October 1945 STATE PLANT BOARD, E-673
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and plant Quarantine
SUMMARY OF DIr EXPERIMENTS ON INSECTS I/
THAT AFFECT MAN AND ANIMALS
By W. E. Dove,
Division of Insects Affecting Man and Animals
The development of DDT insecticides at Orlando, Fla., and their
use by the armed forces since 1943, as veil as tests made by other
workers of the Bureau of Entomology and Plant Quarantine and its
cooperators, have demonstrated that practical control of certain in-
sect pests of man and animals may be obtained with these insecti-
cides. The experimental work at Orlando was conducted under a
transfer of funds, recommended by the Committee on Medical Research,
from the Office of Scientific Research and Development, and the re-
sults were made available to the armed forces in various reports.
The present report is based on information gained from tests
made under conditions found in civilian life by workers in the
Division of Insects Affecting Man and Animals, in some oases with
the cooperation of other agencies. Many of these tests were sug-
gested by the findings of the Orlando group. It should be under-
stood that many of the tests were seasonal or regional in nature,
and that no recommendations for the practical use of DIT insecti-
cides against any of the insects are included in this report.
At Orlando it was found that a concentration oP 0.25 percent of
DDTf in diluents such as talc or pyrophyllite will give complete kill
of the body louse (Pediculus humanus corporis Deg.) when applied to
infested clothing. This concentration is too low, however, to give
lasting effects. When an individual's clothing is treated at the
rate of 1 ounce of a powder containing 5 percent of DDT, the powder
is effective for 10 to l14 days. When the same amount of a 10-percent
powder is applied, protection against reinfestation lasts for approx-
imately 21 days. Since the incubation period of louse eggs seldom
exceeds 21 days, a single application of the powder will eradicate
an infestation. WDT has no ovicidal properties; however, the newly
hatched lice are killed by the DDT residue.
I/ Includes other arthropods, such as mites and ticks.
Two methods of impregnating clothing have been developed. One
method consists in dipping garments in a volatile solvent containing
MIT. A dry-cleaning fluid such as Stoddard's solvent, or a light pe-
troleum fraction such as gasoline, was found to be suitable for this
purpose. Another method, designed especially for use in the field,
consists in dipping Zvrm'e.\ts in an emulsion of DDT. When either uie-
thod is employed, the clothing is wrung out and then dried. Both me-
thods are equally effective.
DDT was just as toxic to the head louse (Pediculus humans
humanus L.) as to the body louse. Because it was combed from the
hair, two applications of the 10-percent DIT powder, about 10 days
apart, were applied. The second application killed the newly hatched
lice before they were old enough to lay eggs. In practical tests on
a large scale a single treatment with a 10-percent powder gave com-
plete control in almost all instances.
The 10-percent DDT louse powder was used against the crab louse
(Phthirus pubis (L.)). Two applications made at intervals of 10 days
were completely effective in a large number of tests.
At Dallas, Tex., R. W. Wells and W. T. Hunt found that louse
powder containing 10 percent of DDT killed the motile stages of the
short-nosed cattle louse (Haematopinus eurysternus Nitz.), the long-
nosed bloodsucking louse (Linognathus vituli (L.)), and the cattle
biting-louse (Bovicola bovis (Nitz.)). A single treatment applied to
only a portion of the body was not sufficient for killing all lice on
the animal. Dipping of cattle was more effective than dusting or
spraying. The short-nosed louse succumbed to a dip containing 0.08
percent of DDT in a soluble-pine-oil emulsion, but not all the long-
nosed lice were killed by this concentration. A single treatment
with a dip containing 0.2 percent of DIT eliminated infestations of
both the long-nosed bloodsucking louse and the short-nosed cattle
At Menard, Tex., H. E. Parish and C. S. Rude found that a dip
application of 0.2 percent DDT in soluble-pine-oil emulsion, in which
*2 quarts of the liquid adhered to each animal, gave complete control
of all stages of the four species of lice that occur on goats in
that section. The dip left in the vat was effective against motile
stages of red and yellow biting lice (Trichodectes sp.) and the bl..e
bloodsucking lice (Linognathus sp.) on goats for more than 99 days
after it was first used. Following these preliminary tests herds
of goats were treated with the same formula, and it now aprlear,3 thla
lice may be eliminated on a ranch if every animal is dipped and no
infested ones are permitted on the premises.
