of external parasites of
livestock in florida...
JAMES E. BROGDON
LEONARD E. SWANSON
Control of External Parasites of Livestock
External parasites, including lice, ticks, horn flies, house flies,
stable flies, cattle grubs, horse flies, deer flies and mosquitoes, pre-
sent a serious problem to the beef and dairy industries of Florida.
These pests are most prevalent during spring and summer
months. In Florida's warm climate, however, many are a prob-
lem the year around.
Insecticides are available that will control most of the major
external parasites of livestock when applied thoroughly and at
the proper times.
Several kinds of lice attack livestock in Florida.
Animals infested have a hair coat, with a rough,
coarse appearance, and do not reach maximum pro-
-duction or gain properly. They rub against posts,
fences and trees, lick themselves and chew their
tails (a sign of tail lice). Lice spend the entire
life cycle on the host animals and are more preva-
lent during winter and spring. The best time to control lice is
in the fall and winter.
1. Sucking lice, which feed on blood, include (a) the long-
nose cattle louse (on head, neck and brisket) ; (b) the short-nosed
cattle louse (on head, neck and brisket) ; (c) the blue louse (in
rings on face, muzzle and around the eyes) ; and (d) the cattle
tail louse (found principally in brush of tail and around the
2. One kind of biting louse, known as the cattle biting louse,
feeds on skin and hair, causing itching and irritation.
Only one kind, known as the hog louse, is found on hogs. It
does not attack other animals. Hog lice are found primarily on
the inside of the upper part of the legs, in the folds of skin
about the neck, and inside the ears.
C.-Lice of Horses and Mules:
The horse biting louse and the horse sucking louse attack
these animals. Both kinds are most prevalent about the head,
neck, withers and base of the tail.
D.-Lice of Sheep and Goats:
A biting louse and the goat sucking louse attack sheep and
In Florida, ticks are principally pests of
cattle, especially range cattle. The most
common are the Gulf Coast tick, lone star ,
tick, black-legged tick and cattle tick. The '
sheep tick (sheep ked) is a pest of sheep
These pests are blood suckers that re-
main on animals except when laying eggs.
They breed in fresh manure. Horn flies,
which congregate primarily on the withers
and backs, are more numerous on sick ani- f
mals and on dark-colored animals. These
pests alone may cost the cattleman 20 to
30 pounds of beef per animal each year. 1
B.-Stable Flies (Dog Flies):
These insects are blood suckers with a severe bite. They
breed in decaying organic matter, including straw piles, refuse
from packing sheds, citrus refuse, etc. Stable flies have the
habit of congregating on the sides of buildings and on fences
where residual sprays can be effectively applied.
Control by insecticides is not completely satisfactory, especially
on beef cattle. Recommendations for dairy animals appear in
the chart on page 9. Breeding areas must be eliminated. These
efforts should be supplemented by applying residual sprays to
the outside of barns, to board fences, posts and similar resting
places. Materials that may be used include malathion, diazinon,
ronnel (Korlan), lindane, methoxychlor, DDT, toxaphene or other
approved insecticides. Follow recommendations on the label.
N C.-House Flies:
House flies do not bite but annoy ani-
mals and may spread diseases. They
breed in fermenting animal and vege-
table matter and other filth. Screens,
insecticides and sanitation are of major
importance in house fly control. Since
house flies have been able to develop re-
sistance to most of the newer insecti-
cides, there has been a renewed interest
in sanitation in fly control programs. This means getting rid
of the breeding places.
Control.- Good sanitation should be supplemented with in-
secticides. Chlorinated hydrocarbon insecticides including DDT,
methoxychlor, lindane, chlordane, dieldrin and others are of
little or no value in controlling house flies in Florida. Though
some resistance has also been shown to organic phosphate in-
secticides including malathion, diazinon, Dipterex, ronnel (Kor-
lan) and others, these materials are still useful in house fly control
programs. Follow directions on the insecticide label for mixing
and applying these materials as residual sprays.
Poisoned baits control house flies in some places where sprays
fail, particularly in unscreened dairy barns and in other farm
buildings. If properly applied, they can be used in most farm
buildings without harming domestic animals. Ready-to-use dry
and liquid baits containing organic phosphate insecticides, in-
cluding malathion, diazinon, ronnel (Korlan), Dipterex, DDVP
and possibly others, may be purchased commercially. If not
available ready-prepared, some insecticides, including malathion,
diazinon and ronnel (Korlan), may be purchased in the con-
centrate form and mixed and applied according to recommenda-
tions on the container label.
