STATE I-LANT aJ ?",
E-481 June 1939
United States Department of Agriculture
Bureau of Entomology and Plant Quarantine
DIPHENYLAMINE AS A WOUND PROTECTOR AGAINST THE
SCREWWORM, COCHLIOMYIA AMERICANA C. AND P.
By Roy Melvin, Henry E. Parish, Edward F. Knipling,
and Raymond C. Bushland,
Division of Insects Affecting Man and Animals
A crystalline chemical substance known as. diphenylamine has been
found to be very effective for protecting wounds of livestock from becoming
infested with screwworms and for treating wounds infested with these maggots.
The value of diphenylamine for the control of screwworms was dis-
covered after extensive tests had been made with it and a large number of
other chemical compounds on several hundred sheep, goats, and cattle under
ranch conditions in southwestern Texas. l/
Diphenylamine is not a strong fly repellent and does not entirely
prevent flies from laying their eggs on wounds, but it kills the tiny screw-
worms hatching from these eggs before they can injure the tissues. It has
been shown to be greatly superior to pine tar oil, bone oil, and many other
fly-repellent substances commonly used for the prevention of screwworm in-
festations. Not only does this material serve to protect wounds against
infestation, but it will kill the young worms up to 3 days old that may be
present in a wound. It cannot be depended upon, however, to kill screwworms
that are more than 3 days old. 2/
1/ Circular E-480, entitled "Results of Studies on Diphenylamine as
a Wound Protector against ihe Screwworm, Cochliomyia americana C. and P.,"
gives more detailed information on the experimental work leading to the
discovery of diphenylamine as a screwworm remedy.
2/ Experiments carried on by the Bureau of Entomology and Plant
Quarantine indicate that there are several other crystalline chemicals which,
if used in a similar way, may be even more effective than diphenylamine in
the control of screwworms. Further investigations of these are being
undertaken as rapidly as possible to determine their practical value; how-
ever, because diphenylamine has been proved to be so much superior to the screw-
worm remedies now in use, it has been decided to release information concern-
ing it, even though better chemicals may be found later.
How to Use Diphenylamine in Treating Wounds
of Animals for Screwworm Control
The following steps are recommended for obtaining the best results
with diphenylamine in preventing screwworm infestation in uninfested wounds
and for treating animals already infested:
1. For protecting uninfested wounds against screwworms:
In wounds freshly made by such operations as castrating, ear marking,
docking, and dehorning, in older wounds of this kind, or in those caused by
other injuries, provided the wounds are not infested with screwworms, enough
diphenylamine should be used to cover the injured tissues completely. In
the case of castrations it is applied immediately after the removal of the
testes, and a little of the material should be pushed into the scrotum. In
wounds that are bleeding freely, as is the case in dehorning, it is desirable
to take more time for the treatment by putting on small quantities of the
chemical at frequent intervals and holding it in place with the hand or ap-
plicator for several seconds, until bleeding is reduced and there is no
longer danger of most of the chemical being washed away by the flow of blood.
In treating docking cases, a handful of the chemical is simply applied
to the fresh wound and held in place with the hand for about 30 seconds.
Fresh applications of diphenylamine should be made to the wounds every 3
days until they heal.
2. For treating wounds infested with screwworms;
(a) Swab the wound with clean cotton to remove pus, blood, and serum.
Spray a small amount of benzol (commercial 90 percent) into all parts of the
wound with a rubber-bulb syringe or similar applicator to stop the flow of
blood and serum.
(b) Add more benzol and plug the opening of the wound with cotton.
The excess benzol will be absorbed by the cotton, and the fumes will be con-
fined to the cavity of the wound. The fumes of benzol will kill all screw-
worms that breathe them, regardless of their age. Leave the cotton plug in
the wound for at least 3 minutes; then remove it, and, with a pair of blunt-
pointed forceps, pick out most of the larger dead worms, taking care not to
(c) Apply diphenylamine freely to the entire wound, making sure that
all pockets of the wound are filled and that the entire area is covered.
