Biological fly control methods are those which enhance and preserve naturally occurring populations of predators and parasites of flies.
A diverse heterogenous fauna of arthropods develops in production systems where manure is allowed to accumulate for prolonged periods of time.
Among these are species of mites and beetles which prey on fly eggs and larvae (mostly the small first-instar).
A number of species of hymenopterous parasites also visit the manure and lay eggs in fly puparia. These parasites then develop inside the fly pupae, killing the flies as a result.
The maximum benefit from predators and parasites is achieved with dry manure. In very wet manure, predators cannot move about effectively to find and consume fly eggs and larvae.
Likewise, parasites also have to find the fly pupae, and can more easily penetrate dry manure to find and oviposit in the pupae.
Therefore, cultural practices designed to reduce fly breeding by manure drying, will at the same time encourage predators and parasites of the immature stages of the flies.
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