Goats dipped in a soluble-pine-oil emulsion containing 0.I per-
cent of DIT were sheared 5 days later, and all motile lice were found
to be dead. At Beltsville, Md., E. A. Back exposed the mohair clipped
from the animals to larvae of the carpet beetles Attagenus piceus
(Oliv.) and Anth~qus vorax (Waterh.). Approximately 3 months later
about eight-nints of the larvae on the treated material had died and
the others appeared sluggish and starved. Larvae kept on untreattl
mohair were alive and appeared healthy. The results of this e-d
similar tests suggest that the 0.1 percent DIT dip may impart to mo-
hair a good resistance against hungry larvae for a storage period of
3 months or longer.
In Georgia and Florida W. G. Bruce and A. L. Smith found that a
soluble-pine-oil emulsion containing 0.2 Ipercent of DT was effective
in killing motile stages of a hog louse, Haematopinus adventcitus
Newm. Spray applications were effective during the first week, but
not for 13 days after treatment.
Owing to the hogs' habit of bedding together, the treated hogs
rapidly reduced the infestation among all the hogs present. Two
treatments with 0.2 percent of WDT emulsion eliminated all the lice.
At Menard, Tex., H. E. Parish found that the dusting of individu-
al hens with a shaker can containing 5 percent of DOT in pyrophyllite
freed them of lice. Whether the material can be applied safely in a
dust, spray, or aerosol to poultry in houses is not known. Its tox--
icity to fowls must be determined before large-scale tests are under-
Tests made with liquefied-gas aerosols against Anor:'
quadrimaculatus Say show that pyrethrum is mcre zfi'f&.tl- 71i1a Dll', in
both kaok-doii and kill. DOT, however, causes a high 1ll of mosqui-
toes when used at concentrations effective against flies, and its use
in combination with pyrethrum allows about a 25-percent reduction in
the amount of pyrethrm without loss in killing power. On the basis
of these tests the following formula has been used (figures in per-
cent): Pyrethrins 0.4I, DT 3, cyclohexanone 5, motor oil 5, and
dichlorodifluoromethane 86.6. The formula is about equally effective
against flies and mosquitoes.
A D1T-pyretbru spray can be finely dispersed mechanically and
is equally as effective as the liquefied-gas aerosols. An effective
concentrated-spray formulation is WDT 20, pyrethrins 3, cyclohexanone
20, motor oil 5, and kerosene 52 percent.
J. B. Gahan applied DDT sprays that left a residue on the inside
walls and ceilings of residences, barns, and poultry houses in two
9-square-mile areas near Stuttgart, Ark. In one area an average dos-
age of 56 mg. of DDT per square foot reduced the number of A.
quadrimaculatus 91 percent in 3 1/2 to 4 1/2 months. In the other
area an average rate of 208 mg. of DDT per square foot reduced such
mosquitoes 99 percent during the same period.
Tests with DIDT in the laboratory at Orlando, Fla., showed that
DDT was effective but less toxic to larvae of Culex quinquefasciatus
Say and Aedes aegypti (L.) than to comparable larvae of Anopheles
quadrimaculatus. In field tests in Florida dusts applied at the rate
of 0.1 and 0.05 pound of DDT in talc per acre gave complete or near
cc'mplete control of A. quadrinaculatus and A. crucians Wied. Dosages
of I to 2 pounds of DDT per acre, in areas having a uniform growth of
vegetation, prevented all but negligible larval development for 4 to
8 weeks. On account of the shifting of surface films by winds, a
minimum killing dose of 0.1 pound of DDT per acre appeared preferable
to the larger dosages for routine applications.
Oil solutions containing 5 percent of DIDT (weight per volume),
applied at the same rates as the dusts, were also effective for the
same species provided adequate coverage of the breeding areas was ob-
tained. Finely atomized sprays produced by paint-type spray equip-
nfnt, or from airplanes using equipment developed by C. N. Husman and
0, M, Lo(nocy at Orlando, were satisfactory for this purpose. When
Tplez aa a fine spray to the breeding areas, an emulsion containing
.1 201 1 riton X-iOC (an ,ar-alkyl poljether alcohol) 20, and xylene 60
-:',-;-it by weight, ad used at the rate of 0.1 pound of DDT per acre,
a lcqjl as effective as the same amount of DDT applied in oils.