Space sprays containing pyrethrum, allethrin and similar
materials can be used daily as a contact spray for adult flies.
These materials have little residual effect and are best in closed
D.-Horse Flies and Deer Flies:
About 65 species of these flies are found in Florida. These
blood-sucking insects are vicious biters that breed in wet areas.
There is no practical control for these pests on beef animals.
Sprays containing pyrethrum plus a synergist are effective (see
in chart under dairy cattle), but have to be applied several times
a week. Animals should be kept out of wet areas as much as
possible during the fly breeding season (spring until late fall).
E.-Heel Flies (Warbles, Wolves, Cattle Grubs):
Only one species of
heel fly is found in Flor-
ida. It is not as serious
a pest here as in many
other states. Cattle
often are seen in the
spring (February, March .
or April) running from
heel flies or standing in
water to keep the flies .; '
from laying eggs which
are usually attached to
hairs below the hock.
The eggs hatch into tiny larvae or grubs that bore into the flesh
and spend several months tunneling in the body. The grubs
move up through the animal tissues and appear in the backs of
cattle in November, December and January. In addition to con-
trols in the chart, see ronnel (Trolene) and Co-Ral, pages 6 and 7.
Three species attack horses. These insects lay eggs on hair
about the nose or lips, under the throat or jaw, and on the lower
legs. The maggot or larval stage, which lives in the digestive
tract of the horse, causes injuries to the tongue, lips and the lin-
ing of the stomach and intestine. A horse badly infested with
bots has a rough hair coat, becomes thin and goes off feed as a
result of digestive disturbances.
Carbon disulfide is the most effective treatment given either
in gelatin capsules or by a stomach tube. Carbon disulfide is a
gas-producing liquid which if improperly administered can cause
death to the animal by strangulation. Therefore, veterinary
services are recommended for control of these pests.
Several kinds of maggots i
infest wounds of warm- .
blooded animals in Florida, s '). '
but the one that feeds only on
live flesh is the primary screwworm. This pest was not found
in Florida before 1934. The State of Florida and the U. S.
Department of Agriculture, in cooperation with other South-
eastern States, have eradicated the screwworm from the South-
east through mass releases of sterile male flies.
Of equal importance to the eradication of screwworm is the
prevention of reinfestation. Since this pest will not normally
migrate from the infested Southwestern states into the South-
east, inspection stations have been established along the Missis-
sippi River to provide for thorough inspections and proper treat-
ment of all animals moving from infested states into the South-
In Florida your County Agricultural Agent or local screw-
worm inspector should be notified promptly of any suspected
screwworm case in livestock, pets or wildlife. Make a record of
the infestation and save samples of the eggs and maggots from
the wounds. Keep the maggots in a bottle or other small con-
tainer filled with water and keep the eggs dry, in a pillbox or
similar container, until the County Agent or screwworm inspec-
tor calls for them.
There are a number of good remedies available for treating
wounds, but EQ-335 or Smear 62 is preferred. Repeat treat-
ments until the wound is healed.
Several kinds of mosquitoes attack livestock. They must
have water in which to breed. Mosquitoes have piercing mouth-
parts and suck blood. There is no practical insecticidal control
for these pests on range cattle.
f Different species of mange and scab
mites attack horses, swine, cattle and
sheep. Included are Psoroptes, Sar-
coptes, Chorioptes and Demodex mites.
l'These pests are too small to be seen
With the naked eye. They burrow their
I j 1 heads into the skin and suck blood,
Y causing severe irritation.
NEW ORGANIC PHOSPHATE INSECTICIDES
Co-Ral, an organic phosphate insecticide with systemic action,
is available in 25% strength as a wettable powder to be applied
as a spray. It should not be given internally.
When properly applied as a spray, Co-Ral kills cattle grubs
in the body of the animal by being absorbed and circulated with
body fluids. Though this material is generally effective against
cattle grubs when applied from the first of June to October, the
preferred time of application is June through August.
Co-Ral may be used also as a spray for the control of screw-
worms, horn flies, lice and ticks on beef cattle; screwworms, lice,
keds (sheep ticks), and ticks on sheep and goats; and lice and
screwworms on swine. Follow directions and precautions on the
Trolene, which also is an organic phosphate insecticide with
systemic action, refers to the purified grade of ronnel. It is
available as a bolus (a large pill) containing 40% ronnel, to be
administered by mouth for the control of cattle grubs in beef
cattle and non-lactating dairy animals. The preferred time of
treatment is June through August. Follow directions and pre-
cautions on the manufacturer's label.
