests of 3 pounds (0.3 pound gamma isomer) in an
emulsion gave an average kill of 90 percent, whereas 14 tests of
the same dosage in dusts gave an average kill of 67 percent. Three
tests of 4 pounds in a suspension spray gave an average kill of 50
percent. From these results it would appear that the emulsion
sprays are more effective than either the suspension sprays or the
dusts. However, it is necessary to use almost 1 gallon of xylene
to dissolve 1 pound of the crude benzene hexachloride. At a dosage
of 2 pounds per acre approximately 2 gallons are required. This
amount of xylene approaches the point where the spray containing it
is dangerous to plants. The results show that a 3-pound dosage of
benzene hexachloride in xylene emulsion is quite effective, but that
the danger of xylene injury to plants is too great to warrant its
use. If this insecticide is to be applied as an emulsion, it will
apparently be necessary to find a better solvent or one that is less
injurious to plants.

The data do not permit good comparisons between the several
types of ground equipment used in these tests. The applications
made by ground equipment did, however, give somewhat higher kills
than those made by plane. In 19 tests with ground sprayers the
average kill was 67 percent, and in 25 tests of dust applied by
ground equipment it was 66 percent. In 4 tests of sprays applied
by plane it was 59 percent, and in 5 tests of dust applied by plane
it was 49 percent.

The data provide some evidence that benzene hexachloride is
more effective if applied in the evening or during cool, damp weather.
In the early-season work in Arizona three morning tests at 2 pounds
per acre in an emulsion spray gave an average kill of 65 percent,





- 1/4 -


whereas three ever,ing tests witn tr.- same spray and dosage averaged
77-percent mortality and one test at n-jon gave only a 38-percent kill.
,'ilson in California noted that benzene hexachloride a-- arently gave
better kills on cool days.

Little or no continued kill oevond 48 hours was noted in the
early spraying and dusting tests in Arizona. The heavier d:tsar-es
applied by Barnes apparently continued to be effective for 3 to 4
days and t.ose applied by Wilson continued to Kill for 6 days.

METHOXY ANAL,) Cr' DDT

Laboratory Tests

The technical grade of the metho.-,y analog of DDT, 1-trichloro-
2,2-bis(p-rnethoxyphenyl)ethane, --s tested in the laboratory at
Bozeman,i'ont., in 1946 along with benzene hexachloride and technical
chlordane. The results indicated that 2 pounds of this material per
acre would be effective when applied in an emulsion srray, but when
applied at this rate in 5 replications as a 10-percent dust it gave
an average kill of only 34 percent. Higher kills were obtained when
the material was applied to the plants than v.hen applied to the
grassho7 ers, indicating. that it kills mainly as a stomach poison.
Better results were also obtained when treated plants and hoppers
were held at low temperatures.

In tests to determine its stability in an emulsion, this material
showed no decreased kills after beir" allowed to stand in a closed
container at room temperature for 1 week. It was not tested for fumi-
gating action in the laboratory.

Field Tests

The metnoxy analog of DDT w.s thorou-hly tested under field con-
ditions in Arizona, California, and 'you-i -, and the results are shown
in table 5. preliminary tests of emulsion s-ra-:s in the field proved
that a dosage of 2 pounds per acre was ineffective. Five tests by
3arnes conducted soinewhat later, using 2 pounds per acre in a 10-:ercent
lust ,gave an average mortality of 49 percent. In seven tests with both
sprays and dusts applied at the rate of 3 pounds per acre the average
kill was only 48 percent. Four pounds per acre as an emulsion averaged
8O percent kill in three tests. Four and one-half pounds per acre
killed an average of 56 percent when ap lied both as dusts and as
sjrays. Frcor. these results it would seem that the methoxy analog of
DDT at comparable dosaes is less effective than benzene hexacnloride.

Comparisons can be :".de of the methoxy Analj of ';DT at different
percentages in emulsion and suspension sprays and dusts. At 3 pounds
per acre in emulsion sirrys the averaL-e kill was 52 percent in 6 tests.





