Fly Predators

Fly Predator Life-CycleFly predators are small parasitic wasps that attack and kill filth flies in their immature pupal stage. Very effective because they kill the pest before it can mature into a flying adult. Female fly killers deposit their eggs inside the pest pupae and once hatched, the tiny larvae consumes the contents. Parasitic wasps are very aggressive and have a strong natural incentive to actively seek out fly pupae in order to reproduce. They will NOT bother people, pets, or animals.

Fly predators are shipped still developing inside the host, packed in a paper bag, and mixed with wood shavings for protection. Depending on the temperature during shipment, parasites will start hatching 1-4 days after arrival. Warmer temperatures will make them hatch faster, while cooler temperatures will slow the hatch. Do not store at temperatures lower than 60°F.

Start releases when some of the fly predators have hatched in the bag. Keep the closed bag in a warm place (around 70°F.) out of the sun until you notice some movement inside. Release parasitic wasps as close as possible to the breeding sites where fly larvae activity can be seen or is suspected. Do not release all in one spot and try to cover the entire fly breeding site. These biological fly killers will move around in a 100 yard radius in search of pest pupae and will even burrow into the breeding site. Simply sprinkle the contents out of the bag. If direct sun is a problem, covering the pupae with dirt or organic matter is advised.

Have a fly problem? We recommend fly parasites for effective, long-term pest control. A bag of 2,000 — enough to protect 4 large animals — costs only $15.50 and includes shipping!

For best results, start releasing before flies become a problem. Release rates, as with any beneficial insect, depend on several factors. The following guidelines have been successfully tested under normal pest conditions:

large animals (horse, cow, etc.) – 500 per animal

medium animals (sheep, goat, etc.) – 250 per animal

small animals (birds, rabbits, etc.) – 5 per animal

manure & compost piles – 5 per cubic foot

Tip: It’s best to make releases throughout the entire pest season for the following reasons:

1.) Flies have a much shorter life-cycle than the parasites.

2.) Flies produce more eggs in a shorter period of time.

3.) Releasing small amounts of parasites weekly, every other week, or even monthly has proven to be more effective than one large release.

Note: Fly predators will not attack adult flies, thus care must be taken to keep the existing population as low as possible (see How Far Can House Flies Fly?). We recommend using at least one fly trap and perhaps even baits. If a quick-knockdown is required, avoid spraying near the breeding sites where beneficial insects are active. It will do more harm than good.

Along with beneficial insects, you should employ a combination of measures to achieve the greatest reduction of flies: cultural control (sanitation), manure management (disposal), and water management (fly larvae need a moist environment to grow).

Related Sites:

Livestock & Livestock Building Pest Management – Ohio State University

Parasites for filth fly control on dairies – University of California Agriculture

Biological Control of Flies – University of Kentucky