E-542 June 1941
AGRICULTURE ~T LN OR
CONTROL OF DOG FLY BREEDING IN PEANUT LITTER
By W. E. Dove and S. W. Simmons,
~Division of Insects Affecting Man nd Animals
Near the coasts of northwestern Florida and in bordering portions of
Alabama and Georgia the name "dog fly" is used for the stable fly (Stomoxy
alitrans (L.)),* a pest of livestock which occurs in all temperate regions
of the world. Because this fly is a painful biter of man and other warm-
blooded animals and emerges in outbreak numbers during different warm
periods of the year from peanut litter left in the fields, it is important
to control such breeding places so that outbreaks of the pest may be avoided.
In order to control the pest successfully and to determine the degree
of control, a good understanding is needed of (1) how dog flies develop,
(2) how to recognize favorable breeding places, (3) how to eliminate poten-
tial breeding places before they become infested, and (4) how to reduce
breeding places if the peanut litter is allowed to become infested.
How Dog Flies Develop
Dog flies lay elongated, creamy-white eggs, more or less scattered.
on moist places of fermenting vegetation. Within 1 to 3 days the eggs
hatch, and under the most favorable conditions the larvae become fully
developed within about 7 days. The larvae may require 30 days or even
longer for development if the food is unfavorable or the temperatures are
low. When full-grown, they are about four-fifths of an inch in length,
and in fermenting media they move rapidly and can quickly conceal them-
selves. When fully developed the larvae become shorter, and the outer
surface hardens and gradually assumes a dark-brown color. This is known as
the pupa, or restng stage, and it may last from 5 to 20 days or longer
before the flyemerges iand pushes its way to the surface. The complete
deelopment -from deposition of the egg to emergence of the fly may take
place in a period as short as4 days, but it usually ranges from 21 to 25
*1 Bishopp, F. C. The Stable Fly. U. S. Dept. Agr., Farmers'
... Bulletin No. 1097. (Revised October 1939.)
days and may extend to 76 days. Longer periods undoubtedly occur in un-
protected places during the winter months. In laboratory cages the adult
flies have been kept alive for 47 days, and often they fed upon blood on
two occasions each day. On an average the female flies deposited fertile
eggs when they were 11 days old.
How to Recognize Favorable Breeding Places
When vegetation cured for hay becomes wet from rainfall a mild
fermentation sets in which is particularly attractive to dog flies desiring
to lay eggs. As the fermentation progresses, the vegetation becomes more
suitable as food for development of the larvae, and the moisture assists
the pupae in producing adult flies. With these natural food requirements
for dog fly development in mind, an investigation was made of an outbreak
of flies in northwestern Florida and southern Alabama during the second
week of December 1940.
In Walton County, Fla., the livestock were suffering severely from
dog fly bites and some young pigs had died from the attacks. An examination
of litter in the peanut fields revealed mass infestations of dog fly larvae
and pupae in the exact locations where hcusands of the flies were emerging.
Similarly, in Geneva County, Ala., where cattle had as many as 300 dog flies
per animal and hogs squealed incessantly and stamped their feet because of
the biting flies, examinations of peanut litter in the fields again revealed
tremendous numbers of dog fly larvae and pupae. Since the outbreak appeared
to be of a rather general nature, examinations were made at different places
throughout the principal peanut-growing section. It was learned that dog
fly breeding was present in every pile of litter examined in 10 counties
of northwestern Florida which involved about 70,000 harvested acres, in
9 southern counties of Alabama having about 300,000 harvested acres, and
to a limited extent in southwestern Georgia where 33 principal peanut coun-
ties having approximately 630,000 harvested acres had received practically
no rainfall. From the best data available it appeared that approximately
1,000,000 acres of peanuts were harvested in the principal area and that
a considerable number of acres were harvested in other widespread areas of
these three States. Allowing 10 acres for each pile of litter in the most
important peanut-growing section, it is estimated that there are about 37,000
piles of infested litter in western Florida and southern Alabama and that
similar breeding could occur in approximately 63,000 piles of litter located
in 33 adjoining counties of southern Georgia.
