The new insecticides for controlling external parasites of livestock

LIBRARY
STATE PAIA*Ti1ARD E-762 (Revised)

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



THE NEW INSECTICIDES FOR CONTROLLING
EXTERNAL PARASITES OF LIVESTOCK

By the Division of Insects Affecting Man and Animals


A report on the new insecticides for controlling external parasites of
livestock (E-762) was first issued in December 1948. The publication
briefly reviewed the available information on the insecticidal efficiency
and toxicology of DDT, benzene hexachloride, chlordane, toxaphene
(chlorinated camphene), TDE, methoxychlor, and piperonyl butoxide.
Suggestions regarding uses for the new materials were also offered.
Recently new information has been obtained by the Bureau of Entomology
and Plant Quarantine, the Food and Drug Administration, and others,
which necessitates-some changes in recommendations and suggestions
relative to the use of DDT and the newer materials when applied to live-
stock. This report is therefore issued as a revision of and a replacement
for the original publication E-762.
The major objectives of this report are (1) to summarize the results
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 knowledge re-
garding the toxicity and potential hazards of the materials to man and
animals; and (3) to recommend or suggest restrictions and specific uses
for the new materials, including DDT.
So many insecticides and insecticide preparations are involved that it
has not been possible to investigate them thoroughly for their many
potential uses. For this reason it is difficult at this time to determine
with finality which materials and formulations to employ for maximum
efficiency, safety, and economy. Before such conclusions can be reached,
consideration must be given to the parasites involved, types and age of
animals, methods of application, stability of specific formulations, climatic
conditions, and other factors. Further research on the various new
materials, including those not recommended at this time, is under way
by several agencies, and as more information is obtained changes in
current recommendations or suggestions may become necessary or
desirable.


UBRARY
STATE PLAN BOARD






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RESULTS OF TESTS WITH VARIOUS INSECTICIDES

In this summary of the results obtained with the various new insecti-
cides against different livestock pests, the performance of DDT will not
be discussed under a separate heading. Most of the information obtained
by various investigations on this insecticide has been published. However,
DDT will serve as a basis for comparing the performance of the new in-
secticides.
The data obtained on the performance of the various insecticides are
discussed, even though some of the materials are not recommended for
livestock-pest control and certain restrictions are recommended for
others.

Benzene Hexachloride

Technical benzene hexachloride as manufactured consists of several
isomers The gamma form is the most effective against insects and other
external parasites. When benzene hexachloride first became commercially
available, most manufacturers formulated insecticides made from the
technical product containing 10 to 12 percent of the gamma isomer. The
50-percent benzene hexachloride wettable powder contained 5 to 6 per-
cent of the gamma isomer. Recently there has been a trend in industry
to produce benzene hexachloride of higher gamma content, and some
manufacturers are producing benzene hexachloride containing from 95
to 98 percent of the gamma isomer. With the development of benzene
hexachloride of higher gamma content there has been a corresponding
trend toward the formulation of wettable powders containing more of the
gamma isomer.
The Bureau's tests have dealt chiefly with the wettable-powder
preparations of benzene hexachloride, but xylene emulsions have also
been tested. In general, both types of formulations have been equally
effective. Tests have been made against a number of livestock pests
with benzene hexachloride samples of varying gamma-isomer content.
In general, it appears that the practical insecticidal effectiveness is due
almost entirely to the gamma isomer.
All the isomers of benzene hexachloride are crystalline products.
As originally produced, it had a persistent musty odor which was due
largely to forms of benzene hexachloride other than the gamma isomer.
The objectionable odor is much less evident in the newly developed
products of high gamma content.
In the discussion of tests with benzene hexachloride the concentrations
employed are for the most part expressed in terms of the gamma isomer,
whether a technical product or one of high gamma-isomer content was
used.





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Cattle Lice

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
Q.inognathus vituli (L.)), and the tail louse (H. quadripertusus Fahrz.).
Complete control of the first two species was obtained when animals
were thoroughly sprayed with 0.06 percent of the gamma isomer (0.5 per-
cent of technical benzene hexachloride containing 12 percent of the gamma
isomer) in wettable-powder sprays. A single thorough treatment with
0.03 percent of the gamma isomer has given good control, but in tests
conducted in Texas this concentration did not always give complete con-
trol. Both concentrations have given good initial control of the tail louse
in a limited number of tests. Apparently complete control of this species
has been obtained with a 0.12-percent spray.

Goat Lice

Wettable-powder and emulsion dips of benzene hexachloride have
been tested against red and yellow goat lice (Bovicola spp.) on Angora
goats. At 0.025-percent concentration of gamma isomer a single dipping
eliminated lice from the herd. Excellent initial control was obtained with
0.006-percent dips, but several months after treatment a few lice were
present. DDT dips at 0.2 -percent concentration have given complete
control of those lice.

Hog Louse

Benzene hexachloride is also effective against the hog louse
(Haematopinus adventicius Neum.). A single thorough treatment with
0.025 percent of the gamma isomer in the form of a wettab!v-powder
spray has given good but not complete control in a limited number of
tests. Other workers n1ave reported complete control at 0.05 to 0.06
percent concentrations.

Sheep Tick

In Oregon benzene hexachloride wettable-powder dips containing
approximately 0.006, 0.025, and 0.06 percent of the gamma isomer have
provided complete control of the sheep tick (Melophagus ovinus (L.)).
Thorough treatments with 0.025-percent wettable-powder sprays (4 to 6
quarts per mature sheep with long fleece) were effective in limited tests,









p ,-,- no-,t .ec aed ,.,"': several weeks r treatment.
Grown: deris (,-oh'.:;,ne 5 .-ircent), at rates of 4 and 8 ounces in 100
'_-. '... o <,_', also gave complete control of this insect. R.otenone as a
'i' seems to h-- the r' >st economical treatment for controlli;.. this pest,
and from this standpoint is superior to any of the n.?w insecticides.