In stalt'.l1zed :J.:.-Is here emulsions were mixed with the water at the
rItt :of 1 oart ..f rDT to I million parts of water, the breeding of
Anopheles mtosqui:Aves was prevented for 4 weeks or longer. When emal-
Sll.ors were applied in the same manner against culicine mosquitoes,
somewhat higher dosages were found necessary for Aedes and Culex
species than for Anopheles quadrimaculatus.
In the Upper Peninsula of Michigan, Ray Hutson reports that golf
players were protected from the black fly Simulium venustum Say
through the application of dusts containing 1 percent of DDT. The ma
terlal was applied with a hand dust gun to golf greens and tees at
the rate of about 15 pounds per acre. Bushes and shrubs were also
dusted liberally. The premises were kept practically free of flies
for approximately a week.
In preliminary tests in Oregon by C. M. Gjullin and D. Mote, dusts
and sprays containing DDT were unsatisfactory when used on wet soil
that contained larvae and pupae of deer flies (Chrysops spp.). The
adult flies emerged from the puparia on the top layer of mud, and thus
there was no opportunity for them to come into contact with .the in-
secticidal treatment of the soil.
Applications of concentrated emulsions and oils containing DDT to
the ears of cattle did not prevent engorgement-of blood by the flies
on the treated ears. The flies lived about 12 hours after engorgement.
In Wisconsin L. F. Warrick killed adult filter flies (Psychodidae)
with a residual spray (see Houseflies, p. 6 ) containing 2.75 ounces
of DIT in a gallon of kerosene, applied at the rate of 1.1 gallons per
1,000 square feet on the side walls of a sewage-filtration plant. As
the flies emerged from the scum on the surface of the water, they
rested on the treated walls and were killed. The habit of resting on
walls near their breeding and feeding places makes filter flies vul-
nerable to residual treatments of DM sprays.
Two days after the sludge beds of a sewage disposal plant had
been sprayed with 7 ounces of DDT2 in 50 gallons of kerosene, many dead
maggots could be seen in the cracks in the beds, but smaller numbers
were also found in the check beds where only kerosene had been used.
Five days after treatment the maggots could be found only in the lower
1/2 to 1 inch of sludge, in the DDT-treated area. In the check area
numerous maggots were working throughout the entire depth of sludge.
Twelve days after treatment no fly larvae could be found in the DMOT-
treated area. Few puparla were found, and they were present only near
the bottom of the sludge. In the check area, treated with kerosene
only, many puparia and active larvae were found and many flies had
emerged. The operator of the plant reported that the filter fly nui-
sance in his house and in the laboratory had been greatly relieved.
At Dallas, Tex., E. W. Laake reported 37 tests in which DDT
sprays made of emulsions or water-dispersible powders micronizedd ma-
terials that are easily dissolved in a suitable wetting agent) had
been applied to herds of dairy and beef cattle for the control of horn
flies (Siphona irritans (L.)). With a dosage of DT ranging from
0.67 to 1.4 grams per animal satisfactory control was obtained for 5
to 7 days. When three-fourths as much DDI was used the control was
of shorter duration, and when one-half as much DDT was used the re-
sults were unsatisfactory. Sprays containing emulsions in xylene or
in pine oil, applied at the rate of 4 or 5 grams of DIDT per animal,
gave excellent control for 14 to 18 days.
In Kansas, Texas, and Florida a 2.5-percent DIDT spray, made of
water-dispersible 50-percent DDT, was effectively applied to range and
dairy animals with power sprayers. One application to the backs and
bellies of the animals in chutes or corrals remained almost completely
effective for 10 to 15 days and a second application for 2 to 3 weeks.
In general the tests indicated that the period of protection depends
upon the quantity of DDT applied to the animal rather than upon the
volume of the spray or the kind of equipment used. With the methods
and materials used, satisfactory control for 10 to 15 days or more
was not obtained with less than 4 to 5 grams of DDT per animal.
E. W. Laake also reported that a herd of 250 purebred Herefords
were dipped in a xylene-soluble pine oil emulsion containing 0,.12 per-
cent of DDT. The herd averaged 4,000 flies per animal, but 2 hours
after dipping, and for 48 hours, the herd was entirely free of horn
flies. Observations on the 4th, 6th, 9th, llth, and 14th days after
dipping showed an average infestation per animal of 1.5, 3.8, 3.4,
5.9 (all afternoon observations), and 0.1 (morning observation) flies,
respectively. During this period (2 weeks) no reduction of the horn
fly infestation on check herds in the neighborhood was observed.
