December 1948 E-762
United States Department of Agriculture
Agricultural Research Adninistration
Bureau of Entomology and Plant Quarantine
THE NEW INSECTICIDES RDR CONTROLLING EXTE14AL PARASITES OF LIVESTOCK
By Division of Insects Affecting Man and Animals
Since 1945, when DDT first came into use for controlling insects
and ticks on livestock, severAl new insecticides have been developed
vhich are now available to the public for the control of those pests.
These insecticides are benzene hexachloride, chlordane, chlorinatLed cam-
phene, methoxychlor, TDE, and piperonyl butoxide. The Bureau of
Fitomology and Plant Quarantine has during this short period endeavored
to appraise the merits of these new materials for controlling various
external parasites of farm animals. Although there is need for further
investigations on the use of these new insecticides, the great Jemrnd
for information already obtained by the Bureau has prompted the issuance
of this preliminary report. Certain data obtained in cooperation with
other agencies are included.
The major objectives of this report are (1) to summarize the re-
sults of research which has been conducted to date and, insofar as
possible, to compare the performance of the different materials against
various livestock pests; (2) to summarize briefly the available knowl-
edge regarding the toxicity of the materials to animals; and (3) to issue
guiding statements as to how the new materials may be employed if their
use is warranted at this time. The Bureau is reluctant to offer such
guiding statements at this time, but the materials are available aid
are being used by livestock growers in some cases without regard to the
hazards involved and without the benefit of available knowledge re-
garding their effectiveness.
Because of the many insecticides and insecticide preparations
currently available to the public for the control of several livestock
pests, it is extremely important to determine which materials to employ
for maximum efficiency, safety, and economy. Consideration must be
given to the parasites involved, the types of animals, methods of ap-
plication, stability of specific formulations, and other factors.
IESUILTS OF TESTS WITH VPRTOUS INSECTICIDES
Benzene hexachloride has been tested rather extensively by State
and Federal agencies, commercial companies, and other institutions
associated with the livestock industry. It is generally available in
the form of wettable powders and dusts and less generally as solutions
and emulsion concentrates. The technical product consists of several
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isomers and usually contains 10 to 12 percent of the gamma isomer, which
is the most active one. Most wettable powders contain 50 percent of
technical benzene hexachloride, or 5 to 6 percent of the gamma isomer.
Some manufacturers are now producing grades that contain up to 95 percent
of the gamma isomer.
The insecticide is a crystalline product with a persistent musty
odor. This objectionable odor is less intense in some of the products
of high gamma content.
Wettable-powder preparations have been used in most of the tests,
but xylene emulsions have also been tested. In general no marked dif-
ference in effectiveness has been noted in the two forms. Benzene hexa-
chloride is a contact insecticide, but it also has some fumigating ac-
From the standpoint of initial killing action, benzene hexachloride
is among the most effective insecticides for controlling lice on cattle.
It kills the eggs as well as the motile forms by contact, and it also
acts as a fumigant.
Benzene hexachloride has been tested against the short-nosed cattle
louse (Haematopinus eurysternus (Nitz.)), the long-nosed cattle louse
(Linognathus vituli (L.)), and the tail louse (H. auadripertusus Fahr.).
Complete control of the first two species was obtained when animals were
thoroughly sprayed with 0.5 percent of technical benzene hexachloride
(0.05 to 0.06 percent of the gamma isomer) in wettable-powder sprays.
A single thorough treatment with 0.25 percent of the technical material
has given good control, but in tests conducted in Texas this concentra-
tion did not always give complete control. Both concentrations have given
good initial control of the tail louse in a limited number of tests. Ap-
parently complete control of this species has been obtained with a 1-
Wettable-powder and emulsion dips of technical benzene hexachloride
have been tested against red and yellow goat lice (Bovicola spp.) on
Angora goats. At 0.2-percent concentration a single dipping eliminated
lice from the herd. Excellent initial control was obtained with 0.05-
percent dips, but several months after treatment a few lice were present.
DDT at the same concentrations has given similar results.
Benzene hexachloride is also effective against the hog louse
(Haematopinus adventicius Neum.). A single thorough treatment with
0.2 percent of the technical material has given good but not complete
control in a limited number of tests. Other workers have reported com-
plete control at 0.5-percent concentration.