Korlan refers to the technical grade (not purified) of ronnel
and is formulated as a 25% wettable powder, 12% and 24%
emulsifiable concentrates and 5% screwworm smear. Korlan is
recommended for the control of horn flies, lice, ticks and screw-
worms on beef cattle and non-lactating dairy animals; lice, keds
(sheep ticks), and screwworms on sheep and goats; and lice on
swine as a spray only. It should not be given internally. Follow
directions and precautions on the manufacturer's label.
INSECTICIDE RESIDUE TOLERANCES
The Food and Drug Administration has established residue
tolerances for certain insecticides in the meat of certain animals.
When these and other approved insecticides are applied accord-
ing to recommendations, the pests should be effectively controlled
and the animal products will be safe for food. The following
tolerances have been established:
DDT-7 parts per million in the fat of meat of beef cattle,
swine, sheep and goats.
Toxaphene-7 parts per million in the meat of beef cattle,
swine, sheep and goats.
Methoxychlor-3 parts per million in the fat of meat of beef
cattle, swine, sheep and goats.
Malathion-4 parts per million in the meat of beef cattle,
swine, sheep and goats.
RECOMMENDATIONS FOR CONTROL OF EXTERNAL PARASITES OF LIVESTOCK
(When these insecticides are applied according to recommendations, the pests should be effectively controlled and the animal
products will be safe for food.)
Materials and Formulation
100 Gals.) Remarks
Lice Toxaphene-40% w.p.
Ronnel (Korlan), Co-Ral
Horn flies Toxaphene-40% w.p.
Ronnel (Korlan), Co-Ral
Ticks Toxaphene-40% w.p.
Ronnel (Korlan), Co-Ral
(see pages 6 and 7)
(see pages 6 and 7)
(see pages 6 and 7)
Complete coverage is essential. Repeat after
2 or 3 weeks if needed. Do not treat sick
animals. Do not treat calves under 1 month
of age with malathion spray or toxaphene
dip. Do not apply lindane within 30 days
or toxaphene within 28 days of slaughter.
No time limitations for malathion or me-
To backs every 3 weeks or as needed. See com-
ments above under lice concerning limita-
tions of spray materials. Also see Back-
rubbers, page 10.
10 lbs. Immerse or spray animals thoroughly. Re-
1 lb. peat after 2 or 3 weeks if needed. See com-
............ ments above under lice for limitations of
Rotenone-5%9, powder 71/2 lbs.
Ronnel (Korlan), Co-Ral (see pages 6 and 7.
Do not apply to calves under 6 months of age
at this dosage. Repeat applications may be
71/2 lbs. Treat when grubs first appear and repeat 1
to 3 times at 30 day intervals. Dusts and
washes may be used in small herds.
There is no practical insecticidal control of these pests on beef cattle. See discussion on horse flies and
deer flies, page 4. Also see controls below under dairy cattle.
See discussion on house flies, page 4, and stable flies, page 3.
See discussion on screwworms, page 5.
Rotenone-5% w.p. 1-2 lbs.
Pyrethrins + synergist* (see remarks)
1-2 lbs. Spray containing 0.025% pyrethrins + 0.25%
piperonyl butoxide. Spray animals thor-
oughly. Repeat in 2 to 3 weeks or as needed.
Horn flies One tablespoon of 50% methoxychlor w.p. or 3 tablespoons of 5% malathion dust per cow rubbed into
hair on back and neck every 3 weeks for methoxychlor and 10 to 14 days for malathion. Treadle or hand
sprayers containing oil solution of (a) pyrethrins + synergist*, (b) 3 to 5% Lethane 384, or (c) 3
to 5% Thanite can be used. Also see Backrubbers, page 10.
Cattle Grubs Rotenone as for beef cattle.
See discussion on Screwworms, page 5.
.05 to .1% Pyrethrins + .5 to 1% synergist* spray prepared from commercial concentrate by adding
water. Apply 1 to 2 quarts per animal every 2 to 3 days; or oil solution or emulsion concentrate of
1% pyrethrins + 10% synergist* at 1 to 2 oz. per cow daily as a mist spray; or 3 to 5% Lethane
384 or Thanite oil solution at 1 to 2 oz. per cow daily as a mist spray.
Discussion on house flies, page 4.
