Livestock News

Biologically-Based Fly Management

House and stable flies are common insect pests affecting dairy and other livestock production. Biological control is one component of a complete management program for keeping these nuisance flies at low levels. The biological control component of an IPM program encourages farmers to conserve naturally occurring populations of predatory beetles, mites and parasitoids that attack flies by not applying insecticide directly to the manure. Populations of fly pupal parasitoids can also be enhanced by augmentative releases of several commercially-available species. For example, Muscidifurax raptor is a common species in dairies and Spalangia nigroaenea is common at feedlots. M. raptor is a versatile species attacking house and stable fly pupae inside barns as well as outside and it accounts for most of the naturally-occurring parasitism on dairy farms. These wasps kill the fly pupae both by parasitizing them and host feeding.

Be sure the parasitoid you release is the right one for your situation. The commonly-sold Nasonia species are inexpensive, but inappropriate for dairies and feedlots. Be aware that some parasitoid species are better suited for certain livestock than others, or may be adapted to certain climates. Also be aware that parasitism by the various species is greatly influenced by location, the type of confinement (dairy barn, feedlot, pasture), the proximity to other fly breeding sites, and sanitation levels.

Plan ahead for parasitoid releases. Start early, preferably by May and continue weekly until the middle of August in the northern states; start earlier and continue longer in southern areas. Parasitoids are generally sold as immatures in killed fly pupae. If they are shipped in cheesecloth bags, these bags can be stapled to posts or rafters near areas where fly breeding is a problem. Loose pupae can be sprinkled around in protected areas, but placing them in wire mesh containers attached to walls or posts will protect them from predation by birds and mice, and from being smashed.

Parasitoid release rates and schedules will differ for every farm, so adjustments must be made from recommendations to achieve effective and affordable control for each individual operation. In research trials on dairy farms in New York, weekly releases of either 200 parasitoids per milking cow or 1,000 parasitoids per calf provided effective control when included as part of an overall IPM program. If calves are housed in hutches, place about one heaping tablespoon of pupae (approximately 1000) in each hutch weekly.

Don't Waste Your Money on Fly Parasites Unless . . .

For biologically-based management programs to be successful, sanitation and manure management are essential. Although parasitoids can reduce fly populations, they don't work quickly and they may not destroy all of the flies. Removal of fly breeding sites, including manure, soiled animal bedding, spilled feed, and garbage, breaks the life cycle of the flies. Clean up these materials once or twice a week.

Spreading manure and manure-soiled bedding thinly (less than 2 inches) on fields promotes drying and dessication of fly eggs, maggots, and pupae, and may make them more accessable to predators.
Manure can be stacked for composting (keep the sides as vertical as possible to prevent spillage) and the high internal temperatures will kill maggots and pupae. Composting will be improved by turning the stack once or twice a month.
Calf hutches deserve particular attention. Make sure they are located in a well-drained area. Use coarse sawdust rather than straw for bedding to reduce fly breeding, and clean the hutches frequently to further reduce maggot numbers.
Keep open-trench silos well drained and free of material along the edges and the open end.
Clean up spilled feed, grain, and garbage regularly.

Traps can also help reduce adult fly populations when placed and used properly.

Related Publications

Integrated Management of Flies In and Around Dairy and Livestock Barns, by D.W. Watson, J.K. Waldron and D.A. Rutz. Cornell Cooperative Extension Dairy Mangement Fact Sheet : 102 DMFS 450.00. Available for $1.25 from Cornell Coop. Ext., IPM Program Office, NY State Agric. Exp. Station, Geneva, NY 14456.

How to Control House and Stable Flies Without Using Pesticides, by L.G. Pickens, E.T. Schmidtmann, and R.W. Miller. USDA-ARS Agriculture Information Bulletin 673. Copies of this publication may be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.

- Wes Watson, Cornell University and Gerald Greene, Southwest Kansas Research - Extension Center

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