Lone Star Tick

-: rzene hexcchloride ettabl1-power as well is emr'il:-.ion sprays
have been tesie ;c -..' :st the lone star tick (Amblyommrna americanum (L.))
on cattle at .-nmm a-isomer cer er,-rtrations from 0.012 to 0.18 percent.
All st -'-s of the tick have been killed with concentrations as low as 0.03 percent
of the gfr-.r, a isomer. However, even at 0.18 percent the residual action
has -.e' been marked. At Ke-rvule, Tex., a 0.06-percent spray protected
animals for F-': ut 4 -'.ys, but after 1 we-k some ticks were beginning to
E'l,-rge ConcE itr..-(ons higher than 0.06 percent did not seem to pro-
lon the protecting to any rr.-.rked c degree. In comparative tests DDT
faie o i I a --ed ti-k- at a concentration as high as 1.5 percent.
HoE er, DT rcvi better -'-tection against rerLSe station than did
bez ,Ox. lri( TL- c.'tron obtai ed with sprays containing 0.5
.'.t O. '- 7 .:,T ,oc.- t.: r o 2 w ek t;.s .c,
0 '' pp of1 W ~ 4-r 2 -eeks coriiparable with that obtained
.- 1 --.." wit' ~ ..rcent co centration of the garrm.R isomer. The
0.>5- Y..'rcent '.!DT sp:'y ,ded about 5 percent protection for 2 weeks.

W i.'-,t r .ck

ipr-ays containing benzene hexachloride have been tested on cattle and
sprays or wishes onr hor3-es for control of the winter tick (Dermacentor
albipictus (Pack.)) in the vicinity of Kerrville. Good control of all stages
resulted w-it* a concentr .tion as low as 0.012 percentof the gamma isomer
when the ordinary technical material was en. ,1)yed. Concentrations of
0.03 and 0.06 percent protected animals against reinfestation for about 2
weeks. DDT emulsions and wettable powders failed to kill all engorged
ticks at concentrations up to 2.5 percent, but P.5- to 0.75-percent concen-
trations pro, ided protection for about 4 weeks.

Ear Tick

In labo-ator- and field tests benzene hexachloride was effective against
the ear tick (Otobius reiv, ini (Duges)) when applied as a spray. However,
little is known about the most practical concentrations required to control
this species or about the duration of effectiveness when wettable-powder
or emulsion sprays, are employed. The Bureau of Animal Industry
(F-armers' :i- elir, No. 980) has shown that benzene hexachloride in a
pine oil- :-.'e.Ie solut.o will effectively control this parasite.






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Other Ticks

Tests against the Gulf Coast tick (Amblyomma maculatum Koch)
indicate that benzene hexachloride is about as effective against this
species as against the lone star tick. Various investigators have also
shown that this insecticide is highly effective in killing all stages of the
cattle fever tick (Boophilus annulatus var. microplus (Can.)).

Flies

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 long-lasting control. Sprays applied on cattle for the
control of horn flies at gamma-isomer concentrations of 0.025 to 0.05
percent generally become ineffective in 3 to 4 days as compared with 3 to
4 weeks for 0.5-percent DDT. In laboratory tests conducted at Orlando,
Fla., deposits of benzene hexachloride containing approximately 20 to 40 mg.
of the gamma isomer per square foot (200 to 400 mg. of technical product) gave
nearly complete control of house flies exposedfor 2 hours as long as 9 weeks
after treatment, whereas DDT applied at 50 to 400 mg. per square foot
was completely effective at the end of 36 weeks. Recent tests with DDT-
resistant house flies indicate that such flies show only slight resistance
to benzene hexachloride. The Agricultural Experiment Station, at Riverside,
Calif., has reported favorable results with the insecticide in California.
Preliminary field tests conducted by the Bureau in Florida have also
shown favorable results with this insecticide.
Benzene hexachloride has been reported to provide some control of
horse flies and deer flies. In tests conducted in Texas against Tabanus
abactor Philip, all flies feeding on treated cattle for 1 to 2 days after
being sprayed were killed. In Georgia some success against tabanids was
indicated with mixtures of benzene hexachloride and methoxychlor. 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 necessary to determine
the value of benzene hexachloride in practical control 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 control
measure.






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Common Cattle Grub

Benzene hexachloride in certain tests has given some kill of the
common cattle grub (Hypoderma lineatum (De Vill.)). Its performance
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

Chlordane has been employed extensively for the control of certain
household pests, and is also being used against various livestock pests.
Rather extensive tests have been conducted with this insecticide against
most of the major pests of livestock.
Chlordane is a viscous liquid, readily soluble in a number of solvents,
including petroleum oils. Both wettable-powder preparations and
emulsions have been used. Under some conditions this material exhibits
a fumigating property in addition to its usual contact action.

Cattle Lice

Chlordane, in both wettable-powder (50 percent) and emulsion-con-
centrate (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 treat-
ment. The tail louse also appeared to be equally as susceptible to
chlordane as to DDT. The concentration needed for practical or complete
control has not been determined, but a 1-percent chlordane spray gave
complete control in one test.

Goat Lice

Chlordane and DDT were found to be equally effective against red and
yellow goat lice in tests conducted in Texas. A single treatment in a
0.2-percent chlordane 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.

Hog Louse

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






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concentration. DDT in the same test gave good initial control, but a few
lice were found after 3 weeks.

Sheep Tick

Dips containing 0.05, 0.2, and 0.5 percent of chlordane gave complete
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 at a gamma-isomer concentration of 0.025
percent.

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 concentra-
tions gave complete or almost complete control of the flat stages, and
the 0.75- and 1.5-percent concentrations gave nearly complete kill of all
stages. DDT failed to kill all the engorged forms at 1.5-percent con-
centration. 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 hexachloride for
tick control.)

Winter Tick

Chlordane is distinctly superior to DDT against the winter tick on
cattle and horses. Complete or nearly complete control of all stages has
been obtained with 0.75-percent sprays, whereas DDT at 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.

Flies

Chlordane has been tested on animals exposed to horn flies in cages,
and has also been used 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 concentrations of 0.25 and 0.5 percent, applied at the
rate of approximately 2 quarts per mature animal, gave good control of






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horn flies and protected the animal for about 3 and 4 weeks, respectively.
There was no clear-cut difference in effectiveness between DDT and
chlordane, although chlordane appeared to be slightly inferior.
Chlordane is more toxic than DDT to house flies. Its residual action
is l<,ng lasting but not equal to that of DDT. In laboratory tests at Orlando,
Fla., surface treatments of chlordane at the rate of 200 mg. 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
considerable promise for chlordane as a substitute for DDT in such
situations.
Chlordane applied as a 2-percent emulsion did not protect cattle
from attack by tabanids 'Tabanus abactor) but caused 100 percent kill
of feeding flies on the first day and 60 percent on the second day after
treatment.