Another treatment was made with the same dip 14 days after the first
dipping. The two treatments gave almost complete control for at least
2 months, whereas untreated animals on neighboring ranches carried
from 50 to 1,000 flies during this period.
In Florida W. G. Bruce reported that effective control of horn
flies was obtained for more than 2 weeks with dips containing 0.2 per-
cent of DDO, as well as with sprays containing 2 percent of MmT, an
emulsion being used in both cases.
DDT was used effectively in sprays for treating favorable rest-
ing places of houseflies (Nisca domestic L.). When the sprayed sur-
faces became dry, the toxic DDT deposits that remained continued to
kill flies and other insects that alighted or walked upon them. These
deposits were effective for several weeks or month, depending upon
the kind of spray used and the length of time the sprayed surface was
exposed to direct sunlight or water. Because this method of applying
sprays differs from the direct applications of sprays against insects,
the term "residual spray" is employed to differentiate it from a
"space spray," the kind of spray ordinarily applied in the air as a
fog or mist. The DDT residual sprays found most practical to date
are suspensions of 2,5 percent of DDT from water-dispersible
powders, 5 percent in kerosene, or 5-percent emulsions prepared by
0iluting concentrates containing 25 percent of =DT, 65 percent of
Lylene, and 10 percent of Triton X-100.
,- ,rene spray, -- percent of DDT in kerosene (7 oz. in 1
l.) has been used effectively orderr a wide vax.ety of conditions
,uring the past 2 years. It has been esrayeed on favorable resting
p".-.ce3 for 'I`les in dairy barns at Beltsville, MdI, at several looa-
-,'~. ..., .la in Sout T rkota, and in eastern Montana. It has
T -.=-,-, 'p *. i walls I'.-"'. 'H ro.TE and on wvll.e and screens of re-
.idencee 1r, several State,. A single treatment at the rate of 1 gal-
lon to 1,000 square feet of surface (about 200 mg. of DDT per square
foot) was effective throughout the season. Some treatments were 95
percent effective for 4 months and continued to kill houseflies for
10 months, "'here the breeding places were neglected, flies emerged
faster than they were killed in the treated rooms. This is attributed
to the fact that I to 4 hours is required for killing the flies. It
is therefore possible for the newly emerged flies to become annoying
in treated buildings. Such occurrences emphasize the need for con-
trolling the breeding places of houseflies.
Horse stalls in Indiana and Florida and dog kennels in Florida
sprayed with this solution gave a high degree of protection to man and
animals from annoyance by houseflies and also from bites of stable-
The use of residual sprays only about the entrances of kitcLhvns,
restaurants, creameries, hospitals, cheese factories, meat-packliri
establishments, and a camp for cherry pickers gave considerable con-
trol for more than 2 months.
When the DDT-kerosene spray was applied to 150 square feet of a
shaded corrugated-metal siding of a building between a milk house and
a cooling room, it killed flies throughout the season, but the effec-
tiveness decreased by the end of the seventh week.
In some instances the spraying of unpainted wood, concrete, brick,
and plaster surfaces with kerosene containing DID was not effective
in forming a residue for killing flies. It appeared that such walls
absorbed the DDT.
Emulsion sprays.--At Beltsville, Md., L. S. Henderson sprayed
concrete barns with 2 percent of DDT in xylene emulsion, at the rate
of 200 mg. of DDT per square foot. This treatment provided surfaces
which killed flies for 1 month. When similar barns were sprayed with
a 1-percent emulsion, at the rate of 125 mg. per square foot, the
treated surfaces killed flies for 2 weeks and then became less effi-
cient. In several practical tests sprays containing 5 percent DETP-
xylene emulsions were effective on metal walls and on old painted
surfaces, but there was some objection to the white deposits on dark-
Water-dispersible powder sprays.--The water-dispersible powders
recently developed by different manufacturers are considered suitable
for spraying porous walls and ceilings of barns, stalls, and poultry
houses. They leave white residues on the treated surfaces, but do not
appear objectionable on whitewashed or white-painted walls of out-
buildings.- In the tests conducted so far the water-dispersible sprays
on walls of a porous nature appear equally as efficient as the DDT-
kerosene sprays of the same concentrations on smooth surfaces. On
concrete walls applications of 100 mg. of DDT per square foot gave
excellent control of houseflies throughout the season.