Sheep Lice, Ticks, Toxaphene-40% w.p. 10 lbs. 5 lbs. Immerse or spray animals thoroughly. Re-
and Keds Lindane-25% w.p. Iz/ lbs. 1 Ib. peat (except DDT) in 2 or 3 weeks, if needed.
Goats (Sheep ticks) DDT-50% w.p. 8 lbs. 4 lbs. Do not use any of these materials on milk
Malathion-25% w.p. 16 lbs. ------animals. Do not apply toxaphene within 28
Ronnel (Korlan), Co-Ral (see pages 6 and 7) days, or DDT or lindane within 30 days of
Mites slaughter. No time limitation for malathion.
(Mange) Lindane as above under lice and ticks
Screwworms See discussion, page -
Swine Lice Lindane-25% w.p. 2 lbs. 2 lbs. Immerse or spray animals thoroughly. Re-
Toxaphene-40% w.p. 10 lbs. ............ peat in 2 or 3 weeks or as needed, except for
DDT-50% w.p. 8 lbs. 8 lbs. DDT (one treatment only). Days before
Malathion-25% w.p. 16 lbs. ........... slaughter same as for lice on Sheep and
Methoxychlor--50% w.p. 8 lbs. 8 lbs. Goats above. Also see Backrubbers, page 10.
Ronnel (Korlan), Co-Ral (see pages 6 and 7)
(Mange) Lindane as for lice-repeat in 2 weeks if needed
Screwworms See discussion, page 5.
Mules and Lice, Mange,
Horses Flies, Bots, See recommendations for beef cattle. For bots, veterinary services recommended.
Note: W.P. is symbol used for wettable powder. Equivalent amounts of emulsifiable concentrates formulated for use on livestock
may be used. Follow recommendations on the insecticide label.
Piperonyl butoxide or other approved synergist.
Lindane-7 parts per million in the fat of meat of beef cattle,
sheep and goats; 4 parts per million in swine.
Certain other insecticides, including ronnel and Co-Ral, have
been accepted for use on animals on a no residue basis, but if
used according to recommendations should not present a residue
To avoid excessive residues use the insecticides recommended
at the time recommended and in the amounts recommended.
APPLICATION OF INSECTICIDES
The control of external parasites of livestock depends upon
careful mixing and application as well as upon using the right
insecticides. Always read the label carefully and completely and
be sure you understand all of the directions, limitations and pre-
cautions before using. Never use more insecticide than is recom-
mended. Young animals, calves in particular, are susceptible to
overdoses of some pesticides. When using an emulsifiable con-
centrate, be sure it mixes uniformly with the water. Use only
emulsifiable concentrates prepared for use on livestock.
Sprayers.-For a large number of cattle, power sprayers
that operate at approximately 200 pounds of pressure per square
inch are generally suitable. The sprayer should be equipped with
an agitator to keep the spray well mixed and with an adjust-
able spray nozzle. For treating a few animals a small portable
power rig can be used. In using a power sprayer, direct the
spray back into the tank until proper mixing is assured. Knap-
sack or small air-pressure sprayers may be used, but it is more
difficult to thoroughly wet animals with long, dense hair. Also
some of these sprayers do not have agitators and will require
occasional shaking to assure a properly mixed spray, especially
with wettable powders.
Dipping vats are not widely used in Florida. It is usually
more convenient to move the sprayer to the livestock than to
round up all animals and drive them to one central location.
Spraying is not as hard on livestock as putting them through a
vat. In addition, there are few accurate methods for determi-
ning the concentration of an insecticide in a dipping vat after it
has been allowed to stand for a period of time.
Backrubbers of various kinds can be made or purchased com-
mercially for control of horn flies. These devices will aid in the
control of certain other pests, including lice. Cattle treat them-
selves by walking under and rubbing against the backrubbers.
This is a tremendous saving in labor and spray materials.
CONSTRUCTION OF CABLE-TYPE BACKRUBBERS
STEP 2 TIE 6 TO 8 INCHES APART WITH HEAVY TWINE
Correct location of the backrubber is very important. Under-
brush will compete with backrubbers and locations containing it
should be avoided. No one can prescribe the exact location of
the rubbing units without a study of the particular pastures and
loafing places and habits of the cattle. Backrubbers should be
placed in locations where cattle congregate, such as mineral or
salt stations, feeding pens or near watering areas. It takes a
while for cattle to become accustomed to backrubbers and to
learn to use them.