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One test of this dof.;e in Arizona, aij:led as a 15-percent dust,
killed 27 percent. A 6lmilar te3t in California re.-lted in a
4-percent kill. Four pounds pn-r acre in an -ulsion cave an average
kill of 80 percent in the 3 ','J, LrL. tE-t. In one similar test in
Arizona the results were obscured by migrations. Four and one-half
pounds per acre in a l5-percent dust E'jve an average kill of 56 percent
in 5 tests in Arizona and California. One su z-)ri on spray was applied
by plane but the results were obscured by zil-r.tions. These results
indicate that the methoxy analog of DilT is more effective when applied
in an emulsion spray than when applied as a dust or as a suspension
spray. At 3 pounds per acre the results were not satisfactory. At
4 pounds in the ,yoming tests it beg rin to show effective results, but
the amount of xylene necessary to dissolve 4 pounds (approximately
21 gallons) burned the alfalfa noticeably.

No difference in results was ar rentt when the methoxy analog
of DDT was applied witn various types of.ground eq.iipment, and in
two of the three tests in which it was applied by plane migrations
obscured the results. In the remaining test in which it was used
at 4.5 pounds per acre in a 15-percent dust, a kill of 69 percent
was recorded. This was somewhat hih'her than the average of four
tests of the same dust concentration and dosage applied with ground
equipment in California.

There was some evidence that the methoxy analog of DDT gave
better kills when applied in the e-'er.ing. Four tests with the 3-
pound dtsage in an emulsion applied in the evening gave an average
of 54 percent, -.hriereas two tests with the same dosage applied in
the morning avera eJ 47-percent dill.

A CHL-,. 3i ATIlD CAMI-F Th

A chlorinated c.iP.phene containing 67-69 percent of chlorine and
de.i.r..Ited experimentally as Hercules 3956, is a gupry,,amber-colored
substance in the crude state. t is readily soluble in relatively
small amounts of xylene and No. 1 petroleum distillate, although it
does not go; into solution rapidly.

A small quantity of this material was received at the Bozeman
laboratory early in the sj.ring of 1946. Unfortunately it arrived too
late to be 4iven routine tests in the laboratory and was not in suf-
ficient quantity for field testing. A lar-er supply was received
later and was tested in a small way in the field late in the season
at Hardin, I'ont. ',.all quantities were also received at the 'srmpe,
Ariz., and Sacramento, Calif., laboratories and tested in the field
insofar as Laterials and time woulJ allow. T'he results are shown in
table 6.

Only four tests were completed in Montana, all at the rate of
4 pounds per acre. ,',., of these were with an emulsion s-ray and the


- 16 -









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other two were with a 20-percent dust. The average kill for the two
spray tests was 97 percent and for the two plots receiving the dust,./
95 percent. In Arizona the average kill in two tests with 20 pounds
per acre of a dust containing 10 percent of eehnieal-elhllo ) was
69 percent in 1 day and 88 percent in 3 days. In the California
tests dosages of 2 to 8 pounds per acre gave 100 percent kill in 6
days. Although further work will be necessary to determine the
optimum dosage, it appears that 2 to 3 pounds per acre may be sufficient
to give satisfactory control of grasshoppers.

DUSTS CLTAINIth "FIi- i.LitcIL CYCLOH:.-JLONE" AND PY-ETHRUL!

Twelve dusts containing Piperonyl Cyclohexenone and pyrethrum
in different amounts were tested inr limited quantities in W7yoming
and Montana. Only four of thtse, all of which contained 2.0 percent
of Piperonyl Cyclohexenone and 0.2 percent of pyrethrins, were found
to be at all effective against grasshoppers, and only one gave
encouraging results. This dust contained as diluents 60 percent of
Cohutta talc and 37.8 percent of other inactive ingredients. At 20
pounds per acre it gave knock-down of approximately 90 percent in 1
hour. The final mortality in 48 hours was 89 percent in one test
and 23 percent in a second one.

A dust containing the same amo-nts of Piperonyl Cyclohexenone
and pyrethrins was applied at the rate of 20 pounds per acre by Barnes
in Arizona. The mortalities recorded were 18 percent in 1 day, 22
percent in 3 days, and 29 percent in 6 days. A second trial with the
same dust at 40 pounds per acre gave 65-percent kill in 1 day and 74-
percent kill in 6 days. .hen a mixture of this dust with an equal
amount of a dust containing 50 percent of benzene hexachloride (5 per-
cent gamma isomer) was applied at the rate of 20 pounds per acre, the
results were equivalent to those obtained with the 50-percent benzene
hexachloride dust when used alone at the same rate.

