Horticulture

Fly Management on the Farm – Know your Enemy!

In order to effectively manage and control fly pests, it is important to understand the breeding habits and life cycles of the key fly pest species. With this knowledge, you can create a specific “pest fly management” strategy. Adults are attracted to practically all types of organic matter, especially animal feed and manure, broken eggs, dead animals, etc.

An adult fly may live 30 days and a female can lay up to 900 eggs, usually laid in clusters. The larvae (maggots) use the moist, organic matter as food. After completing their development, they crawl to a drier area to pupate. The pupal stage is a resting and development stage in which each larva develops into an adult fly. The entire life cycle—from adult fly, to eggs, to larvae, to adult flies, to more eggs—takes only 7-10 days in hot weather.

Know their enemies!

Anywhere manure accumulates and stays reasonably dry, there will be an abundance of mites and beetles that prey on all fly stages and use them for their own reproduction. Dry manure means a more active and effective population of natural predators and parasites. Any cultural method undertaken to manage manure and biological methods implemented to kill flies are therefore complementary. Cultural controls used to reduce their ability to breed can include:

  • Stopping water leaks promptly: check the water supply daily for leaks, cracks, clogged lines, etc.
  • Managing feed storage areas: keep feed cleaned up around silos and feed bins
  • Maintaining adequate ventilation: air flow through areas where manure collects is critical to maintaining dry manure. Flies don’t like dry manure, therefore dry manure means less fly breeding.

Letting nature take its course would be acceptable under most natural conditions. However, high animal density in poultry, dairy, feedlot and farming operations produce large amounts of animal waste in short periods on relatively small areas. Fly populations can be correspondingly great. Therefore, it is necessary to supplement natural populations of predators and parasites with commercially produced fly parasites to increase the number of flies that are killed.

Enter—Fly Parasites

The most important natural enemy of flies are fly parasites called parasitic wasps. These tiny insects are completely safe to humans and animals. Frequent releases of fly parasites will reduce (and sometimes almost eliminate) fly populations. The adult fly parasite searches fly breeding areas for fly pupae. Once found, the fly parasite drills a hole through the armoured puparia and lays an egg on the protected fly pupa. The parasite egg hatches and the immature wasp eats and kills the developing pupa. After feeding on the dead fly, a new adult fly parasite emerges from the fly puparia in about 2-3 weeks. The new parasites then search out and kill more fly pupae. Each female fly parasite will kill about 100 fly pupae in its lifetime.

In summary, an adult female fly can lay up to 900 eggs within a week; an adult female fly parasite can lay up to 100 eggs in 2-3 weeks. This is why it is important to start your fly control program early, before the fly population explodes, otherwise you’re continually behind the eight ball and playing catch-up, which rarely works.

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