In Oregon dips containing 0.05, 0.2, and 0.5 percent of technical
benzene hexachloride have provided complete control of the sheep tick
(Melophagus ovinus (L.)). Thorough treatments with 0.2-percent sprays
(4 to 6 quarts per mature sheep with long fleece) were effective in
limited tests, but complete control was not effected until several weeks
after treatment. Ground derris (rotenone 5 percent), at rates of 4 and
8 ounces in 100 gallons of dip, also gave complete control of this in-
sect. Hotenone as a dip seems to be the most economical treatment for
controlling this pest, and from this standpoint is superior to any of
the new insecticides.
Lone S Tick
Benzene hexachloride has been tested against the lone star tick
(Amblyomia americanum (L.)) on cattle at concentrations from 0.1 to
1.5 percent of the technical product. It has killed all stages of the
tick at concentrations as low as 0.25 percent. However, even at 1.5
percent the residual action has not been marIked. At Kerrville, Tex.,
a 0.5-percent spray protected animals for about 4 days, but after 1
week some ticks were beginning to engorge. Concentrations higher tUlan
0.5 percent did not seem to prolong the protection to any marked degree.
In comparative tests DDT failed to kill all engorged ticks at a concen-
tration as high as 1.5 percent. However, DDT provided better protec-
tion against reinfestation than did benzene hexachloride. After 2
weeks the control obtained with sprays containing 0.5 and 0.75 percent
of DDT was comparable with that obtained after 1 week with similar
concentrations of benzene hexachloride. The 0.75-percent DDT spray
provided about 75 percent protection for 2 weeks.
Sprays containing benzene hexachloride have been tested on cattle
and sprays or washes on horses for control of the winter tick (Dermacentor
albipictus (Pack.)) in the vicinity of Kerrville. Good control of all
stages resulted at a concentration as low as 0.1 percent of technical
benzene hexachloride. Concentrations of 0.25 and 0.5 percent protected
animals against reinfestation for about 2 weeks. DDT emulsions and wet-
table powders failed to kill all engorged ticks at concentrations up
to 2.5 percent, but 0.5-to 0.75-percent concentrations provided pro-
tection for about 4 weeks.
In laboratory and field tests benzene hexachloride was effective
against the ear tick (Otobius meanini (Dages)) when applied as a spray.
However, little is known about the most practical concentrations re-
quired to control this species or about the duration of effectiveness.
Benzene hexachloride is highly toxic to the horn fly (Siphona
irritans (L.)) and the house fly (Musca domestic L.), but its residual
action is not sufficient to effect lasting control. Sprays applied on
cattle for the control of horn flies at concentrations of 0.25 to 0.5 per-
cent generally become ineffective in 3 to 4 days as compared with 3 to
4 weeks for DDT. In laboratory tests conducted at Orlando, Fla., de-
posits of benzene hexachloride up to 400 mg. per square foot failed to
give complete control of house flies exposed for 2 hours 9 weeks after
treatment, whereas DDT applied at rates from 50 to 400 mg. per square
foot was completely effective at the end of 36 weeks.
Benzene hexachloride has been reported to provide some control of
norse flies and deer flies. In tests conducted in Texas against
TobFnus abrctor Philip, all flies feeding on treated cattle for 1 to
2 days after spraying were killed. In Georgia some success against
tnbanids was indicated with mixtures of benzene hexachloride and methoxy-
chlor. The destruction of tabanids that feed on treated animals during
the indicated short period of effectiveness might reduce the population
sufficiently to provide some control. However, further study is nec-
essary to determine the value of benzene hexachloride in practical con-
trol of these pests.
Screw-Worm and fleece Worms
Benzene hexachloride is highly effective as a larvicide for the
screw-worm (Callitroga americana (C. and P.)) and fleece worms (Phormia
regina (Meig.) and other secondary blow flies). However, insufficient
tests have been conducted to determine its value as a practical con-
Common Cattle Grub
Benzene hexachloride in certain tests has given some kill of the
common cattle grub (Hypodemg lineatum (De Vill.)). Its perfo nuance is
erratic, however, and available formulations cannot be depended upon
to provide satisfactory control at concentrations that are considered
feasible from the standpoint of economy or safety.
Chlordane has been employed extensively for the control of certain
household pests. It is a viscous liquid, readily soluble in a number of
solvents, including petroleum oils. Recently chlordane has been offered
for sale for the control of various livestock pests. Rather extensive
tests have been conducted with this insecticide against most of the
Tiajor pests of livestock. Both a wettable-powder preparation and
emulsions have been used. Under some conditions chlordane exhibits a
fumigating property in addition to its usual contact action.