(d) Re-treat all wounds at least every third day with diphenylamine
until they are healed. Benzol need not be used in re-treating on this
schedule, as diphenylamine will kill all worms that have hatched since the
previous treatment. If large worms (over 3 days old) are present, they
indicate that the animal was overlooked or improperly treated with diphenyla-
mine the last time. In such cases the use of benzol will again be necessary
to kill the worms.
Precautions to be Taken in Using Diphenylamine
for Screwworm Control
1. Diphenylamine must be finely ground before it is effective as a
screwworm killer and before it will give good results in protecting '*:our.ds
from infestation. It should be of about the finenes.s of fine granulated
sugar. The condition of diphenylamine as used in the dye industry is much
too coarse to be suitable for the treatment of screwworm cases, and it must
be reground before being applied to wounds.
Diphenylamine does not repel flies or prevent them from laying eggs on
the wound, but by killing the tiny mr.aggots after they hatch it pre'.'ents the
wound from becoming infested. To accomplish this the particles of the chem-
ical have to be very small so that they can be easily devoured by the worms
or brought in close contact with them. Some of the manufacturers of di-
phenylamine are making arrangements to furnish this material of suitable
fineness for use against screwworms. In general, grinding at the factory
is superior to home grinding. If the livestock owner does not w.'ant to go
to the trouble and expense of grinding the material himself he should, when
purchasing it, specify that at least 50 percent of it must be fine enough to
pass through a screen having 40 meshes to the inch and that at least 90
percent must be fine enough to pass through a 20-mesh screen,
S 2. Diphenylamine has a tendency to "cake," especially at high tem-
peratures, when left standing in containers for any appreciable length of
time. In this condition it is not suitable for application to wounds. If
it cakes to such an extent that it cannot be readily crushed with the hands,
it should be restored to its original fineness by regrinding. Storing the
material in a cool place in tight metal or wooden containers and not allowing
it to be exposed to the direct rays of the sun will tend to prevent it from
The Bureau of Entomology and Plant Quarantine is experimenting with
methods whereby diphenylamine of a suitable finesess and which will not cake
may be produced and be made readily available commercially. It is expected
that in a short time the objectionable properties of diphenylamine will be
3. In tests with diphenylamine on a large number of sheep and goats
and a few cattle, horses, and hogs, this material has not been found to be
harmful to any of these animals. Furthermore, in tests in which Dr. W. C.
Mitchell of the Bureau of Animal Industry cooperated and in which large
doses of diphenylamine were administered to sheep, goats, hogs, and cattle
as a drench, by feeding, and in large fresh wounds, no ill effects whatever
Despite this evidence of the nonpoisonous nature of diphenylaine,
precautions should be taken to avoid its being eaten by i.an or animals.
When handling it in the treatment of animals for the control of screwworms,
for any continuous length of time, it is advisable for the operator to wear
gloves or to apply it to the wounds with a spoon or other applicator, and
to avoid getting the material into the mouth, eyes, or nostrils.
4 3 1262 09236 7035 /
Where Diphenylamine may be Obtained
Diphenylamine is manufactured in large quantities for use in the dye
industry, but its use as an insecticide for the control of screwworms is a
new development; consequently livestock owners are not generally informed as
to where it may be obtained. For the information of those who desire to
purchase it for the control of screwworms there is given below a list of
companies which manufacture it and which may be interested in preparing the
material in suitable form for this purpose. No claim is made that the list
is complete, nor is any guarantee here expressed or implied for the products i
of the companies listed. .
E. I. Du Pont de Nemours & Company, Inc., Wilmington, Del. ;
Lederle Laboratories, Inc., 30 Rockefeller Plaza, New York, N. Y. g
Eastman Kodak Company, Chemical Sales Division, Rochester, N. Y. "i
The Dow Chemical Company, Midland, Mich.