House fly control

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Leaflet No. 18

U.S. DEPARTMENT OF AGRICULTURE

HOUSE FLY CONTROL

By F. C. BrsHopp, assistant chief in charge of research, and L. S. Henderson,
entomologist, Division of Insects Affecting Man and Animals, Bureau of Ento-
mology and Plant Quarantine, Agricultural Research Administration

OUSE FLIES carry disease and filth. All sorts of germs can be found
on their hairy legs and feet, and in their digestive tracts. They
spread dysentery and typhoid, as well as intestinal worms. They are
also very annoying to people and livestock.
We can control these pests by preventing them from breeding.
Those that develop in spite of our efforts to prevent them, we must
destroy or exclude from our homes.

How Flies Live

It is easier to control house flies if we know how they live. House
flies lay their eggs in manure and fermenting vegetable matter. They
feed upon and breed freely in the moist excrement of horses, hogs,
chickens, and man. Garbage, fermenting farm wastes, and cattle
manure, especially if mixed with straw, are also favorable breeding
places. From 2 to 21 egg masses, each containing about 130 eggs, may
be deposited by one female during a lifetime of 2 to 12 weeks.

The white eggs, which are‘laid in cracks in the manure, hatch in
10 to 24 hours. The larvae, or maggots, complete their growth in 3
to 7 days. They are then creamy white and about one-half inch long.
They crawl to the edges of the manure pile; some may burrow into
the soil near the breeding material, and the rest seek other suitable
places in which to change to adult flies. While this change is taking
place, the insects are in the pupal, or resting, stage. The barrel-shaped
pupae are yellowish at first and dark brown later. In warm weather
the pupal stage lasts from 3 to 6 days, but in cold weather it may
last many weeks. When this change is completed, the adult flies push
open the end of the pupal case, work their way to the surface, spread
their wings, and are soon ready to fly away. They mate and the
females are ready to lay eggs in 21% to 20 days after emergence.

Prevent Flies From Breeding

The first step in the control of house flies is to keep them from
breeding. There are several ways to do this. Choose the methods
that best fit your local conditions and needs.

Issued May 1939
Revised April 1950

Scatter Manure on Fields

Remove manure and other farm waste every day and scatter it on
fields wherever practical. A manure spreader is useful. Spread the
material rather thin, so that any fly eggs or young maggots present
will be killed by heat, cold, or drying.

Store Manure in Pits or Ricks

Where it is impractical to scatter manure every day, store it in
fly-tight boxes or pits. They should be made preferably of concrete.
Put the manure into the container promptly, and keep the doors closed
when not in use. Place fly traps over holes in the top of the pit.

For storing large quantities of manure, pile the loads in rectangular
stacks, or ricks. Make these ricks wide enough for the wagon or truck
to drive over the top to dump and pack down the manure as each
load is brought in. They may be as long as is necessary to hold al!

House fly adult (enlarged). House fly larvae (greatly enlarged).

the manure. Make the sides as nearly vertical as possible and pack
them with a shovel. If possible, make a concrete base for the rick;
dig a ditch around it, and pour crude oil in the ditch. The heat
venerated in the manure will kill many maggots and drive the res
to the surface. Many will drop into the ditch and be killed.

Treat Manure With Chemicals

Another way to prevent flies from breeding in manure is to treat it
with chemicals to kill the eggs and maggots. Borax is effective for
this purpose. Dissolve 11 ounces in about 5 gallons of water for each
8 bushels of manure. Sprinkle the solution on the manure after it has
been piled. Manure treated at this rate can later be used for fertilizer
if less than 15 tons per acre is appled. Heavier applications may
injure some crops.

A mixture of two common fertilizers, calcium cyanamide and super-
phosphate, in equal parts will also greatly reduce fly breeding in
manure. Scatter this mixture dry over the manure at the rate of 1
pound to each bushel, and then sprinkle thoroughly with water.

§82196°—50 3

If manure is accumulating rapidly and is piled compactly, you will
need to treat only the surface of the pile, as flies breed only in that part.

Construct and Care for Stables Properly

To aid in controlling flies on the farm, construct stable floors of
concrete if possible. Pack dirt floors down hard, and occasionally
remove the loosened manure-soaked surface dirt. Make plank floors
as tight as possible, and scatter a little borax along the cracks every 2
weeks. Clean floors of all types often. Keep the corners of feed
boxes and mangers clean, as flies often breed in such places.

Dispose of Sewage and Garbage

The danger of typhoid fever and other intestinal diseases can be
avoided by the proper disposal of human excreta. In large towns and
cities an adequate sanitary sewage system is generally provided, and
all the houses should be connected with it. In smaller towns and rural
communities sanitary privies,| from which flies are excluded, are a
necessity. Until open-box privies can be replaced, prevent fly breed-
ing in them by scattering over the excreta every 3 or 4 days enough
borax to make a white covering.