Chlordane, in both wettable-powder (50 percent) aid emulsion-
concentrate (25 to 50 percent) formulations, has been compared with
DDT against several species of lice on cattle. It is indicated to be
equal to DDT for controlling these insects. Complete control of both
long-nosed and short-nosed lice was obtained with 0.5-percent sprays.
A 0.25-percent spray gave good but not complete control of lice with
one treatment. The tail louse also appeared to be equally as sus-
ceptible to chlordane as to DDT. The concentration needed for prac-
tical or complete control has not been determined, buta 1-percent chlor-
dane spray gave complete control in one test.
Chlordane and DDT were found to be equally effective against red
and yellow goat lice in tests conducted in Texas. A 0.2-percent dip,
prepared from either wettable powder or emulsion concentrate, provided
complete control, and no reinfestation occurred for at least 4 months.
At 0.05-percent concentration both materials controlled all motile
forms, but some animals were found infested when examined 4 months later.
In one test with a few animals chlordane gave apparently complete
control of hog lice when applied as a wettable-powder spray at 0.2-
percent concentration. DDT in the same test gave good initial control,
but a few lice were found after 3 weeks.
Dips containing 0.05, 0.2, aid 0.5 percent of chlordane gave com-
plete control of sheep ticks. DDT also gave complete control, but
chlordane eliminated the emerging adults more quickly. When applied
as a spray at 0.2-percent concentration, chlordane was superior to DDT
and comparable with benzene hexachloride.
Lone Star Tick
Chlordane has been tested against the lone star tick on goats and
cattle at concentrations of 0.25, 0.5, 0.75, and 1.5 percent. All con-
centrations gave complete or almost complete control of the flat stages,
aid the 0.75- and 1.5-percent concentrations caused nearly complete kill
of all stages. DDT failed to kill all the engorged forms at 1.5-per-
cent concentration. At the same concentrations the two insecticides gave
about equal protection against reinfestation. (The performance of DDT
in these tests has been mentioned in the discussion of benzene hexa-
chloride for tick control.)
Chlordane is distinctly superior to DDT against the inter tick on
cattle and horses. Complete or nearly complete control of all stages
has been obtained with 0.75-percent sprays, whereas DDT st 1.5 percent
killed only a small percentage of the engorged forms. Chlordane is also
superior to DDT from the standpoint of protection against reinfestation.
At 0.5 and 0.75 percent chlordane prevented reinfestation for about 2
months as compared with 1 month for DDT. Chlordane as a 5-percent dust
has also given good control of winter ticks and proved superior to DDT.
Chlordane has been tested on animals exposed to horn flies in cages,
and in field tests on dairy animals in Texas and beef animals in Kansas.
The tests in Kansas were conducted in cooperation with the experiment
stations and State colleges of Kansas and Missouri, and with the Livestock
Loss Prevention Board of Kansas City. Wettable-powder sprays at concentra-
tions of 0.25 and 0.5 percent, applied at approximately 2 quarts per mature
animal, gave good control of horn flies and protected the animals for
about 3 and 4 weeks, respectively. There was no clear-cut difference in
effectiveness between DDT and chlordane, but chlordane appeared to be
Chlordane is more toxic than DDT to house flies. Its residual ac-
tion is long lasting but not equal to that of DDT. In laboratory tests
at Orlando, Fla., surface treatments at the rate of 200 mg. of chlordane
per square foot, applied in acetone solution, gave complete or almost
complete kill of flies exposed for 2 hours as long as 28 weeks after
treatment. DDT, however, was still completely effective after 36
weeks, even at the low rate of 50 mg. per square foot. Recently, reports
of failure of DDT to control house flies have been received. Limited
field tests have shown promise for chlordane as a substitute for DDT in
Chlordane applied as a 1- to 2-percent emulsion was effective for
about 1 day against tabanids feeding on treated livestock.
Screw-Worm and fleece W s
Chlordane is one of the most effective insecticides tested against
screw-worm larvae, and it also protects sheep from attack by fleece
worms. However, insufficient tests have been conducted to determine its
potential uses for controlling these insects.
Common Cattle Grub
When emulsion and wettable-powder formulations containing up to 1.5
percent of chlordane were applied to cattle, both as a wash and with a
high-power sprayer, the mortality of cattle grubs was less than 20-per-
cent. Dusts containing up to 5 percent of chlordane also proved in-
Technical chlorinated canphene is a waxy, crystalline material.