SA3ADILLA

Sabadilla has been used for control of grasshoppers by growers in
Arizona. It was reported to be highly effective when applied at ex-
cessively high temperatures. In one test conducted by Barnes in Arizona,
20 pounds of a dust containing 4 pounds of ground sabadilla seed and 0.08
pound of sabadilla alkaloids was applied to a 1-acre plot with a power
duster. The temperature of the air at the time of application was 105F.,
that at the surface of open soil 136, and at the surface of shaded soil
108; the grasshoppers were all roosting on the tops of the alfalfa plants.
An estimated kill of 40 to 50 percent was obtained in 3 days.

HEXAETHYL TrhAPHOSPHATE

Hexaethyl tetraphosphate is miscible with water. Its chemical char-
acter, stability, and insecticidal efficiency may vary with the method
used in making it. It was tested only in California late in the season.





- 19 -


Wilson reported the results of a single test of a sample, obt;, ', 3I from
the Monsanto Chemical Co., in which it was applied at the rate of 2 pounds
per acre in 160 gallons of water. All the grasshoppers p,._ t at the
time were killed, and there was apparently some mortality of those which
moved into the sprayed area later. Severe burning of the i alfa foliage
was noted.

PHYTOTOXICITY

Applications of technical chlordane, methoxy analog of ben-
zene hexachloride, a chlorinated camphene ("3956"), and :J'.. ,ures of
Piperonyl Cyclohexenone and pyrethrins in dust did not give indi-
cation of injury to foliage. Emulsion-spray treatments of I po .id of
chlordane per acre to alfalfa just before and during bloor 1 ; did not
have any effect that prevented a good set of seed. One : Li of
chlordane or 4 pounds of a chlorinated camphene in 8 gallons of emul-
sion spray per acre did not damage the vegetation except e .j-
usually heavy applications were made, such as where a spral e, _.s
parked and aL-owed to drip onto the foliage. Emulsion spra,, .. :n-
taining the highest concentrations of the methoxy analog of D T or
benzene hexachloride tested caused noticeable burning, .'. this was
probably due to the large amounts of xylene which were necessf-- to
dissolve the insecticides. Spray applications of the type _Lzaethyl
tetraphosphate used, at 2 pounds per acre, caused severe bi ., '_ of al-
falfa in the quarter-bloom stage.

TOXICITY TO LIVESTOCK

In experiments conducted by Howard Welch and Hadlei .,
veterinarians at the Montana Agricultural Experiment Station, the
methoxy analog of DDT and benzene hexachloride were appa-1-,- ;13 no
more toxic to sheep and cattle than was DDT. The maximum safe
single dose of DDT for sheep was between 1 and 2 grams per 'Iilnram
of body weight; that for chlordane was less than 0.5 gram l kilo-
gram. Sheep grazed on pasture grass sprayed with chlorda.Ie at rates
up to 4 pounds per acre showed no apparent ill effects. It is known
that DDT is secreted, possibly in dangerous amounts, in "l mI t and
milk of animals which have ingested it with their feed, but it is not
yet known whether chlordane, benzene hexachloride, chlorinated cam-
phene, and hexaethyl tetraphosphate are similarly secreted I must
therefore be assumed that they may be dangerous in this respect, and
crops that have been treated with any of them should not be fed to
livestock until more information is available concerning tl.- residue
hazards involved.

SUMMARY

Several of the newer insecticides were tested against
hoppers in alfalfa in 1946, by members of the Bureau latorat Ies
at Bozeman, Mont., Tempe, Ariz., and Sacramento, Calif.





- 20 -


The most promising material tested was a chlorinated hydro-
carbon known as chlordane. The technical grade of this material
was used. To test this material as an emulsion, a stock solution
was prepared by dissolving chlordane in an equal quantity by volume
of xylene or No. 1 petroleum distillate. An emulsifying agent
(Igepal CA, a condensation product of ethylene oxide and alkylated
cresol) was added to this solution at the rate of 3.4 fluid ounces
per gallon of the mixture. This solution was diluted with water to
make 4 to 24 gallons of spray as needed in order to apply the de-
sired quantity of active ingredient per acre with the particular
equipment to be used. Tests were also made of dusts containing 2.5,
5.0, or 7.5 percent of technical chlordane.