Screw-Worm and Fleece Worms

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
it,- ,ntial use for controlling these insects.

Common Cattle Grub

S.en emulsion and wettable-powder formulations containing up to 1.5
percent ,'A ,_, t _n,- w, i --. applied to cattle, either as a wash or with a
S'.h-power sprayer, tl-ie mortality of cattle grubs was less than 20 percent.
Dusts containing up to 5 percent of chlordane also proved inc ifective.

Toxaphene

Toxaphene (formerly called chlorinated camphene) 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 ils. 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 con-
centrates from 25 to 65 percent with xylene or kerosene as the solvent.

Cattle Lice

When tested as sprays at concentrations of 0.25 and 0.5 percent,
toxaphene gave results that were comparable with those obtained with





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DDT, benzene hexachloride, and chlordane against both short- and long-
nosed cattle lice and the tail louse.

Goat Lice

Toxaphene appeared to be at least equal, and perhaps superior, to
DDT, chlordane, and benzene hexachloride against red and yellow goat
lice. In limited tests apparently complete control was obtained with dips
containing 0.05 percent or a slightly lower concentration of the insecticide.
Dips at 0.2-percent concentration have kept goats free of lice for at least
4 months.

Hog Louse

Only one test, involving a few animals, has been run with toxaphene
against the hog louse. A wettable-powder spray at 0.2-percent concentra-
tion gave. apparently complete control of the lice, being superior to DDT
and comparable with chlordane.

Sheep Tick

Against the sheep tick toxaphene was superior to DDT when used as
either a dip or a spray, but it was less effective than benzene hexachloride
or chlordane. In a few tests complete control was obtained with dips
containing 0.05, 0.2, and 0.5 percent of toxaphene. However, its action
appeared to be slower than that of the other insecticides.

Lone Star Tick

Toxaphene 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 DDT and chlordane. Sprays at 0.75-percent
concentration gave good control of all stages and protection against re-
infestation for 2 weeks.

Winter Tick

Toxaphene was superior to DDT and comparable with chlordane against
the winter tick on cattle and horses, when employed either as a spray or
as a dust. Good control of all stages and protection against reinfestation
for about 2 months were obtained with sprays containing 0.75 percent.
A 0.5-percent spray failed to control all the engorged forms, but prevented
further reinfestation for 6 to 8 weeks.





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Gulf Coast Tick

Rather extensive tests indicate that 7 action c to.....h.,e .-'eTainst
G", Coast tick is sim .i to '! .* ,.- t the l..- star tick. Go,
c. .trol of all sta -s resul- i. wh- cattle -'-re wi' or rrjy.rd with
0.5to 0.75 per( I of the irns. .,U''-: i-tection :_.,ainst reinfestatio2
was obtained for 2 to 3 v. .k--. In t,-,se tests DDT *'a., less effective in
killing the _.*igorged ticks, b'u-t the dt -ree of protection ai'torded after
treatment was similar to thrt obtained with toxaphrne.

Cattle Fever Tick

Extensive tests conducted in South America / have shown that sprays
containing 0.5 percent of toxaphene are highly effective against all stages
of the cattle fever tick present on animals. Complete protection was
obtained for 3 weeks and good control for 4 weeks. Protection after 3
weeks was comparable with that obtained 11 to 13 days after treatment
with a spray containing 0.5 percent of DDT plus sufficient benzene hexa-
chloride to give 0.025 percent of the gamma isomer.

Ear Tick

Toxaphene was superior to DDT and comparable with chlordane and
benzene hexachloride for controlling the ear tick. However, further
studies are needed to determine its value for this purpose.

Flies

Toxaphene at 0.5-percent concentration has given results similar to
DDT 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.
Toxaphene is less effective than DDT against house flies, from the
standpoint of both initial killing action and residual action. Little in-
formation is available on the relative efficiency of the two materials
against stable flies (Stomoxys calcitrans (L.)). Toxaphene as a 2-percent
spi ay did rnt protect animals from attack by tabanids or stable flies.


Jj The.e tests were c,. ,.ducted by E W. Laake, Bureau of Entomology
and Plant Quarantin'- while on leave as A consultant for the American
International Association for Economic and Social 1 -?velopment.





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Screw-Worm and Fleece Worms

Toxaphene is 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 its value for controlling either of these
parasites under practical conditions.

Common Cattle Grub

In small-scale tests toxaphene did not control larvae of the common
cattle grub.

Methoxychlor

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 or 25-percent emulsion
concentrates. In general the wettable-powder preparation seemed to be
somewhat more effective than the emulsions.

Cattle Lice

Sprays containing 0.5 percent of methoxychlor gave good control of
short-nosed and long-nosed cattle lice. It also showed promise com-
parable with that of DDT for controlling the tail louse.

Hog Louse

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.

Sheep Tick

In tests in Oregon methoxychlor controlled the sheep tick when used
as a wettable-powder dip containing 0.2 and 0.5 percent of the insecti-
cide. The insecticide appeared to be slightly less effective than DDT.

Ticks

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 or engorged winter ticks or lone star ticks on
cattle and horses, and animals became reinfested by the second week.





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In laboratory dippir.g te st' it was less effective than DDT against the
lone star tick and tl.r ear tick.

Flies

hiethoxychlor gave good conrol of the horn fly on cattle. In some tests
it gave resuls comparable with or superior to DDT. In others the dura-
tion of t- fectiv, iess ,,as less than that obtained with DDT. 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 other tests,
conducted in Missouri and Kansas in cooperation with the State experi-
ment stations and the National Livestock Loss Protection Board, longer
protection was obtained with methoxychlor. When treated animals were
exposed to flies in cages, this material was slightly inferior to DDT in
lasting effect.
Methoxychlor has shown considerable promise for the control of the
stable fly. In cage tests a wettable-powder spray containing 0.5 percent
of methoxychlor applied to cattle prevented feeding of stable flies for
several days and killed most of the flies that took blood during the first
week after treatment. DDT at the same concentration did not prevent
flies from feeding but killed flies that took blood during the same period
of time.
Under laboratory conditions methoxychlor is almost equally as long
lasting as DDT against both the house fly and the stable fly when applied
as a residual spray. Treated screen-wire cages exposed to sunshine and
weathering remained toxic to stable flies longer than similar cages
treated with DDT. Recent tests have shown that DDT-resistant house
flies are only partially resistant to methoxychlor. Field tests in Florida,
Texas, and Georgia have shown promise for methoxychlor as a residual
treatment for controlling house flies; however, the results have been
some what erratic.