It has no objectionable odor, and is readily soluble in most of the
common solvents used in insecticide formulations, including petroleum
oils. It is one of the newest insecticides being offered to the public
for livestock-pest control. In most of the tests wettable-powders and
emulsion concentrates were used. The wettable powders contained from
25 to 40 percent of the toxicant, and the emulsion concentrate from 25
to 65 percent with xylene or kerosene as the solvent.
When tested at concentrations of 0.25 and 0.5 percent, chlorinated
camphene gave results that were comparable with those obtained with DDT,
benzene hexachloride, and chlordane against both short- and long-nosed
cattle lice and the tail louse.
Chlorinated camphene appeared to be at least equal, and perhaps
superior, to DDT, chlordane, end benzene hexachloride against red and
yellow goat lice. In limited tests apparently complete control was ob-
tained with dips containing 0.05 percent or a slightly lower concentra-
tion of the insecticide. Dips at 0.2-percent concentration have kept
goats free of lice for at least 4 months.
Only one test, involving a few animals, has been run with chlorin-
ated camphene against the hog louse. A wettable powder at 0.2-percent
concentration gave apparent complete control of the lice, being superior
to MDT and comparable with chlordane.
Against the sheep tick chlorinated camphene appeared to be superior
to wT when used as either a dip or a sprar, but less effective than
benzene hexachloride and chlordane. In a few tests complete control was
obtained with dips containing 0.05, 0.2, and 0.5 percent of the insecti-
cide. However, its action appeared to be slower than that of the other
Lone Star Tick
Chlorinated canphene proved superior to DDT and equal to chlordane,
but less effective than benzene hexachloride, against the engorged forms
of the lone star tick. Its residual effect provided protection against
reinfestation comparable with that given by DBT and chlordane. Sprays
at 0.75-percent concentration gave good control of all stages and pro-
tection against reinfestation for 2 weeks, comparable with that given
by DDT aid chlordane.
Chlorinated canphene was superior to DDT and comparable with chlor-
dane against the winter tick on cattle and horses, when employed either
as a spray or as a dust. Good control of all stages was obtained with
sprays containing as little as 0.75 percent. This concentration pro-
tected against reinfestation for about 2 months. A 0.5-percent sprey
failed to control all the engorged forms, but prevented further rein-
festations for 6 to 8 weeks.
Chlorinated camphene was superior to DDT and comparable with chlor-
dane and benzene hexachloride for controlling the ear tick. However,
further studies are needed to determine its value for this purpose.
Chlorinated canphene at 0.5-percent concentration has given results
similar to MDT for the control of horn flies. Although it is somewhat
slower in killing flies coming to treated animals, and under certain
conditions might appear to be inferior, final control has in general
been comparable with that obtained with DDT.
Chlorinated camphene was less effective than DDT against house
flies, from the standpoint of'both initial killing action and residual
action. Little information is available on the relative efficiency of
the two materials against stable flies. Chlorinated camphene did not
protect animals from attack by tabanids.
Screw-Worm and Fleece Worms
Chlorinated camphene was highly effective against young screw-worm
larvae and the larvae of fleece worms. It provided excellent protection
against fleece worm attack on sheep, when used at 2-percent concentration.
However, little is known about the value of this material for controlling
either of these parasites under practical conditions.
Common Cattle Grub
In small-scale tests chlorinated camphene did not control larvae
of the common cattle grub.
Methoxychlor (also called the methoxy analog of DDT) is similar to
DDT in both physical and chemical properties. Most of the tests have
been made with 50-percent wettable powders aid 25-percent emulsion con-
centrates, in general with equal effectiveness.
Sprays containing 0.5 percent of methoxychlor gave good control
of short-nosed and long-nosed cattle lice aid the tail louse in some#
but not all tests.
Methoxychlor was effective against the hog louse and perhaps com-
parable with DDT, but a single treatment with 0.2-percent spray did not
give complete control.
Against ticks methoxychlor was less effective than the other chlorin-
ated hydrocarbon insecticides. Wettable-powder sprays up to 1.5 percent
did not kill unengorged and engorged winter ticks and lone star ticks
on cattle and horses and animals became reinfested by the second week.
In laboratory dipping tests it was inferior against the lone star tick
and the ear tick. In tests in Oregon, however, it controlled sheep
ticks when employed as a dip at 0.2- and 0.5-percent concentrations.
