Fly Control Article

Fly Control

by Eric W. Acosta, Biocontrol Network
Domestic Rabbit, Volume 25 Number 1
January-February 1997

The importance of effective fly control is often underestimated. Flies account for large annual losses in livestock producers' profits caused by both effects on animals such as weight loss and disease transmission, and by the expense of running an often inefficient fly control program.

In today's economy, no livestock producer can afford the losses flies cause, and he can no longer afford to treat fly control as a secondary issue. By the same token, a wisely planned and efficient fly control program affords him one of the best investments he can make.

The nectar and pollen of flowers are the primary foods of the majority of flies while many others depend on liquid organic matter, such as that from decomposing plant material or animal bodies.

The life cycles of flies include development from eggs to larvae (usually called maggots) to pupae to adults. A number of flies require a blood feeding to reproduce (such as stable flies), while others do not (houseflies).

The maggots are always legless and develop from thin whitish eggs, which have been laid in moist areas. Egg locations include decaying animal or vegetable matter. Hay, straw, and grass provide excellent locations especially when contaminated with manure or soaked with water. Once fully grown, the maggot develops a hardened, shiny dark brown outer case, characteristic of a pupae. This pupae is a dormant non-feeding stage which develops into an adult fly. The total life cycle can take from two weeks to several weeks, depending upon species, climate, and time of year.

The female house fly can lay as many as 1000 eggs in her lifetime. Fortunately nature accounts for 80-98% of fly control, in the way of natural predators and parasites, such as birds, reptiles, amphibians and insects that depend on various stages of the developing fly for food or reproduction. Even so, the prolific breeding of the fly can still lead to significant increases in the fly population on a daily basis under the right conditions.

Chemicals become less effective for fly control with repeated use as flies develop resistance to the chemicals with each generation. It took only a few years for flies to develop resistance to DDT after it was introduced. And, chemicals are becoming less and less available through Government restrictions as well as becoming more costly due to their dependence on the petroleum market. Augmentation of commercially produced fly predators and parasites such as beneficial nematodes and parasitic wasps have provided the livestock producer with economical and environmentally friendly alternatives.

Beneficial nematodes quickly and effectively help to eradicate the larval stage of the developing fly before it has a chance to become a menace to livestock and neighbors, which is an ever more important issue due to urbanization. Nematodes actively seek fly larvae upon which to feed and lay their eggs. Within 48 hours of this effective hunt and destroy operation, the host is dead and thousands of juvenile nematodes have been generated to continue with the mission.

Fly parasites, miniscule nocturnal wasps, burrow into the soil in search of the pupating larvae. The female wasp is ready to mate and oviposit immediately upon emergence from the host puparia. She deposits one to fifteen eggs, depending on species, into the living host. About two weeks later, fully developed adult parasites emerge to search out new hosts.

Fly traps help to control adult flies that manage to get past the first two control tactics, and flies migrating from outside areas. Controlling the adult population even a little increases the effectiveness of the other control measures. Fly traps come in many varieties, disposable traps with built in bait, reusable traps with bait that you replenish, and fly tapes, sometimes with fly pheromones as an attractant.

We have found that the use of these three controls effectively reduces filth breeding fly populations. Racetracks, such as Churchill Downs who have been using fly parasites for many years, no longer have fly problems. Potential users of biological fly control include pet owners, feedlots, dairies, breeding and training facilities, seaquariums, waste treatment plants and other places where flies are a problem. The program can be tailored to any type of operation.

For more information or assistance in developing your own fly control strategy, call Biocontrol Network at (615) 370-4301 or email Find additional information about Integrated Pest Management on the World Wide Web at

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Last Update: 23 June 98

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