TDE

TDE (also called DDD) is another crystalline substance closely re-
lated to DDT in chemical and physical properties. The types of formula-
tions used are also similar to those of DDT. Tests conducted with both
emulsion and wettable-powder formulations have thus far shown no
difference in effectiveness.

Cattle Lice

TDE was about equal to the other chlorinated insecticides in effective-
ness against short-nosed and long-nosed cattle lice. A 0.5-percent spray






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thoroughly applied gave good control of thesE insects. Preliimln.-ry
tests have indicated that TDE is also comparable with DDT for the
control of the tail louse.

Hc-. Louse

In preliminary tests run on a few hogs TDE was eq,__2 to DDT in
initial kill of the hog louse. Neither material ..ve comnpl-,te J,.r
at 0.2-percent concentration

Sheep Tick

TDF -?.pve good control of sheep ticks when en.l.:o -r. as a j-, at con-
cc-ntrations of 0.2 and 0.5 percent. It was about equal to me".. '-.- '. r
but less effective ti-an the ,i.ter chlorinated hydi oar.. .- *t'ci '.s.

Ticks

In labor ,tory dipping n .ts agoirYst the lon, 'n i r tik .V :,_r T '-,t so
&r- ctiv,- '--. chl rrdane, benr-,.- hexachlo.idi, toaphe-6 o1r .'DT.
In a !i.-.lted number ct L sts agains_.t the printer ti, TDE was -..-,
irately c-.ual to Dr biut inferior to toxap! ene and chlT -'i.,e. Spra,-:
co.:.-ini.: 0.5 to 0.75 percent of TDE did *"ot kill ern org_,:-,*, tiik.s but
prevented reinfestations for about 1 month.

Flies

TDE g-Are satisfactory cc-tro! of horn flies on beef and dairy animals.
I.- general at 0.5-per.'e-i cnn,"- -*'on (in a wettable powder) this
atetial w-.: about equal 1 met c.-ychlor and slightly less effective
'n DDT nd toxaphuie.
In 'L"-.-rrPorv t-:--ts TDE ws less effective th-.-.. DITr' ag-inst the hc-,osf.
.o ;--- :,,ary tests in th.- laboratory an:1 on caged trr.-ated cattle
-... T ._P w'.s '.,r .rable w...ita-. rPDT in effect jit.* a,- ":.- t
, .... Si& r-li 7

nr i :. y- Butc xid.:

.. .. ,".v -:-. .,:., s., .- is so' *w -t .I.Qr e -: i, 'd.., b'_' it is '-u' iief
,rtst f M:? :,- nbL_.,ation "*.ith .v:; ,th-4.'.m i-.ich i w .ir-ly ,-. in
. te r; f. TI,- insecticidal action of pyrethrum i. pid and it is
e* fc _St .:,n us irr -v-.looded ai-.imals, but it is costly ant is unstable.
": .e adioT%- of pip. .yl butcxide to pyrethrum at a ratio --f 10 to 1
-creases the irize'ticidal action and the duration of its effectiveness.





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Additional tests are needed, however, with different formulations against
;various insects and under varying conditions before precise information
can be given regarding the performance of such insecticides as residual
treatments.
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 treated animals after 2
weeks.
Sprays containing 0.1 percent of pyrethrins and 1 percent of piperonyl
butoxide protected animals against stable flies for 2 to 6 days. Some
protection against tabanids was also indicated, although results reported
by several investigators vary considerably.

TOXICOLOGICAL INVESTIGATIONS

The toxicological effects of the various insecticides on man and
animals are of primary consideration in connection with their use for
the control of livestock pests. Some of the insecticides or insecticide
compositions might prove hazardous to persons handling them, and if
employed in excessive amounts or if improperly formulated and mixed
there is a definite danger that some of them will produce harmful effects
or death when applied to livestock. However, other, more complex
toxicological problems arise in connection with their use. It is known
that when some of the insecticides are applied to livestock small amounts
appear in the milk. It is known also that heavy applications of the insecti-
cides will result in storage of chemicals in the fatty tissues. Little
information is available at this time on the quantity that might be stored
when the insecticides are applied in amounts and at the frequency needed
to control the insects, although such studies are now under way.
It has recently been found that the treatment of dairy barns with DDT
and TDE for house fly control resulted in the appearance of appreciable
amounts of the insecticide in milk of the dairy animals.
The occurrence of some of the chemicals in the milk following its
application to dairy cattle and its possible occurrence in milk after barns
have been sprayed is a matter of considerable concern even though the
quantity may be small. Milk serves as the major portion of the diet of
infants and children. Studies conducted by the Food and Drug Admini-
stration during the last several years have led to the conclusion by that
agency that even small amounts of DDT could in time prove hazardous
to man when consumed in the diet. A statement recently issued is quoted
in part as follows: "The Food and Drug Administration has the duty of
protecting the inter-State food supply from adulteration. DDT is a poison
and its use under conditions which would contaminate milk--a food so
universally used by infants and children--would be contrary to the Food,
Drug and Cosmetic Act."