Methoxychlor gave good control of the horn fly on cattle. A 0.5-
percent wettable-powder spray (2 quarts per mature animal) applied to
dairy cattle in Texas and to beef cattle in Kansas provided 20 to 24
days' protection, as compared with 28 to 30 days for DDT. In Missouri
both materials protected animals for about 6 to 7 weeks. Tests on treat-
ed animals exposed to flies in cages indicate that this material is
slightly inferior to DDT.
In laboratory and small-scale field tests methoxychlor was effec-
tive against house flies and stable flies. Although generally its
residual effectiveness was of shorter duration, under certain conditions
it was superior to DDT. Preliminary tests in Texas and in Georgia in-
dicate that this insecticide, alone and with benzene hexachloride, offers
some promise in controlling tabanids.
TYE (also called DDD) is a crystalline substance closely related to
DDT in chemical and physical properties. The types of formulations used
are also similar to those of DDT. Tests conducted with both emulsion
and wettable-powder formulations have thus far shown no difference in
TDE was about equal to the other chlorinated insecticides for the
control of short-nosed and long-nosed cattle lice, and also of the tail
louse. A 0.5-percent spray thoroughly applied gave good control of the
first two insects.
In preliminary tests run on a few hogs for the control of the hog
louse, TDE was equal to DDT in initial kill. Neither material gave
complete control at 0.2-percent concentration.
TDE gave good control of sheep ticks when employed as a dip at
concentrations of 0.2 and 0.5 percent. It was about equal to'methoxy-
dhlor but less effective than the other chlorinated hydrocarbon insecticides.
In laboratory dipping tests against the lone star tick TDE was
not so effective as chlordane, benzene hexachloride, chlorinated camphene,
In a limited number of tests against the winter tick TDE was approxi-
mately equal to DDT but inferior to chlorinated camphene snd chlordane.
Sprays containing 0.5 to 0.75 percent of TDE did not kill engorged ticks
but prevented reinfestations for about 1 month.
TDE gave satisfactory control of horn flies on beef and dairy ani-
mals. In general at 0.5-percent concentration (in a wettable powder)
this material was about equal to methoxychlor and slightly less effective
than DDT and chlorinated camphene.
In laboratory tests TDE was less effective than DDT against house
flies and stable flies.
Piperonyl butoxide alone is somewhat insecticidal, but it is of
chief interest for use in combination with pyrethrum, which is widely
used in cattle fly sprays. The insecticidal action of pyrethrum is
rapid and it is safe for use on warm-blooded animals, but it is cost-
ly and is unstable. The addition of piperonyl butoxide to pyrethrum
increases the insecticidal action, and the duration of its effective-
Emulsions containing 0.005 percent of pyrethrins and 0.05 percent
of piperonyl butoxide, or 0.01 percent of pyrethrins and 0.1 percent of
piperonyl butoxide, gave complete initial control of the short-nosed
cattle louse, but young lice were present on the treated animals after
The pyrethrum-piperonyl butoxide sprays provided considerable pro-
tection to animals against stable flies for several days. Some pro-
tection against tabanids was also indicated, although results reported
by several investigators vary considerably with respect to duration of
protection against different species. Not enough research has been
conducted for conclusions to be drawn regarding their effectiveness
against livestock pests in general.
The Fbod and Drug Administration is investigating the toxicity of
the various new insecticides to laboratory animals. The Bureau of
Entomology and Plant Quarantine, in cooperation with the Bureau of
Animal Industry and the Texas Agricultural Experiment Station, is con-
ducting certain toxicological studies on livestock.
- 11 -
The references to the toxicity of the insecticides to small labora-
tory animals are taken from a recent paper by A. J. Lehman j/, pharmacolo-
gist in the Food and Drug Administration. The data represent general aver-
ages for several kinds of laboratory animals. Since most of the studies
are incomplete, and many of the formulations differed from those employed
in treating livestock, the information indicates trends or approximate
The Bureau is conducting toxicological investigations (1) to deter-
mine the effects on livestock of various materials when applied external-
ly and (2) to determine the amount of insecticide secreted in milk when
applied to dairy animals in amounts and frequency necessary to control
horn flies. The tests on livestock are being conducted at Kerrville,
Tax., and the chemical analyses at Beltsville, Md. Some studies have
also been made to determine whether products from animals treated with
benzene hexachloride are tainted with its odor or taste. Investigations
on absorption and storage of insecticides in animal tissues resulting
from external treatments are under way, but insufficient data are
available to include them in this discussion. Chronic-toxicity studies
involving repeated treatments of livestock with the various insecticides
over a period of years have not been undertaken.