Dusts.--Dusts containing 10 percent of DIDT, applied with a hand
duster in barns just before the cows were milked, killed the flies
present, but there was no noticeable protection a day or two aftoe'-
Ceiling streamers.--Streamers made of cloth and treated with a
5- or 20-percent DDT emulsion killed flies that alighted on them, but
they were not preferred by the flies as resting places. In dairy barns
in eastern Montana, when treated strips of cheesecloth were used, there
was no noticeable reduction of the housefly population, and it was
necessary to resort to other means of control.
Sprays containing 5 percent of DDT in kerosene were applied by
W. G. Bruce to screens of residences at New Smyrna Beach, Fla., for
control of sandflies (Culicoides spp.). Numbers of the flies died
shortly after they passed through the meshes of the screen and before
they were able to take a meal of blood. Protection was obtained also
from 10-percent DDT powder applied on the clothing that was worn about
salt marshes. The powder probably gave less protection than a spray
containing an insect repellent such as dimethyl phthalate or the mix-
ture used by the armed forces.
Dog Flies or Stableflies
Bay-water emulsions of both DDT and DIT residual oil, applied by
S. W. Simmons and E. B. Blakeslee as light surface sprays to infested
marine-grass deposits along the shores of inner bays of northwestern
Florida, effectively controlled breeding of the dog fly (Stomoxy)
calcitrans L.), also called the stablefly. The treatments did not
penetrate the grass to kill the immature stages, but the adult flies
that walked upon the treated surfaces were killed. Plot tests of com-
parative toxicity showed DIDT to be about four or five times as lethal
as the residual oil.
When applied to marine-grass deposits at a concentration of 0.5
percent for DDT, or 2.. to 3 percent for DIDT residual oil (contains
about 22 percent of D, .-DTYT), at the rate of 2 gallons per 100
square feet, 90 to 95 percent of emerging flies were killed. On in-
fested grass treated and subjected to tidal action, 60 percent control
1-:L3 obtained when *r>jsults were compared with those obtained on a
similar untreated plot. The treatment plus the effects of the tide
provided 90 percer.n. control of the fly breeding. Uninfested grass
treated with these sprays has shown complete protection against in-
festation for the period it is susceptible to fly breeding.
Approximately 41 miles of grass distributed along 75 miles of
shoreline were treated by E. B. Blakeslee, in cooperation with
K. D. Quarterman, with either DDT or a DDT residual oil. A total of
7,514 gallons of diluted spray were applied at an average rate of ap-
proximately 180 gallons per mile of grass. The observations suggest
that new deposits of grass accumulate within 2 weeks, and these should
be treated in order to prevent flies from developing in the new
In different localities spray applications of emulsions contain-
ing 5 percent or less of DDT to cattle, horses, and dogs did not pro-
vide any immediate protection against stableflies. The flies gorged
themselves on the treated surfaces, and most of them died within a few
hours after feeding. Protection of animals was obtained from treat-
ments of walls and ceilings of barns and stables, as described for
tests with houseflies. These treatments were equally effective for
both species of flies.
Sprays containing 5 percent of DDT' and dusts containing 10 per-
cent of this chemical were applied to pits of latrines and found to
be ineffective against larvae of the soldier fly Hernetia illucens
(L.). Screens treated with the spray killed adult flies that Ilked
A smear containing 20 percent of DT and a dust containing 10
percent of DDT were used by H. E. Parish for treating wounds of 20
sheep infested with 5-day-old screwworms (Cochlio2Mia americana C. end
P.). The animals suffered no ill effects, and the average period re-
quired for healing was 34 days. Both the smear and the powder pro-
tected the wounds against reinfestation for 21 days. After both treat-
ments reinfestation occurred in half the wounds whereas in sheep
treated with smear 62 (containing diphenylamine) only 40 percent of
the wounds were reinvested. WOT therefore appears to be somewhat less
effective than smear 62, the recommended treatment for protecting
wounds of animals.
