| Managing
filth flies with parasitic wasps FIRST POSTED: October 2001 Biological control offers a safe and economical means of controlling fly populations at composting facilities. According to Rincon-Vitova Insectaries, a pioneer in the field of controlling filth flies through the use of beneficial insects, the species of flies that inhabit accumulations of animal manure and other breeding sites are attacked by over 200 kinds of predaceous and parasitic species of insects, spiders, and mites. Combinations of these beneficial insects are attracted to manure, destroying all life stages. Beetles and mites devour fly eggs and larva. The adult fly stage is partially controlled by natural disease. The pupa (or cocoon stage) also has one of the most important natural enemies of flies: small parasitic wasps. Parasitic wasps have a biological radar for finding fly pupae in manure and other fly breeding sites. Establishing good fly control in the first place is easier than attacking a population that has gotten out of control. Prolific and adaptable Muscidifurax raptorellus is mixed with hardy Spalangia cameroni in a ratio appropriate for the specific climate where beneficials are released. Typically, fly parasites are released when flies appear in the spring. By establishing parasites early, they multiply their numbers to keep up with fly breeding. You won’t see these tiny wasps, just the results as they work at night, hopping and burrowing in accumulated manure and waste. HOW FLY PARASITES WORK
Parasitic wasps lay their eggs inside fly pupae and the developing flies provide food from within for the young wasps. In addition, adult parasites "host feed" by drawing fluid from fly pupae, and thus prevent the fly from fully developing.
They are very effective against the housefly, biting stable flies, garbage flies, and the lesser housefly, which comprise 95 percent of the flies in manure accumulations. They also parasitize the other 5 percent of flies, such as horn flies, flesh flies, face flies and false stable flies, but control is less complete on those flies which complete their life cycle widely dispersed in the pasture.
The parasitic wasps only attack flies and will not bite, sting, swarm or bother anything else. They are nocturnal and are rarely seen during the day. Fly parasites operate to a depth of 8 inches in manure, homing in with their biological radar on fly larvae that are about to pupate.
Fly parasites complete a generation every 3 weeks, (from parasitism of the fly pupa to emergence of the adult) yielding a steady reproduction of parasites. The adult wasp lives about 10 days. The parasite populations increase geometrically and reductions in flies can be expected in 4 to 6 weeks. They will eventually kill almost every fly breeding at your location.
Flies still can be migrating in, however. Biological control works best if the whole neighborhood uses biological controls.
Bait trapping of adult flies is recommended to accompany fly parasite releases. Some chemicals or nonpoisonous materials are useful when they are formulated into sugar baits and fed to the adult flies. Bait traps can be economically and safely used without interfering with biological controls. (Use chemicals in moderation to prevent development of resistance to these controls. Pesticides also harm beneficial populations.)
Good pile management can also reduce fly populations. Dry manure does not breed flies. The interface between wet and dry manure that has a moisture content of 50 to 80 percent is where fly breeding occurs. This is also where the fly parasites work best. Thanks to Rincon-Vitova Insectaries Inc. for permission to use the information, artwork, and photographs in this article. To read the complete article and find out more about products for fly control, visit the Rincon-Vitova website at www.rinconvitova.com/flycontrol.htm. Click the link to read the "Fly Control Bulletin." |
Fly traps
and good management helps