The different isomers of benzene hexachloride vary in their toxi-
city to higher animals. Fbr the ganma isomer the mean lethal dose to
laboratory animals, when administered by mouth, is approximately 125 mg.
per kilogram of body weight, as compared with about 250 mg. for MDT.
In oil solution it is readily absorbed through the skin; when it is ad-
ministered in this way the mean lethal dose to laboratory animals ranges
from 20 to 50 mg. per kilogram. On daily feeding gmnma benzene hexa-
chloride is less toxic than DDT but it is much more toxic when applied
to the skin.
At Kerrville high concentrations and frequent treatments were
tested to gain information on the upper limits of toxicity. When mature
or near mature animals were employed, no harmful effects were noted
on 8 sheep, 8 goats, 4 cattle, 2 horses, and 2 hogs treated eight
times at 4-day intervals with a dip or spray containing 1.5-percent
of technical benzene hexachloride. A wettable-powder. preparation was used
on some of the animals and a xylene emulsion on the others. The Livestock
Loss Prevention Board of Kansas City obtained similar results on 8
animals treated with a wettable-powder spray at the same concentration.
At Kerrville 10 cows treated nine times at 2-week intervals with a 2-per-
cent wettable-powder spray were without apparent harmful effects. However,
when a wettable powder containing 50-percent of gamma benzene hexachloride
was used, all 3 cattle treated once with a spray containing 1.5 percent
of the gamma isomer were killed, and 1 out of 3 sprayed with
_/ Lehman, A. J. The Toxicology of the New Agricultural Chemicals.
Bul. Assoc. Fbod and Drug Officials 12(3): 82-89. 1948.
0.75-percent gamma died and another was seriously affected but recovered.
A 0.25-percent gamma spray had no ill effects.
Calves less than 3 months old are much more susceptible to benzene
hexachloride than are cattle a year old or older. Xylene-emulsion sprays
containing 0.05 percent of the gamma isomer killed some calves that were
thoroughly saturated to simulate dipping. Wettable-powder sprays of the
sa-e gamma content were apparently less toxic, but toxic symptoms were
evident in two of nine calves treated and one calf died. Few reports
of 1-tb or injury among calves or cattle have been received following
trti -.- with' benzene hexachloride in actual use for pest control.
Hcizv thks- available toxicology data suggest that the margin of
s.- ety for benzene hexachloride applied to young calves is extremely
ri ar row.
? *ete-Qi d whether the use of benzene hexachloride gave off-flavor
or c* t.-. of treated animals, tests were conducted with several
. A *' "-.z .One piot received two thorough treatments 9 days apart
.', a c'o" t r ,i -iirg 2.5 percent of technical benzene hexachloride.
:-.,rs -r'e- the -eond treatment 10 families cooked and tasted the
ne ". ,', -familie-. dt-'!ct"ec benzene hexachloride taste, but
2o-i *.-. ,--' ed th-. -or whi-le the meat was cooking. Another pig
s c-e 4 ys *L.r!t r ith 1.5-p5ercent technical benzene hexa-
.r.-*:e, and s' :,\.. sired on the sixth day. None of the families eat-
*:--,eat re,.rt.ed benzene hexachloride odor or taste. In similar
S-th w :z':t, a cheep, a-.d a yearling calf one report of benzene
hieeaehio :e, favor or odor from each animal was received. Another
calf tFrd a t-, treated eight times at 4-day intervals with a 1.5-per-
3. and sl.-htered 1 month after the last treatment showed no
r.-.ei off-flavor or odor, although some individuals gave positive re-
p,:"'s. In tests with six chickens exposed for one to several weeks to
roo'-.s heavily painted with a slurry of technical benzene hexachloride,
conflicting reports were received but in one chicken marked benzene
h->..:.cloride odor was detected.
In these tests the concentration of benzene hexachloride was in
exce-,- of that needed for controlling the parasites. In a thorough
test conducted in cooperation with the Missouri Agricultural Experiment
S'P.t. on and College, no off-flavor or odor was detected in meat from a
cow dipl.-J ap)r-r,7xrT.tely 1" times during the course of 2 years in a wet-
:e--;-'. dedip containing 0.5 percent of technical benzene hexachloride.
No -epcrt, of off-flavor or odor of meat from livestock treated with
ben;ne heixa hloride for practical pest control have come to the atten-
tion of this Bureau.