American Dog Tick
Because the American dog tick (Dermacentor variabilis (Say))
transmits the eastern strain of spotted fever, it has been desirable
to develop a treatment that can be used on vegetation to free the pre-
mises of residences, parks, and camp sites of these ticks. Emxlsions
containing 0.5 percent of DIOT and 2.5 percent of soluble pine oil gave
a high kill of these ticks. The applications were made at the rate of
about 3 pounds of DDT per acre. Experiments with dusts containing
DDT have not always been successful. Dips and dusts for the infested
animals have not been so satisfactory as the standrad dips and the
ground derris or cube powders containing 5 percent of rotenone.
Brown Dog Tick
A dwelling at St. Andrews, Fla., heavily infested with all stages
of the brown dog tick (Rhipicephalus sangneus (Latr.)) was treated
with IDT by E. B. Blakeslee. About 1/2 pound of powder containing 10
percent of DIDT was applied beneath and behind the baseboards of all
rooms. The dog in the house was treated wtth 15 grams (about 1/2 tea-
spoonful) of the powder on four occasions. There were no apparent Ill
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effects upon the animal or the residents, and within 2 to 3 mont:i the
infestation was brought under complete control. For controlling; light
or moderate infestations, as little as 4 ounces of the 10-percent
powder was found to be sufficient to give control of the infestation
when applied in a small apartment where one dog was kept. One thorough
treatment of a dog hospital brought freedom from brown dog ticks for
almost a year. Sprays containing 5 percent of DDT were just as effec-
tive as powders for treating baseboard crevices.
Poultry houses infested with the fowl tick (Argas miniatus Koch)
were suceesfully treated by H. E. Parish with a residual spray con-
taining 5 percent of DDT in kerosene. The treatment was applied to
the perch poles end to cracks, crevices, and other hiding places of
the ticks. For 3 months following treatment no living ticks could be
found. On account of the long life of this tick, the test will be
observed for any reoccurrences of the infestation.
Gulf Coast Tick
The bite of the Gulf Coast tick (Ambyomma maculatum Koch) is an
important cause of screwworm attack on livestock in the coastal areas
of the Southern States. From about the first of August until the
latter part of October approximately 85 percent of all screwworm in-
festations occur in injuries produced by this tick, and there is need
for a treatment that will remain effective for 10 weeks or more. In
Florida tests were made by W. G. Bruce and A. L. Smith to determine the
effectiveness of a treatment containing 5 percent of DDT in a nondrying
adhesive, which is a form of synthetic rubber, and dibutyl phthalate.
Thif- treatment had been used against this tick by E. B. Blakeslee in
Florida. Dish-mop and paint-brush methods of application were fairly
satisfactory, but the use of the bare hand was faster and afforded a
more complete coverage of the ears of long-haired cattle. On 18 head
of cattle that were wild and difficult to handle, it was almost in-
possible to obtain complete coverage of the ears, and 20 days after
treatment only about 20 percent of the ticks on these animals were
killed. In 7 tests made on as many ranches, representing a total of
250 head of cattle, no screworms developed in the ears of any of the
treated animals, whereas many ticks were present on untreated cattle
ranging in the same pastures.
In Edna and Port Lavaca, Tex., the treatment was applied by
H. E. Parish and C. S. Rude in several experiments. On one ranch 592
head of mixed cattle having an average infestation of 4.49 ticks per
ear were treated. At the end of 2 weeks the number was reduced to 0.5
tick per ear and only 10 percent of the animals required another
treatment. Four weeks later there were 1.85 ticks per ear and one-
third of the animals needed another treatment. The untreated animals
on the ranch had 5.95 ticks per ear 2 weeks after the treating date,
and 14 ticks per ear at the end of 4 weeks.
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On another ranch 778 head of mixed cattle averaged 4.6 ticks per
ear when treated, and 2 weeks later averaged 0.2 tick per ear. Dur-
ing the same period a treatment of 35 horses reduced the number of
ticks per ear from 3.4 to 0.5.
