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Triple Whammy Makes Nuisance Flies Flee the Coop

By Tara Weaver
January 21, 1999

A triple whammy of chemicals, lime and parasitic wasps could bring relief to people and farm animals plagued by nuisance house flies, Agricultural Research Service scientists report.

Pesticides alone aren’t enough to control these house flies, because the pests have developed resistance to cyromazine, a popular growth regulator added to feed that passes through the chicken and kills the fly larvae in the manure.

To find the most effective controls for the flies, ARS researcher Jerome A. Hogsette, in collaboration with scientists from the Institute of Agricultural Microbiology and Zoology in Buenos Aires, Argentina, conducted field tests in commercial poultry houses with cyromazine-resistant house flies.

The scientists found the best system for reducing house fly populations included limited-use of topically applied cyromazine, which is more concentrated than the feed additive; chemical pesticides; cultural control such as lime; and two parasitic wasps--Spalangia endius and Muscidifurax raptor.

The wasps were released at a rate of five of each species per hen per week after pesticide applications were stopped. The wasps are found worldwide, including the United States, and do not bite or sting people or animals. They only attack flies.

Combining these control practices reduced flies by 98 percent and resulted in a 3.5 percent cost savings compared to chemical treatments alone. Also, combined treatments resulted in a 2 to 3 percent labor savings a week.

Hogsette has also tested black dump flies in controlling house fly populations. A dump fly can kill up to 20 house fly larvae per day during its 5- to 7-day development. Black dump flies in animal manure can reduce house flies by almost 100 percent. The flies work best in moist conditions, whereas the wasps need a much drier environment, so the combination would prove highly effective.

Hogsette is with the Mosquito and Fly Research Unit of ARS’ Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Fla. ARS is the U.S. Department of Agriculture’s chief scientific research agency.

Scientific contact: Jerome A. Hogsette, Mosquito and Fly Research Unit, ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Fla., phone (352) 374-5912, fax (352) 374-5922,