-15-


In answer to a recent inquiry as to whether methoxychlor might be
a suitable substitute, a representative of the Food and Drug Administra-
tion stated that methoxychlor "would probably be unobjectionable from
the health viewpoint but that its effectiveness was a question for
entomologists to answer."
In view of the new information and interpretations of available data
relating to the toxicology of the insecticides, changes in recommenda-
tions relating to the use of some of them are being made by this Bureau.
These changes will be discussed in this report after the information on
the various new insecticides now available is reviewed.
The Food and Drug Administration has investigated the toxicology of
the various new insecticides to laboratory animals. The information
given here on the toxicity to small laboratory animals is taken for the
most part from recent papers by A. J. Lehman,2/ pharmacologist of
that Administration. The data represent general averages for several
kinds of laboratory animals, usually employing chemicals of high purity,
rather than the ordinary technical grades. Since most of the studies are
incomplete and many of the formulations differ from those commonly
employed in treating livestock, the information indicates trends or
approximate toxicity only. The Bureau of Entomology and Plant Quaran-
tine, in cooperation with the Bureau of Animal Industry and the Texas
Agricultural Experiment Station, conducted most of the toxicological
studies on livestock that are reviewed in this report. Most of these
studies were carried out at the Kerrville, Tex., laboratory and at the
Agricultural Research Center at Beltsville, Md., with funds provided
under the Research and Marketing Act.
The toxicological investigations on livestock have for the most part
been along the following lines: (1) Studies to determine the effects on
livestock of various insecticidal chemicals and formulations of them in
insecticides when applied externally; (2) studies to determine the amount
of insecticidal chemical secreted in milk when insecticides are applied
to dairy animals in amounts and frequency necessary to control horn
flies and other parasites; and (3) a determination of the amr.,'_,t of milk
contamination resulting from the application of residual insecticides in
dairy barns. Some studies and observations have also been conducted
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 animJ tissues resulting from
external treatments are under way, but insufficient data are available
to include them in this discussion. Limited chron.'c-toxicity studies


2/ Lehman, A. J. The toxicology of the new agricultural chemicals.
Bul. Assoc. Food and Drug Officials 12(3): 82-89, 1948. Another paper
under this title was presented at the 42nd annual convention of the
National Canners Association, Atlantic City, N. J., Jan. 17, 1949.






- 16-


involving repeated treatments of livestock with the various -insecticides
over a pe. : L- of months are '.,,d.-r way, but no significant dai'a are avail-
able at prese,,t.

Dr f

The mean lethal oral dose :f "DT to iabo:-:iory -'-.;',As a cr.'es
a out 250 "-i-. pT r k 2 grari cof bc ..,.: F"om .I',, stand point of
r.1i! 01- t C:A "ciV o, Food aiic1 Drug .'.r-i;. ration rep -,-rts evidence of
liver :.r-.e in certain laboratory animals that are orni*.'i..,,usly fed a
diet co, .... 5 p.pm ," DL,_.
W1; 11 l, -.:c.-.rr .Ty,. UDT in d-rv form shows no "i s
toxic effp.: on laboratory animals. in solutiinr, ai-. :. c., tolera', a
single applicai.- to '-he skin of up to 3 grams per kilhgramrn However,
rz-peated -...ure to DDT in solution incr-e.a.' the hazard as much as
20 times that c si -'ie ex .os.-e.
On cattle as -anry as 10 a: Ilic.- t"ons of a 2-percent DOT ;v.'ttable-
pG,'..>r spray at 2-Aeek3 in.;exvals have prodi,'ed !.c visible Foss oxric
effects. Single treatments n"..th wettable-powder ri.rays cont-"ing as
-ac as 8 o., _e t f .DD can be -.lerated wift.oui. ap:.2,ent harm to
-l. No :e.r:. r effects have h not-. with xy"e,'c-i --ije emulsions
.:-i '... D'3 at the sa..e concznt,-ations. However, it is known "that
certain I'c-s cf scl i.e...S. nave produced har-.hj i ffec:t-.- wh-?n applied in
e.--usi:.:. nfori, :-r the :resence of DDT mn.ght i;-irrease the c;xicity of
s, fo~i~r= nations :'" ,e>. stik.n of storage in arimirn tissues of DDT
:.t ha? lied to livestock in ":,,.-ounts u--ed for insect control is
now u der P
.w n .v .:.!' ; :..d;iv ,.of an, sample s f t .'.en from dairy
., ot.'r-l.In '947 ,,e:.ysamples -.f milk
cat*V. treated .'.-'th D,.,T for ", ontrK In 1947 .ve&.ly samples .f milk
xwe-e analy?-,l frorn tVwo hras near rvill;, Tex., which had been treated
vith 0.5w-.p'. DD T wet .i'3 e-powd"- r spray foxr c( ntrolling horn flies.
St"a! .i w- . about 1 month apart. All samples of milk
W ...r se. t. .. -D:... .. ra;-ged from 0.1 to 2 .p.p.m., and
ave;., About 0.6 t,.: 0.7 .p i, .
In 1 s:. sirr ar st --ir- were conducted on four herds in the Kerrville
,;xa. r;--: :' ls were treated as ofti-. as necessary to control horn
flies, with 1 to 2 quart_ of a 0.5-percent DDT spray made from DDT-
xylene-T.riton .iicentrate. 'The amount of DDT in the milk was some-
what less .-..n in 1947, averaging about 0.25 p.p.m. The barns were
also tr',..ed with the same emulsion at the concentration and frequency
s '-- sa r y f o r eo n 4 r q '
e-L-sary for contr'.Ili..' house flies. It was shown that the amount of
DDT appearis7 in the milk after barn spraying increased in some cases
for a day or two but it quickly dropped to that present after DDT had
been applied to the cattle. However, the barn sprayings did not in all
cases cause an appreciable increase in the DDT content of the milk.
DDT in the milk attributed to barn sprayings occurred in four of eight






-17-


sprayings. The amount attributed to barni treatment in on.- case was
approximately 1.23 p.p.m. on the day after the spraying, but on the
second day it dropped to about 0.25 p.p.m. The average for the se:,3on
which could be attributed to barn sprayings was calculated to be ,'.',ut
0.1 p.p.m. of DDT in the milk.
In another experiment, several indi-idual Jairy cows under controlled
conditions were treated four times at 1-month intervals with a 0.5-percent
DDT wettable-powder spray. The DDT in the milk averaged about 1 p.p.m.
during the test period.