Lone Star Tick
The clothing of several volunteer workmen in woods in southern
Georgia was treated by C. N. Smith with a 10-percent DTI powder or a
5-percent 2DX1 emulsion and worn by them on a range infested with the
lone star tick (Amblyomna americanum (L)). The treatments did- not
prevent attachments and engorgements of the ticks. In prelliLrL. 7
tests a 5-percent DDT powder applied to grass land at the rate of 3
pounds per acre killed all stages of this tick, and 1 pound of iL'
per acre applied in a pine-oil emulsion was equally effective, Dips
with 1 percent of DT in a pine-oil emulsion showed some promise when
used for dipping infested dogs, but did not kill the larvae that were
Relapsing Fever Tick
Specimens of the tick thas carries relapsing fever, Ornithodoros
turicata (DPg's), were treated in the laboratory with spray emulsions
of DIM furnished by the Bureau to Neal M. Randolph, of the Texas
State Board of Health. Sprays containing 10 percent of DDT killed 90
percent of the ticks, When applied as a direct spray, the mortality
occurring gradually after 6 days and being complete 9 days after
treatment. A I-percent DDT spray applied to the inside of cages con-
taining no debris or litter gradually killed 90 percent of the ticks
at the end of 30 days. Sprays applied to clay floors in the cages
killed about 20 percent of the ticks. These findings suggest that
DDT sprays may kill many of the ticks in caves. Inside of dry caves,
however, under natural conditions, such a treatment could not be ex-
pected to eradicate an infestation.
Winter Horse Tick
A wash used by H. E. Parish and C. S. Rude on 35 horses infested
with the winter horse tick (Dermacentor nigrolineatus (Pack.)) con-
tained 0.9 percent of DT in a soluble-pine-oil emulsion. It killed
all the ticks on the horses and protected them from reinfestation for
about 60 days. There was no apparent injury to any of the horses; on
the contrary there appeared to be an improvement in the skin and hair.
Similar washes with less DDT did not kill all the ticks present.
External Parasites of Rats
At Savannah, Ga., H. K. Gouck treated four poultry-produce stores
for control of fleas, mites, and lice on rats. As soon as some rats
were caught from these premises, they were killed and placed in bags
and fumigated. The parasites were then collected and retained for
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identification. Specimens were identified as Nosopsyllus fasciatus
(Bosc.), Liponyssus bacoti (Hirst), Xenopsylla cheopis (Ro-t--ch.).
Ctenopsyllus segnis (Schon.), Echidnophaga gallinacea (Westw.),
Laelaps hawaiiensis (Ewg.), and P2oplax spinulosa (Burm.).
Store A was treated by means of a dust gun, using 3 3/4 pounds
of 10-percent DIT powder; store B was treated with 5 1/4 pounds of
aDT; and store C was treated by using 24 paper cylinders each contain-
ing 25 grams of MIT. Four days after treatment there was a decrease
of 90 percent in fleas, 100 percent in mites, and 73 percent in lice
in store A; and a decrease of 100 percent in fleas and 92 percent in
lice in store B, all as compared with the number of insects on rats
before treatment. In store D (untreated) there was an increase of 2
percent in fleas, 65 percent in mites, and a decrease of 78 percent
This study suggests that PIM dusts are promising as treatments
for control of external parasites of rats. Further observations are
being made to determine the period of effectiveness of the treatments.
Ant hills built by one species of Tapinoma between the bricis of
a drive-way and between stones of a terrace were promptly abandoned
when DMT powder was placed on them. The treatments were made in June
and the nests remained unoccupied for the remainder of the season.
During July and September numerous ant colonies were treated with 10
percent of DDT in pyrophyllite. A small amount of the powder placed
around the entrance holes of the nests of fire ants (Solenopais
emina~t (F.)) resulted in a complete disappearance of the ants. When
undiluted technical DTI was placed in very small amounts about the
rurfaco of two large nests of carpenter ants (Qponotus sp,), in soil
against a house foundation, all the ants disappeared. A small amount
of a 10-percent DDTr-pyrophyllite powder was dusted over trails of the
crc .- ant (Paratrechina longicornip (Latr.)), and a spray containing
5 percent of DDT was applied to floor areas infested with this
pe' iLes; in both cases the ants disappeared for more than 3 months.
In residences sprays containing 5 percent of DDT in kerosene
killed all ants hit with the spray, but some of these treatments gave
only temporary relief. The treatments were Ineffective against ants
that did not make trails into the buildings because it was impossible
to anticipate their route of travel and thus treat the proper places.
They were more effective when applied to ant trails but did not pre-
vent all the ants from foraging in kitchens.
Kerosene sprays containing 5 percent of DOT have been used ex-
tensively on beds of Army and Navy personnel for control of bedbugs.