The acute toxicity of chlordane administered orally to laboratory
animals was found to be about half that of DDT. However, the toxicity
of a solution n applied repeatedly to the skin is reported to be greater
At Kerrville five sheep, five goats, two cattle, and one horse
were treated eight times at 4-day intervals with a 1.5-percent chlordane
emulsion, anid the same numbers of animals were treated with a wettable-
powder preparation at the same strength. The test was repeated with a
new lot of chlordane, but only five sheep and two pigs were treated
with each preparation. In the first test none of the cattle or horses
were killed with either preparation, but the sheep and two of the goats
were killed by the emulsion and two sheep and two goats by the wettable
powder; some of the animals died after the third treatment. In the
second test none of the animals were killed.
The Livestock Loss Prevention Board obtained similar results in
that sheep were killed by the severe treatment, and one of two cattle
sprayed with the emulsion and with the wettable.,powder suspension was killed.
In another test at Kerrville three of ten cattle died after four
thorough treatments at 2-week intervals with a 2-percent wettable-
powder preparation. No explanation can be offered for the variable
Weekly analyses of milk samples from two dairy herds sprayed four
times with 0.5-percent wettable powder at intervals of about 1 month
showed that small amounts of organic chlorine were present in the milk.
Of 18 samples analyzed, 17 showed from 0.1 to 0.4 p.p.m. of organic
chlorine. However, it is not certain that all the organic chlorine
present can be attributed to the chlordane treatment.
Chlorinated camphene was found to be about four times as toxic
as DDT when administered orally to various laboratory animals. The
mean lethal dose of chlorinated camphene, when administered orally to
laboratory animals, was about 60 mg. per kilogram. Preliminary tests
indicate that livestock are of similar susceptibility. When applied to
the skin it is also far more toxic than DDT. Although the insecticide
is rather toxic from an acute standpoint, preliminary chronic-toxicity
studies reported by the Food and Drug Administration indicate that for
certain animals the insecticide taken in the diet in small doses over
an extended period of time is not so toxic as certain other insecticides
that are more toxic on the basis of single acute doses.
When 20 sheep, 15 goats, 8 cattle, 4 horses, and 4 hogs, all mature
or nearly mature, were treated eight times at 4-day intervals with 1.5
percent of chlorinated camphene,no adverse effects were noted on any
of the animals.
However, young calves are more susceptible to this insecticide.
After reports of its toxic effect on calves in Texas, tests were made
on calves 1 to 2 months old. A single spraying with 1.5-percent emul-
sion (containing xylene and kerosene) or wettable-powder -.:sperlsion
caused toxic symptoms on some of the treated calves, and two treatments
4 days apart caused a few deaths. Single treatments of 0.75-percent
concentration had no adverse effects on 12 calves.
Milk samples from dairy herds treated four times at about monthly
intervals with 0.5-percent wettable-powder sprays were analyzed for
organic-chlorine content. Of 43 samples analyzed, 27 were negative.
When the results were positive, the amounts of organic chlorine ranged
from 0.2 to 0.6 p.p.m. It is not certain that the organic chlorine
present can be attributed to the chlorinated cauphene.
Methoxychlor is the least toxic of the chlorinated hydrocarbon
insecticides that have been investigated. The mean lethal dose to
various laboratory animals when administered orally was about 6 per
kilogram of body weight. Preliminary feeding tests also suggest a
low chronic toxicity.
At Kerrville no adverse effects were noted when five sheep five
goats, two cattle, two hogs, and one horse were treated eight times
at 4-day intervals with an emulsion containing 1.5 percent of
Milk samples collected at weekly intervals from two herds of dairy
cattle treated with a 0.5-percent wettable-powder suspension five and
six times during the season were analyzed for organic-chlorine content.
Only 3 of 42 samples analyzed showed organic chlorine (0.1 p.p.m.)
The average mean lethal dose of TDE for several laboratory animals
was about 2,500 mg. per kilogram of body weight when the insecticide
was administered orally. Preliminary feeding tests indicate that the
chronic toxicity of TIE is also considerably less than that of DDT.
At Kerrville five sheep, five goats, two cattle, two hogs, and
one horse showed no ill effects when treated eight times at 4-day in-
tervals with 1.5-percent emulsion or wettable-powder preparation.
Samples of milk taken at weekly intervals from two herds of dairy
cattle treated with TDE were analyzed for their TDE content by the
colorimetric method. The animals had been treated five times with a
0.5-percent wettable-powder spray (approximately 2 quarts per animal).