Kill Flies With Sprays

Despite every effort to prevent their breeding, some flies will de-
velop, especially on farms. To kill these flies, apply sprays in
places where they gather and rest—in barns or around houses and
where they get into houses or public buildings. Two types of fly
sprays are used. Space sprays give quick knock-down of flies and are
useful for obtaining immediate results. Residual sprays kill more
slowly but leave a deposit that will be effective for a long time.

Because insecticides are sold in various forms and with different
proportions of the active ingredient, it is important to read labels
carefully and mix or apply according to directions.

Precautions

Do not spray oil solutions near fires.

Avoid unnecessary or prolonged exposure of the skin to insecticides.
Avoid breathing large amounts of the mist over an extended period.
Do not contaminate foods, dishes, or utensils with insecticides.

Space Sprays and Aerosols

Flies on the wing can be killed with space sprays—insecticides
atomized into the air to form a floating mist of particles. Space
sprays are most effective indoors. Fill the air with the mist and keep
the room closed for half an hour. Use a good hand or electric sprayer.

For several years most fly sprays have consisted of pyrethrum ex-
tract dissolved in deodorized kerosene. These sprays are satisfactory

* Methods of constructing such privies and modern sewage-disposal systems are
described in Farmers’ Bulletin 1950, Sewage and Garbage Disposal on the Farm.

4

for general household use, because they give quick knock-down, are
practically nonpoisonous to man and pets, and are not likely to dama ge
furniture, draperies, or clothing. Pyrethrum sprays now contain
piperonyl butoxide, n-Propyl Isome, sesame oil, or some other chemical
that increases their effectiveness.

Several organic thiocyanates, which are synthetic chemicals, can
also be used in space sprays. Sometimes these materials are combined
with pyrethrum. DDT or methoxychlor is now included in some
pyrethrum or thiocyanate space sprays.

Some fly sprays are graded according to their effectiveness against
house flies. The grades are B, A, and AA, the last being the strongest.
Ungraded sprays may be of excellent quality, but when the consumer
buys graded sprays he can be sure of their quality.

Space sprays with particles of insecticide so fine that they remain
floating in the air for several minutes are called aerosols. They may
be produced by the use of a liquefied gas under pressure, as in the
aerosol bombs, or with mechanical or thermal atomizers. The
common killing agents in aerosols are pyrethrum and DDT or
methoxychlor.

Residual Sprays

The greatest benefit from some of the new insecticides is obtained
when they are applied as residual sprays to surfaces where flies crawl
or rest. When properly applied in the right amount, some of them
remain effective for several weeks or months. The flies are killed
simply by their feet coming in contact with the sprayed surface for
a short time. Residual sprays are important in the control of flies
in and around buildings.

During the first several years that DDT was used, one application
of a residual spray killed all flies that came in contact with the treated
surface at any time during an entire season. Recently flies in many
areas have developed a marked resistance to DDT. These flies may
also be more difficult to control with some of the insecticides now used
as substitutes for DDT.

Apply residual sprays with hand or power sprayers operating at
low pressures (less than 100 pounds per square inch). High pressures
cause waste, as the spray is broken up too fine and rebounds to create
a mist. The object is to moisten the surface without causing run-off.
You can best do this by using a nozzle that will give a flat or “fan- -type
spray. Hold the nozzle about 18 inches from the surface and move
it up and down the wall so as to moisten the surface evenly. One to
two gallons will cover about 1,000 square feet.

Around Homes

Outside the house—Apply residual sprays to screens, porches, gar-
bage cans, and other places outside the house where flies gather. For
this purpose use DDT, methoxychlor, lindane, or chlordane.

You can generally obtain DDT and methoxychlor as wettable pow-
ders or as emulsion concentrates at different concentrations. Both
materials are recommended for use around homes at 2.5 percent
strength for suspension sprays and 5 percent for emulsion sprays. To
prepare a 2.5-percent suspension add 2 pounds of a 50-percent wettable
powder to 5 gallons of water. One gallon of a 25-percent emulsion
concentrate to 4 gallons of water will make a 5-percent emulsion.

Chlordane is available as a 2-percent solution in oil, which should
be used as purchased. Emulsion concentrates containing 50 percent
of this chemical are also on the market. Make a 2-percent spray by
mixing 1 pint of this concentrate with 3 gallons of water.

Lindane is being sold as a 25- _percent wettable powder and as an
emulsion concentrate containing 20 to 25 percent of the insecticide.
The finished spray should contain 0.3 to 0.5 percent of lindane. The
approximate dilutions are given in the accompanying table.

