Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/1997
Publication Date: N/A
Interpretive Summary: House flies, stable flies and other "filth flies" often are produced in large numbers on livestock and poultry farms. Fly outbreaks reduce farm profitability, cause public health and legal concerns for farmers, and are a source of sociological friction at the rural- urban interface. Farmers relied on chemical insecticides for fly control for many decades, but the flies are now resistant to most insecticides and there is increased pressure to reduce insecticide use near food crops and animals. In this article, scientists at the Center for Medical, Agricultural and Veterinary Entomology located in Gainesville, FL, report on a new species of nematode parasite of the fly that was recently discovered in Brazil. The nematode was found to be highly effective at parasitizing house fly larvae, even at the very low dose of 0.3 nematodes per fly larva. Infected flies laid no eggs and only lived half as long as uninfected flies. Nematodes survived in a free-living stage for about five days when they were applied to fly larval rearing medium. It is concluded that this species shows promise as a biocontrol agent for house flies.
Technical Abstract: House flies were highly susceptible to infection by the nematode Paraiotonchium muscadomesticae Coler and Nguyen when cups of rearing medium (250 cm2) and fly eggs (100 per cup) were inoculated in vitro with nematodes from infected adult flies. Infection levels ranged from 1.7 at 0.001 "infected fly equivalents" (IFE) to 100% at 10 IFE (300,000 nematodes). High larval and pupal mortality was observed among flies at the high dose. Infected flies of both sexes lived about half as long as uninfected flies. Examination of nematode age structure in infected flies revealed that mature gamogenetic females produce about 8 parthenogenetic females each regardless of nematode crowding levels. In contrast, production of new gamogenetic nematodes by parthenogenetic females was density-dependent, with average reproductive rates ranging from 1,627 progeny per parthenogenetic female at 8 females per host to 330 at 83 females per host. Infected flies contained 12,000-45,000 new gamogenetic nematodes 10-14 days after fly emergence. Male flies were as susceptible to infection as females. Gamogenetic nematodes required 24 h after deposition into fly larval rearing medium before they were capable of infecting new host larvae. Nematodes persisted in rearing medium for 3-5 d after deposition; no infections were observed at 7 and 10 d after deposition.