Of 20 samples analyzed, 8 were negative and 12 showed TDE present in
amounts ranging from 0.1 to 1.2 p.p.m., the average being less than
In comparison, all milk samples (total of 26) from herds sprayed
with 0.5 percent of DDT contained DDT. The amounts ranged from 0.1 to
2 p.p.m., with an average of about 0.6 to 0.7 p.p.m. When 0.25-percent
spray was used, the amount of DDT in the milk ranged from 0.1 to 0.7
The mean lethal dose of piperonyl butoxide administered by mouth
to various laboratory animals was about 12 grams per kilogram of body
weight. Its acute toxicity was the lowest for all the insecticides.
Pyrethrum, with which this material is usually combined, alone was also
relatively nontoxic to warm-blooded animals.
SUGGESTIONS REGARDING THE USE OF THE NEW INSECTICIDES
Suggestions regarding the use of the new materials offered at this
time are not necessarily final recommendations. The preliminary nature
of the available information regarding their toxicity and performance
does not permit definite conclusions to be drawn at present. Livestock
growers who contemplate using any of the new materials should follow
the recommendations of agricultural workers who are familiar with live-
stock-pest problems in experiment station, State colleges, and ex-
tension services of their State or community.
If benzene hexachloride is to be used for controlling any livestock
pests, it is recommended that only wettable-powder formulations be used.
Products of high gamma-isomer content are the least objectionable from
the standpoint of odor. This insecticide should not be applied on
dairy animals or on meat animals that are to be slaughtered within 30
days. In view of its toxicity, particularly to young animals, the con-
centration should be held down preferably to 0.25 percent of the tech-
nical material (0.025 percent of gamma isomer) and should not exceed
0.5 percent even when applied to older animals.
No harmful effects on livestock have been noted or reported when
chlordane has been applied in insect-control operations. However, since
toxic effects have developed in experiments with 1.5-to 2-percent spray
applied repeatedly to livestock, additional tests with repeated treat-
ments at lower concentrations should be conducted before recommendations
are made for its use on livestock.
Chlordane shows promise for use against house flies in situations
where adequate control cannot be obtained with WDT.
From the standpoints of economy and efficiency chlorinated camphene
is considered promising for the control of a number of livestock pests.
However, some deaths of animals, principally young calves, have b--een
reported when this insecticide has been employed in insect-conLrol -prra-
tlons. Since the concentrations required for controlling certain live-
stock pests are near the toxic level for young animals, further investi-
gations should be conducted with various formulations applied to faru
animals of various age groups before suggestions are offered regarding
its use against livestock pests.
UNIVERSITY OF FLORIDA
3 1262 09239 2165
e i,!ioxy chl or
'-e Tow ..ox ci'-,7 o 1 *coi' chlor to animals is an important point
in favor of this ins-.' ...i- Je. Its acute toxicity is much lower than
.h-t of other chlornn-n:.i hydrocarbon insecticides. Furthermore, little
or non-. of the material is secreted in milk of treated dairy cattle.
Its use is therefore encouraged for controlling insects on dairy animals.
Results to date indicate that for horn flies and lice on cattle the
insecticide compares rather favorably with other available materials.
It is suggested that cattle be treated with a 0.5-percent spray. For
control of horn flies about 2 quarts of this spray should be applied to
a mature animal. Fobr control of lice from 2 to 6 quarts is recommended.
Against horn flies about 3 to 31 weeks' protection may be expected as
compared with about 4 weeks for D3E applied at the same rate. The high-
er price of the insecticide and possible shorter period of protection
may discourage its use on range animals.
Methoxychlor may be considered for controlling house flies under
conditions where DDT has not given satisfactory control.
Although less toxic to animals than DDT, more information is needed
on the effectiveness of TDE before it can be recommended for controlling
certain livestock pests. The insecticide does provide satisfactory con-
trol of horn flies and lice on cattle. For this purpose a concentration
of 0.5 percent is suggested.
Piperonyl Butoxide-Pyrethrum Insecticides
Because of the low toxicity of piperonyl butoxide-pyrethrum in-
secticides to animals no hazards should ordinarily result from its use.
For protection of dairy animals this insecticide preparation should be
considered for control of lice, horn flies, stable flies, and tabanids.
However, the Bureau does not have sufficient information at this time
to suggest the best concentrations to use.