Duiutions for lindane sprays

For 0.3-percent For 0.5-percent
lindane spray lindane spray
Lindane formulation |
Formula- | calens Formula- Catone
tion : tion :
water | water
2.5-percent wettable powder_ --_| aS pounds-_ 4 100 | 16 pounds__ 100
% pound ___| 5 | % pound_-___ 3%
20-percent emulsion concentrate_| 1 gallon____| 65144) 1 gallon____ 39
Limba sees SPAR ibereyuayec een A%
25-percent emulsion concentrate_| 1 gallon__ 82%] 1 gallon____ AG
1 pints se 10%! 1 pint______ 6%
| |

Inside the house.—lf a house is weli screened and residual insecti-
cides are used outside where flies concentrate, residual treatments in-
side the house are usually not necessary. The flies that do enter may
best be killed with space sprays or aerosols.

DDT and methoxychlor are the only residual insecticides now rec-
ommended for fly control within the house. A 5-percent solution
of either material in refined kerosene is most suitable. You can apply
it with an ordinary household sprayer or paint brush. Use enough
to moisten the surface thoroughly, but not so much that the spray runs
off. On most surfaces 1 quart of solution will cover about 250 square
feet. Treat the flies’ favorite resting places, such as screens, hanging
_light fixtures and drop cords, edges of arches, beams, door and window
frames, and other projections or uneven places on the ceiling and
walls. It is not usually necessary to treat the entire walls and ceiling.

In Dairy Barns and Milk Rooms

Residual sprays applied in dairy barns and milk rooms protect the
livestock from annoyance by flies, help protect dairy products from
insects and the germs they carry, and indirectly reduce the number of
flies in the house and in other buildings.

Lindane and methoxychlor sprays are recommended for use inside
dairy barns and milk rooms. You should apply them at the strengths
recommended for treating around the home. DDT and chlordane are
not recommended for such use. For treating barns, power sprayers
are most satisfactory; compressed air or knapsack sprayers may be
used.

6

Milk rooms should be well screened. If flies elsewhere on the
farm are satisfactorily controlled, the space sprays may be the only
treatments necessary to kill the flies that occasionally enter milk
rooms. °

Spraying a barn door with a power sprayer.

In Other Farm Buildings

Because flies also congregate in other farm buildings, such as beet-
cattle and calf barns, stables, poultry houses, and hog pens, it is 1m-
portant that you treat these buildings. Spray them with DDT,
methoxychlor, chlordane, or lindane in the manner described for their
use around the home.

Large numbers of house flies can be caught in properly built traps
set in the right places.

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A trap 18 inches in diameter and 24 inches high, with the sides and
top of screen and a screen cone inside reaching from the bottom
nearly to the top, is most effective. The legs should be about 1 inch
long. The frame may be made of barrel hoops and laths or of metal.

Place the bait beneath the trap in a shallow pan about 4 inches
smaller in diameter than the base of the cone and 1 inch deep. Use
any substance attractive to the house fly as bait. Blackstrap molasses
diluted with three times as much water makes good bait. Milk and
fruit waste are also suitable.

Set traps where flies naturally gather—usually on the sunny side
of a building and out of the wind. Keep the bait pan well filled and
wash it out occasionally. When the flies become piled more than a
fourth of the way up around the cone, empty the trap. If you turn
the trap upside down before opening it, you can shake the dead flies
out without letting many of the live ones get away.

The number of traps required depends on the size of the premises
and the abundance of flies. On a city lot 1 trap is usually sufficient ;
on a farm from 3 to 10 traps may be needed.

Catch Flies in Traps ”

Destroy Flies by Various Means

Electrocuting devices that destroy flies have been developed. AlI-
though such devices cost much more than conical traps, they require
less attention.

Flypapers, fly poisons, and swatters are useful for destroying occa-
sional flies in homes or food-handling establishments. The safest
and most effective poison consists of commercial formalin, 3 table-
spoonfuls to 1 pint of milk or water, and a little brown sugar. Put
some of this poison solution in a small glass jar, place a saucer hold-
ing blotting paper upside down on top “of the jar, invert, and insert
a piece of matchstick under the edge of the els

Exclude Flies With Screens

After you have prevented fly breeding by every method known and
killed or destroyed as many flies as possible, there will still be flies.
Foods in public places, as well as in homes, should be protected.
Screens are indispensable in places where foods are kept and are essen-
tial for protection from flies in homes and many other places. Fit
screens well and make screen doors open outward. In humid climates
screens of copper, bronze, plastic, or one of the rust-resisting alloys
are recommended; in dry regions galvanized or painted ones are a
isfactory. Screens with 14 meshes to the inch will keep out |
flies, but 16- mesh screens will exclude other insects oS ae ge
ees Sen a

* More details on the construction and operation of tr aps are sive en in Farmers’
Bulletin 734, Flytraps and Their Operation. '

U.S. GOVERNMENT PRINTING OFFICE: 1950 Bis.

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