Recently a large number of tests were undertaken, in cooperation with
the National Pest Control Association, in about 20 cities of the
United States to determine the efficacy of the treatments for use in
I" 13 /
apartments, hotels, and residences. Deodorized-kerosene sprays con-
talning/lO, percent of DDT in pyrophyllite were furnished to pest con-
trol orators, together with suggestions on methods of application.
Mattresses, pillows, bedsprings, and crevices about the beds were
treated with the spray or the dust. From these tests it was learned
that double beds could be treated effectively with 3 liquid ounces of
spray or with 2 ounces of the powder. The treatments persisted long
enough to kill the bugs that came out of hiding to obtain a meal of
blood. In theaters and in railroad cars, on seats that were infested
with bedbugs, sprays were apparently used with results equal to those
obtained on bedding.
Thcperiments were conducted against the American cockroach (Peri-
_Aqet_ amerlcana (L,)), the German cockroach (Blattella germanica,
(1.)), and the brown-banded roach (Supella pellectilium, (Serv.j) in
cooperation with government agencies and pst control operators in-
terested in the control of cockroaches in civilian food establishments
and kitchens. The experiments were carried out under various condi-
tions with 5 percent of DDT in kerosene or emulsions, or with 10 per-
cent of DDT in pyrophyllite. It appeared that any one of the treat-
ments was as effective as sodium fluoride when applied by trained per-
sons to the proper places. Within an hour or 2 after treatment some
dead roaches were found and many living ones showed the effects of the
treatment, and after about 7 days the populations of the roaches were
greatly reduced. In the South, where roaches ofter develop outside of
buildings and migrate into kitchens, and also to prevent importation of
new roaches in grocery or other deliveries, it was important to main-
tain a residual treatment in favorable places to kill the roaches and
to keep new ones from becoming established. Because cockroaches like
to walk upside down beneath refrigerators, table tops, and shelves, a
spray was used in conjunction with any dust treatments made in kitch-
ens. Sprays were used to good advantage in cupboard drawers and other
partlV closed spaces against the German roach, or in radios and simi-
lar places for the brown-banded roach. Kerosene sprays should be used
only in places where they offer no fire hazard.
In experiments made by A. W. Lindquist in Florida and C. N. Smith
in Georgia, powders containing 10 percent of DDT in pyrophylllte
applied at the rate of about 10 grams (1/3 teaspoonful) for an average-
size dog killed the flea Ctenocephalidee canis (Curt.) within 10 to 15
minutes to a few hours. The treatments temporarily stimulated the
fleas to become active on the animal, and some dogs continued to scratch
for about an hour. A single treatment protected the animals from
further infestations for 4 to 7 days. These treatments were supple-
mented by dusting or spraying of infested bedding and premises at the
rate of 1 pound of a 5-percent DDT powder or 1/2 gallon of a spray con-
taining 5 percent of DDT per 1,000 square feet. The dusts containing
1 percent of DDT and the pine-oil emulsions containing 0.2 percent of
UNIVERSITY O FLORID
-14 3 1262 09238 7'363
DDT were used satisfactorily on lawns infested with fleas, but oil
sprays often burned the grass. Single treatments of dogs and kennels
yielded satisfactory control of fleas, including the sticktight flea,
(Echidnophaga gallinacea (Westw.)). Cats often became sick from lick-
ing the powder from the hair, and some of them ingeeted enough DDT to
cause their death.
Wasps and Hornets
Colonies of wasps were destroyed by Helen Sollers in many places
in Washington, D. C., and vicinity, with applications of a 10-percent
DDT-pyrophyllite dust into the entrance holes of the nests. Treatment
of a nest of Vespula maculifrons (Buyss.) established beneath a rear
porch between s floor and ceiling destroyed the colony. Where yellow
Jackets (Vespa sp.) occupied a gourd that had been used as a wren's
nest, a dust treatment freed'the gourd of the pests within 24 hours.
A similar treatment of two nests of Vespila diabolical (Sauss.) was in-
A white-faced hornet's nest over the entrance to a garage, treat-
ed by the same method, was found to be abandoned the following morning.
Wasps (Pollstes sp.) nesting beneath a doorstep in a cellar area- "-'
and near an electric-light fixture on a porch, were dusted with this /
powder with excellent results. No Polistes were seen after 12 hours.
It appears that a 10-percent DDT-pyrophyllite mixture will prove
useful for control of wasps' and hornets' nests.