Dr. Erika Machtinger, Assistant Professor of Veterinary Entomology at Pennsylvania State University recently reported on studies sponsored by the USPOULTRY Foundation (Project F077). The objectives were to develop biological control methodology representing potential benefits over the application of chemical pesticides based on both cost, environmental considerations and the development of resistance.
Dr. Machtinger evaluated an entomopathogenic fungus Beauveria bassiana that infects and destroys house flies. Dr. Machtinger also evaluated parasitic wasps (Spalalangia and Muscidifuraxspp.) and a beetle predator of fly larvae Carcinops pumilio.
Five new isolates of B. bassiana were identified that appear more virulent than previously evaluated strains. Virulence was determined by quantifying conidia on fly cadavers. After nine generations of selection, mean death time for flies was reduced by approximately three days to five days.
It is noted that parasitic wasps and an entomopathogenic fungus are commercially available but have minimal application in the industry. Experience with both parasitic wasps and beetles in relation to fly infestation shows that biological control of fly populations is favored by low moisture level in manure. With wet manure such as is encountered in high-rise houses with suboptimal pit ventilation and that allow seepage of groundwater, flies proliferate and parasitic wasps and beetles are overwhelmed. The converse is true, with relatively dry manure, fly breeding is inhibited and the parasitic wasps and beetles thrive and function.
As the industry has moved from high-rise houses to belt-manure systems, fly control is less critical provided that manure handling and drying are effective. Current observations suggest that flies are not a problem with aviary systems fitted with belt-manure removal coupled to appropriate manure storage and processing.
Operators of old high-rise houses must maintain adequate airflow to reduce the moisture content of manure. This must be coupled with judicious use of feed-through larvacides and tactical application of synthetic pyrethroids, provided that flies are susceptible to these compounds. In-house composting using specially designed equipment has proved beneficial in some applications especially when combined with acceptable ventilation rates.