Benzene Hexachloride

The different isomers of benzene hexachloride vary in :'.-ir Ir -Icity
to hhcr ani.mals. For the gamma i--omer the mean lethal dose to
labor,':). -,, iimrnals,when administered by --.th, is approximately
125 rngi. -r kilogram -'f body- '.',eight. In .il solution it is readily abso'
L,:.;u._ the skin; when it is adrn ii'isterL-. in "n wa., '} m i
to .'oratory d.imals rs .-ges fr rr. 20 to 50 rmg. per .-.:.o_. ... .,.d
Tr.d D1-'1:.' Adninristratiion has informally advise. dr the B'- a t "
-:j-. a isomer ocf benrzre. exachloride appears 1 be somewhat less
toxic f'-'om a .ihronic standpoint than DDIT. Furthr.rn-more, lb.. s less
tenjnu-iic'y for storage of the chemical in animal fat and it is no ..'ckly
eliminated. However, that agency considers the !-,-ta isomer of b< :.ene
hexachloride to be especially hazardous from !he standpoint of chronic
toxicity: therefore, this isomer should be eliminated from benz ene I -xa-
chloride insecticides. Although the alpha and delta isomers are of a
similar ordcr of chronic toxicity as the gamma, they should also be
eliminated insofar as possible, since they increase the toxicity hazard
and add little to the effectiveness of benzene hexachloride insecticides.
At Kerrville high concentrations of benzene hexachloride and frequent
treatments were tested to gain information on the upper limits of toxicity.
When mature or nearly 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 (0.15 to 0.18 of gamma
isomer). 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 wettable-
powder spray containing 2 percent of benzene hexachloride (0.2 to 0.24
percent of gamma isomer) showed no apparent harmful effects. Ho'.:ev.r,
when a wettable powder containing 50 percent of gamrma benzene \ -
chloride was used, all 3 cattle treated once with a spray vc'-.:nin,': 1.5
percent of the gamma isomer were killed, but 1 out of 3 spray *id with





-18-


0.75-percent gamma died and another was seriously affected but re-
covered. 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 same gamma content were apparently less toxic but toxic
symptoms were evident in two of nine calves treated and one calf died.
Tests on calves were made with three samples of benzene hexachloride
of different gamma content--namely, 12, 36, and 95 percent. When
diluted to the same gamma content, all three sprays were equally toxic.
Few reports have been received of death or injury among calves or
cattle following treatment with benzene hexachloride in actual use for
pest control. However, these available toxicity data suggest that the
margin of safety for benzene hexachloride applied to young calves is
extremely narrow. Suckling pigs and lambs appear to be much more
resistort than calves.
To deteririne whether the use of benzene hexachloride gave off-flavor
or odor to meats of treated animals, tests were conducted with several
kinds of animals. One pig received two thorough treatments 9 days apart
with a spray containing 2.5 percent of technical benzene hexachloride
(0.3 percent of gamma isomer). The animal was killed 2 days after the
second treatment, and 10 families cooked and tasted the meat. None of
the families detected benzene hexachloride taste, but two of them detected
the odor while the meat was cooking. Another pig was sprayed twice 4
days apart with 1.5 percent of technical benzene hexachloride, and
slaughtered on the sixth day. None of the families eating the meat
reported benzene hexachloride odor or taste. In similar tests with a
goat, a sheep, and a yearling calf, one report of benzene hexachloride
flavor or odor from each animal was received. Another calf and a pig
treated eight times at 4-day intervals with a spray containing 1.5 percent
of technical benzene hexachloride (0.18 percent of gamma isomer) and
slaughtered 1 month after the last treatment showed no marked off-flavor
or odor, although some individuals gave positive reports. In tests with
six chickens exposed for one to several weeks to roosts heavily painted
with a slurry of technical (12 percent gamma) benzene hexachloride,
conflicting reports were received, but in one chicken marked benzene
hexachloride odor was detected.
In these tests the concentration of benzene hexachloride was in excess
of that needed for controlling the parasites. In a thorough test conducted
in cooperation with the Missouri Agricultural Experiment Station, no
off-flavor or odor was detected in meat from a cow dipped approximately
18 times over a period of 2 years in a wettable-powder dip containing
0.5 T" recent of technical '" he;.-- he,-chloride (0.05 .percent of gamma
ioer). Io report: o: off-f, v or o .r .. meat from livestock treated
with c1. chf cr r. .. t rcr', ,1 h1 '-'e *.-c; e to the
a o 4* ..









Chlordane


The acute toxicity of chlordane administered orall, to laboratory
animals is reported to be about half that of DDT. However, the toxic ,'
of a solution applied repeatedly to the skin is reported to be greater for
chlordane. From a chronic-toxicity standpoint this insecticid for the
present is considered by the Food and Drug f^hmir.i -ration to be in "
same category as DDT, or perhaps more toxic, when taken in the diet
of animals.
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, and the same numbers of animals were treated with a wettable-
powder preparation at the same strength. The test was r. iea'.ed with a
new lot of chlordane, but only five sheep and two pigs were treated w4ith
each preparation. In the first test none of the cattle or horses were
killed with either preparation, but the sheep and t .'-,.. of "... .ts re
killed by the emulsion and two sheep and t\,-,. goats bv I .- wettabl powder;
some of the animals died after the third treatment. Ir ,. second test
none of the animals were killed.
The Livestock Loss Prevention Boar.1 obt.'in,:I--' similar results in
that sheep were killed by the severe treat-. itrt, and or.. of two cattle
sprayed with the emulsion and one of two sprayed wit. ihe wettable-
powder suspension was killed.
In another test at Kerrville 3 of 10 cattle died after four thorough
treatments at 2-week intervals with a 2-percent wettable-powder pre-
paration. No explanation can be offered for the variable results.
Tests on a few young calves 2 to 6 weeks old indicate that chlordane
is about as toxic as toxaphene when single applications are made.
Suckling pigs and lambs are much more resistant than calves.
Weekly analyses of milk samples from two dairy herds treated four
times with 0.5-percent chlordane wettable-powder spray 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.

Toxaphe ,e

Toxaphene is reported to be about fc-,r times as toxic as DDT when
administered orally to various laboratory animals, tr ean lethal dose
being about 60 mg. per kilogram. Wlin 2pplie, i' '- skin, it is also
far more toxic than DDT. When tak-.n or:i"" in ti., diet, to: he is
considered by the Food and Drug Administration at ths ti t in the
same category as DDT, or possibly less toxic, f croi-toxicity
standpoint.