In ail tests except one, in which a migration of hoppers onto
the plot obscured the results, technical chlordane in emulsion spray
at 1 pound per acre gave mortalities of 90 percent or better. Emul-
sion sprays were more effective than dusts at the same rate of appli-
cation. The several types of equipment used in the tests with sprays
and dusts apparently rrade no difference in the end results with either
dusts or sprays. In an Arizona test the residue from an emulsion
spray at 1 pound of technical chlordane per acre continued to kill
grasshoppers for at least 26 days. In South Dakota a similar spray
was effective for 10 days. Rain in South Dakota eliminated any residual
effect. The material apparently had no effect on a colony of honey-
bees placed in a sprayed plot a few hours after treatment. Other in-
sects essential to the setting of seed in alfalfa apparently were not
harmed when the fields were sprayed in the prebloom stage.

Benzene hexachloride containing 10 percent of the gamma isomer was
tested in emulsified and dust form. The stock solution used in pre-
paring emulsions contained 1 pound of the benzene hexachloride per
gallon of xylene with 3.4 fluid ounces of emulsifier (Igepal CA)
added. To this solution enough water was added to permit the appli-
cation of the desired dosage of active ingredient with the particular
equipment to be used. The dusts contained 10, 15, 30, 40, or 50 per-
cent of the benzene hexachloride in pyrophyllite or talc. Field
tests at 2 pounds per acre in an emulsion averaged approximately 70
percent kill in alfalfa. Field tests at 3 pounds per acre in an emul-
sion averaged 90-percent kill, but because of the large amount of sol-
vent (xylene) necessary to dissolve 3 pounds of the insecticide the
alfalfa plants were noticeably dama-ed. Three pounds in a dust
avera 'ed only 07-percent kiil. Suspension sprays also gave lower
kills than emulsions at equivalent dosages. Results with this material
were variable whether it was applied as a spray or as a dust. Dusts
applied by airplane gave slightly lower kills than those applied by
ground equipment. Slightly hiher kills were experienced withsprays
applied in the evening or during cool, damp weather. Continued kills
were noted up to 2 days with lighter dosages of the insecticide and
up to 6 days with excessively high dosa:-es. Some burning of foliage
was noted when excessive amounts of solvent were used, but in dusts
and suspension sprays excessive amounts of benzene hexachloride did
not damage foliage.





-21-


The technical grade of the methoxy analog of DDT, l-trichloro-2,2-
bis(p-methoxyphenyl)ethane, gave mediocre kills at all dosages up to
4.5 pounds per acre except in emulsions. At 3 pounds per acre in an
emulsion the average kill was 52 percent. At 4 pounds per acre in
the same-type spray it averaged 80 percent, but the excessive amount
of xylene necessary to dissolve the insecticide burned the foliage
noticeably. Dosages of as much as 4.5 pounds per acre in dust form
failed to give satisfactory kills. There was some evidence that it
was more effective at comparatively low temperatures.

A crilorinated camphene containing 67-69 percent of chlorine and
designated experimentally as Hercules 3956 was tested. The action of
this material on grasshoppers was observed in only a few late-season
tests at dosages of from 2 to 8 pounds per acre. It shows consider-
able promise as a spray or dust, but insufficient data have been ob-
tained to determine the optimum dosage.

Dusts containing Piperonyl Cyclohexenone and pyrethrins were
tested in Wyoming, Montana, and Arizona,but the results are insuffi-
cient at this time to warrant definite conclusions.

Sabadilla was tested in a limited way in Arizona under conditions
reported to be ideal. The resultant mortalities were between 40 and
50 percent.

One form of hexaethyl tetraphosphate was tested 4t 2 pounds per
acre in a dilute water spray in one trial in California. It gave 100-
percent kill of the grasshoppers present on the plot but burned the
vegetation severely.

None of the other materials tested showed any effect on vegetation,
except in the case of benzene hexachloride and the methoxy analog of
DDT where it was necessary to use a large amount of solvent (xylene).
If emulsions of these insecticides are to be used on alfalfa, it will
apparently be necessary to find a solvent less injurious to plants.

Limited experiments on the acute toxicity to sheep of the insecti-
cides tested for grasshopper control indicated the methoxy analog of
DDT and benzene hexachloride to be about as toxic as DDT and chlordane
to be from two to four times more toxic than DDT. Sheep grazed on
pastures sprayed with technical chlordane at rates up to 4 pounds per
acre showed no apparent ill effects. It is known that DDT is secreted
in the meat and Pilk of farm animals, but it is not yet known whether
the insecticides tested against grasshoppers in the experiments re-
ported in this paper are similarly secreted. Until more information
is available on this question, crops to which any of these insecticides
have been applied should not be used as feed for livestock.




UN IERSITY OP 138
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3 1262 09239 1381