Each breeding place examined in the fields represented the location
where peanuts were picked from about 10 harvested acres and where the peanut
vines were baled for hay. The piles of litter consisted of leaves, broken
stems, and peanuts, usually averaged about 25 to 30 feet in diameter, and
ranged from 1 inch in depth on the edges to 3 feet or even 4 feet in depth
in the center. A screened cage, 6 feet by 6 feet, placed over a portion of
one of these piles recovered approximately 10,000 newly emerged dog flies
within a period of 48 hours. An examination of the wet litter almost com-
pletely broken down by decay invariably revealed full-grown larvae and
pupae. When portions of piles in early stages of fermentation were examined,
only eggs and active larvae were found. Since about I week is required for
larvae to develop and pupate, a casual examination of the litter is of
assistance in anticipating the stage of development contained in the litter.
Portions of piles of litter containing bright, well-cured leaves
and stems are capable of developing infestations at some future time.
Such material may not become wet until several months after harvest, then
promptly undergo fermentation and produce large numbers of flies.
In addition to those in peanut litter, dog flies can be found breed-
ing in straw mixed with manure, either inside or outside of barns, as well
as in any piles of green or cured grasses2 and refuse from vegetable packing
houses which are allowed to become wet and ferment in the presence of the
How to Eliminate Potential Breeding Places
Before They Become Infested
Since infestations of dog fly larvae and pupae may be found through-
out piles of wet fermenting peanut litter, with the possible exception of
very deep portions, the entire pile should be considered as a potential
breeder of dangerous numbers of dog flies. It is recommended:
(1) That all peanut litter suitable for feed be baled with the hay
or hauled to shelter immediately after harvest and stored so that it will
not get wet.
(2) That all peanut litter left in the fields be scattered at the
location of the piles and plowed under immediately after harvest.
(3) That peanut litter, or hay, and manure scattered around feed
troughs be hauled to the field each week and thinly scattered so that it
will dry completely.
(4) Soil erosion on the plowed areas may be avoided by choosing
level tracts upon which to scatter the material, or by planting appropriate
2 Simmons, S. W., and Dove, W. E. Control of Dog Fly Breeding in
Beach Deposits of Marine Grasses. U. S. Dept. Agr., Bur. Ent. and Plant
Quar., E-541 (multigraphed). June 1941.
UNIVERSITY OF FLORIDA
3 1262 09230 3923
How to Reduce Breeding if the Peanut Litter
Is Allowed to Become Infested
It is more satisfactory to scatter the litter thinly immediately
after harvest, before it has had an opportunity to become infested with
dog fly larvae and pupae than to wait until later. If this is not accom-
plished, it is important to reduce breeding to the lowest degree. Remember
that any pile of peanut litter remaining in a field without attention can
easily produce from 75,000 to 100,000 dog flies.
By the time the litter becomes infested it is difficult to scatter
the infested portions with a pitch fork because they are partly decayed and
do not hold together. At that time much of the infested material may be
mixed with soil as a result of "rooting" by hogs and it is absolutely
necessary to use a good shovel. All the soil mixed with infested litter
should be loaded on a wagon or manure spreader and scattered. If the mate-
rial is distributed thinly over the land and allowed to dry, larvae not-yet
sufficiently developed to transform into flies will be destroyed, and many
of the pupae will die from exposure to low temperatures in the winter.
Numbers of such pupae will produce flies when exposed on the surface of the
soil, but the emergence will take place during a warm period of winter
when there is little opportunity for the flies to survive the colder weather
that follows. It is not recommended that the infested material be plowed
under immediately, because this would simply delay the emergence of dog
flies until later, when the soil has become warm and when the newly emerged
adults would easily push through several inches of sandy soil.
It is recommended that manure from stables and piles of peanut hay
mixed with manure outside of barns be scattered each week of the fly season.
This will prevent the development of both dog flies and house flies.