-20-


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 per-
cent of toxaphene, no adverse effects were noted on any of the animals.
The older domestic animals show no ill effects from single applications
of emulsion sprays containing 8 percent of toxaphene.
Young calves are more susceptible to this insecticide. After reports
were received that it caused death of some calves dipped in Texas, tests
were made on calves 1 to 2 months old. A single spraying with 1.5-
percent toxaphene emulsion (containing xylene or kerosene) or wettable-
powder suspension caused toxic symptoms in some of the treated calves,
and two treatments 4 days apart caused a few deaths. Single and repeated
treatments at 0.75-percent concentration had no adverse effect on 12
calves. Suckling pigs and lambs are much more resistant than calves.
Field observations indicate that deaths among cattle treated with
toxaphene were due in part, if not entirely, to the use of faulty formulations.
Milk samples from dairy herds treated four times at about monthly
intervals with wettable-powder sprays containing 0.5 percent of toxaphene
were analyzed for organic-chlorine content. Of 43 samples analyzed, 27
were negative. In the samples giving positive results, the amount 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 toxaphene.
Preliminary investigations on storage of toxaphene in fat of cattle
when the insecticide is applied repeatedly as a 0.5-percent emulsion spray
indicate that there is no marked tendency for accumulative buildup of
toxaphene in the fat.

Methoxychlor

Methoxychlor is the least toxic of the insecticidal chlorinated hydro-
carbons that have been investigated. The mean lethal dose to various
laboratory animals when administered orally is reported to be greater
than 6 grams per kilogram of body weight. The Food and Drug Admin-
istration has also found methoxychlor to be of low order of toxicity when
fed in the diet to laboratory animals. From results of tests of single or
repeated applications of methoxychlor in solution to the skin of laboratory
animals, this insecticide is the least toxic of the new insecticides,
including piperonyl butoxide. On the basis of tests on laboratory animals,
the average toxic dose is estimated to be about 2800 mg. per kilogram
for single exposure and 600 mg. per kilogram of body weight when applied
repeatedly.
At Kerrville no adverse effects were noted when sheep, cattle, hogs,
and horses were treated repeatedly with emulsion or wettable-powder
preparations containing up to 2 percent of methoxychlor. Single
applications of up to 8 percent of methoxychlor showed no adverse
effects on young calves.






-21 -


Milk samples collected at weekly intervals from two herds of dairy
cattle treated five and six times during the season with a wettable-powder
suspension containing 0.5 percent of methoxychlor were analyzed for
organic-chlorine content. Only 3 of 42 samples analyzed showed organic
chlorine (0.1 p.p.m.) present.

TDE

The mean lethal oral dose of TDE for several laboratory animals is
reported to be about 2.5 grams per kilogram of body weight. Although of
a low order of toxicity from an acute standpoint, the Food and Drug
Administration now considers its chronic toxicity to be in the same
category as DDT, or possibly less toxic.
At Kerrville sheep, goats, cattle, hogs, and horses showed no illl
effects when treated eight times at 4-day intervals with 1 .5-percent
TDE emulsion or wettable-powder preparations. Single applications of
as much as 8 percent of TDE have shown no adverse effects on young
calves.
In 1947 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. TDE in similar amounts was
found in the milk taken from several herds treated in a similar manner
during 1948. When TDE was applied to dairy barns, it appeared in the
milk in amounts at least equal to those obtained after barns had been
treated with DDT.

Piperonyl Butoxide

The mean lethal dose of piperonyl butoxide administered by mouth
to various laboratory animals is reported to be about 13 grams per
kilogram of body weight. On the basis of applications to the skin of
laboratory animals, the toxic dose averages about 1.8 grams per kilo-
gram for single exposures and 200 mg. per kilogram for repeated appli-
cations. Pyrethrum, with which this material is usually combined, alone
is also relatively nontoxic to warm-blooded animals, especially in the
small amounts generally applied. However, the medium lethal oral
single dose of pyrethrins is about 1.5 grams per kilogram.

SUGGESTIONS REGARDING
THE USE OF THE NEW INSECTICIDES

In view of the new developments, already discussed, which relate to
the toxicity of the various insecticides for the control of livestock pests,






-22-


separate considc r-cAtion r.ust be given t the materials u' 1 ul in control-
ling insects affecting (e,,ry cattle and lose that might be satisfactory
for controlling ,'ests attack.ng other classes of livestock. This publi-
cation is not intende.1 to ..ivE detailed directions for conir'U1ling var'.ous
livestock pests with in-. cticidk- J. Rather, its purpose is to suggest the
field of use for the new insecticl-s in the light of available information
or lack of information relative to their performance against the pests
involved and the pote-tial haza_ s connecc,,i with their use. Livestock
growers who contemplate employing any of the rraterials should consult
with ,- Triculturai workers in their own States .- are concerned with
].ivest. :';k-,,^-st oroblems.

Precautions

Proper care should always be exercised in storing, handling, mixing,
and applying the :nsecticides discussed in this circular.
Store insect cides where children, pets, and other animals cannot get
to them. Store those containing kerosene or xylene so that there will be
no fire haza. d. and do not mix or spray them in the presence of open
flame or sparks.
Persons handling, mixing, or applying insecticides should take proper
precautions to protect themselves against unnecessary exposure to skin
contact or breathing of spray mist. Operators who apply sprays con-
tinuously and repeatedly should wear respirators and clothing that protect
the body. Clothing should be changed frequently and if it becomes
saturated with spray should be laundered before it is worn again. Bathe
or wash parts of the body with which insecticides have come in contact.
Apply insecticides in a manner to avoid accidental contamination of
food and water for humans and animals.
Observe carefully the suggested concentrations and rates of appli-
cation. Mix the materials thoroughly and agitate them continuously in
the spray tank. If emulsion concentrates will not mix readily with water
and oily films accumulate, do not use the material.
Dispose of unused sprays in such a way as to avoid hazards.

IN SPRAYING DAIRY BARNS, TAKE SPECIAL PRECAUTIONS TO
AVOID CONTAMINATING MILK OR UTENSILS. COVER WATER CUPS
AND FEED TROUGHS, AND COVER OR REMOVE FEED WHILE SPRAYING.

DDT

The application of DDT to dairy animals results in its appearance in
milk in quantities judged by the Food and Drug Administration to be a
potential hazard to consumers. The Bureau therefore recommends that
this insecticide not be applied to animals producing milk for human
conzjun'iq.on. In the light of current information the Bureau also advises
that safe materials (to be discussed later) be used for insect control in





-23-


places where the milk might be contaminated, such as dairy barns,
milk rooms, rooms containing dairy feed, or in similar situations on
the farm. Nor should DDT be used for fly control in milk-processing plants.
Further investigations are under way to determine whether DDT care-
fully applied in dairy barns and other situations mentioned can be used
without causing significant contamination of the milk. The Bureau con-
siders that there is no basis at present for changing recommendations
regarding the use of DDT on other classes and kinds of livestock for
pest control. Likewise, DDT is still recommended as an aid in control-
ling flies in places other than those described above.