Various kinds of backrubbers with storage cylinders to pro-
vide a continuous source of insecticide are available commercially.
For an example, see picture on the cover.
Backrubbers can be constructed on the ranch (see illustra-
tions A, B and C, page 11). They may be placed between posts
that are 15 to 20 feet apart. Posts should be 6 inches in diameter
and 8 feet long and should be pressure treated or of wood which
is slow to rot. They should be 41/ feet above ground and well
braced. Stretch a cable, chain or heavy wire (9 gauge) between
the posts and allow to sag within 1 to 11/2 feet of the ground. A
core made of three strands of barbed wire wrapped either with a
fourth strand of barbed wire or heavy wire (9 gauge) is excellent
if properly made and maintained. Attach the ends at a height
of 4 feet on the posts. Wrap sacks on cable, chain or heavy wire
as shown in the illustration, page 11. Wrap sack No. 1 once
over cable. Follow with No. 2, then No. 3. Go back to No. 1
and repeat the process until all sacks are completely rolled. Tie
each overlapped joint securely with pieces of heavy twine, then
tie 6 to 8 inches apart between the joints as shown in the illus-
tration. Modifications of the diagrams shown here may be made
to accommodate the management practices of any farm. Brace
wires and posts may be wrapped with sacks and treated as shown
in the illustrations.
Insecticides for Backrubbers to control hornflies on cattle not
being milked include toxaphene, methoxychlor, DDT, malathion
and ronnel (Korlan). Toxaphene continues to be one of the best
insecticides for control of horn flies. Reports from some areas
indicate that DDT is not as effective against this pest as in the
Pour about 1 gallon of one of the recommended solutions
slowly and evenly on 15 to 20 feet of burlap backrubber. Retreat
the backrubber every 2 to 3 weeks or as needed. One backrubber
should be available for each 50 to 75 animals.
Wettable powder formulations of insecticides are not suitable.
Do not spray or pour oil solutions directly on cattle. If barbed
wire is used, be sure the barbs are thoroughly covered at all times
to prevent injury to animals.
INSECTICIDES TO USE FOR BACKRUBBERS FOR BEEF CATTLE
Amount fr Minimum days-
Insecticide gallon ** last app'n to
60-65% Toxaphene E.C.* % pint 28
25% DDT E.C.* 1 quart 30
25% Methoxychlor E.C.* 1 quart No time limitation
57% Malathion E.C.* 1/ pint No time limitation
12% Ronnel (Korlan) E.C.* 1 pint 56
24% Ronnel (Korlan) E.C.* 1/ pint 56
*E.C. = Emulsifiable concentrate. Wettable powder formulations are not
**Oils recommended are fuel oil, diesel oil or kerosene (not crankcase or
Do not apply these mixtures to lactating dairy cattle. For
cows being milked use a concentrate containing pyrethrins plus
a synergist and mix according to recommendations on the label.
All insecticides are poisonous to man and animals. Do not
contaminate feed or water. Wash off any insecticide spilled on
the skin. Launder clothes that may become contaminated.
Store insecticide in the original container out of reach of chil-
dren, pets and livestock. The use of insecticides not recom-
mended or in concentrations greater than those listed in this
circular may result in injury to animals or insecticide residues
in excess of legal tolerances. Always read the insecticide label
carefully and completely before opening the container. Observe
Appreciation is expressed to workers of the Florida Agricultural Experi-
ment Stations, Florida Agricultural Extension Service, Insects Affecting
Man and Animals Research Branch and Pesticide Regulation Branch, Agri-
cultural Research Service, USDA, and to the Entomologist, Federal Extension
Service, for helpful information and suggestions used in this circular.
Considerable information was taken from Agriculture Handbook No. 120,
ARS, USDA, Revised March 1960, and subsequent releases.
The use of trade names in this publication is solely for the purpose of
providing specific information. It is not a guarantee or warranty of the
products named and does not signify that they are approved to the exclusion
of others of suitable composition.
SCIENTIFIC NAMES OF CERTAIN PESTS OF LIVESTOCK
DISCUSSED IN THIS CIRCULAR
General (more than one animal):
Common cattle grub
Long-nose cattle louse
Short-nose cattle louse
Cattle tail louse
Cattle biting louse
Gulf Coast ticks
Lone star tick
Horses and Mules:
Horse biting louse
Horse sucking louse
Sheep and Goats:
A biting louse
Goat sucking louse
Ixodes ricinus scapularis