Benzene Hexachloride

If benzene hexachloride is to be used for controlling any livestock
pest, it is advised that only wettable-powder formulations be
used. Products of high gamma-isomer content are the least objection-
able from the standpoint of odor. Benzene hexachloride 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 gamma isomer concentration should be held down to 0.025 percent.
Benzene hexachloride is effective against house flies in situations
where DDT-resistant strains are prevalent. However, at present there
is some question regarding the possible tainting or contamination of
dairy products through its use. Pending further investigation, the Bureau
considers the use of benzene hexachloride inadvisable in dairy barns and
milk-processing plants.

Chlordane

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 sprays
applied repeatedly to livestock, additional tests with repeated treatments
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 DDT. However, the
Bureau advises that it not be used for fly control in dairy barns, milk-
processing plants, or similar situations.

Toxaphene

From the standpoints of economy and efficiency toxaphene is con-
sidered promising for the control of a number of livestock pests,
especially the cattle fever tick. However, some deaths of animals,
principally young calves, have occurred when this insecticide has been





-24-


er.1royed for the controll of i- e cil ., and ticks. The foi :'-,ulations er l'yf .1
in the.- :; .- .tlio:. wer-e not suitable for use, especially in dippLi. vats.
Si-, -e t. .*- centrations req'-,..'ed for cont-rlling certain liv,-stock .-c.ts
are --."t toxic level for ..Ju.ng animals, further iRv-i.-i-,'...ations sholud
be ,_L.'.'te.] ,I-t!. hinproved formrb!;,.is before sugge-tio )fiered
: -,: ii. -- its use against live'-ock 1pests.

Methoxychlor

.-}'t,..- :rb.-r is recomir _,-rded for controlling certain in- ipcts on dairy
T, :;-.-_l; a_:-;,r other livestock. Results to date indicate that for horn flies
and li ,& on cattle 'he insecticide compares rather favorably with LDT.
It : s..iugested that cattle be treated with a 0.5-percent spray, preferably
prepared from a wettable powder. For the control of horn flies about 2
*r- r .spray should be applied to a mature animal. If higher concen-
.rai, ,. c -ployed, the amount of spray should be reduced. For
ccntr 1 -tf li, the animals should be thoroughly saturated. Against horn
-"s 1- -it 3 to 3- weeks' protection maybe expected, as compared with
'4 4 v.",c'ks for DDT applied at the same rate.
Sr stable fly control on dairy cattle a tentative suggestion is to
,*'" 0.-perccrt spray, preferably a wettable-powder preparation,
o r twice a week to the leis, billy, and lower part of the sides of
e a-'mal. A light spraying on their backs at the same time will make
furtl r horn fl-. treatments unnecessary. Other cattle on the farm should
I!so be treated at regular intervals for horn fly control.
Methoxyr1'._.r has given pi or-iising but somewhat erratic results in
limit -1 te-ts against house flies and stable flies when employed as a
resiA -1 spray on buildings, fences, and similar surfaces. It is recom-
me' -d as a residual treatment in dairy barns and other places where
flies concentrate. A wettable-powder spray containing 2.5 percent of
-- ethoxychlor, applied &.t the rate of about 1 gallon for each 500 square
feet, is sugg-- :ted.

TDE
E should not be u:.-d on dairy animals. It may be used to control
-orn l':..s J. lice ,r, other livestock. For controlling horn flies a 0.5-
:. rt .centratior applied as a wettable-powder or emulsion spray
the rate c 2 quarts per animal is suggested. For louse control the
-mal shvId be thoroughly saturated with a spray of the same con-
central u,!.
New Pyrethrum Insecticides
-- ..r;e. new materials that increase the effectiveness of pyrethrum
-e available, but piperonyl butoxide is the only one that has been in-
ves'igated for controlling livestock pests. Because of the low toxicity
,f nip- :,i yl bu -:.'.ide-pyrethrum insecticides to animals, no hazards
should ordinarily be created by their use. (If oil solutions are employed,
e, essive amounts of oil may prove harmful to the animals.) This





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insecticide preparation should be considered for the control of lice, horn
flies, stable flies, and tabanids on dairy animals. Insufficient information
is available at this time to recommend the most effective and practical
concentrations and treatment schedules for controlling the different
pests. For louse control a thorough treatment with emulsions or
wettable-powder sprays containing 0.005 percent of pyrethrins and
0.05 percent of piperonyl butoxide is tentatively recommended. For
controlling horn flies and stable flies on dairy cattle a spray containing
0.05 percent of pyrethrins and 0.5 percent of piperonyl butoxide is sug-
gested as a tentative recommendation, treatments to be applied as often
as necessary. This spray can also be employed effectively as a space
spray for fly control in barns. However, insufficient information is
available at this time to suggest its use as a residual treatment.
Preliminary tests with emulsions in dairy barns have not shown much
promise when the insecticide is used as a residual spray.

Other Methods of Controlling Dairy Pests

Various oil-base or water-base sprays for application to dais" cattle
in small quantities as a light mist have been emriployed extensively in '
pest. These treatments, which contain pyrethrum, rot( rone, or organic
thiocyanate insecticides, provide temporary control of flies on the cattle
and have also been used as space sprays in barns and elsewhere. The
use of such materials and methods might again come into wider use
because of the restrictions placed on some of the newer insecticides
and because of the occurrence of strains of house flies that are resistant
to certain insecticidal residues. When these older sprays are used on
dairy cattle and in dairy barns, cattle other than milk animals, barns,
and other places where flies concentrate should be treated with
residual sprays of the types recommended in this circular in order to
reduce to a practical minimum the over-all fly population on the farm.
It is emphasized that rigid farm sanitation, especially manure
disposal, should be practiced to prevent fly breeding. The use of in-
secticides should not be relied on as the complete answer for insect
control. Well-screened buildings will also aid in excluding flies and
in preventing the contamination they may cause.






UNIVERSITY OF FLORIDA


3 1262 09239 2207








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