Do Fly Predators Fit In Your Fly Control Program?

Stable Flies and House Flies are two of the more common species of flies that bother horses during the warm months, especially around barns and stables.  Since it is April 1 (no fooling!), warmer temperatures are almost here, so it is time to consider what the fly control program will consist of during the rest or 2019.

Most horse owners and barn managers incorporate several fly control tools into the program to achieve the best results.  One method is mechanical control – removing manure, old bedding, and other fly breeding areas from the stable or barn.  Often this material can be composted, which will destroy any eggs and larvae during the process of turning this material into a pretty good soil amendment for gardens and landscapes.  Another is using insecticides to eliminate flies in concentrated areas, barriers are used to prevent flies from landing on the horse, especially around the face and eyes. Other tools include feed-through products for larvae control, and fly traps.

One tool that doesn’t get much discussion is the use of fly predators on horse farms.  These predators are tiny wasps that do not sting people or animals, but instead search for fly larvae to lay their eggs in. The predator larvae hatch inside the fly larvae and feed on it, preventing that fly larvae from becoming and adult fly. This helps to break up the fly life cycle and reduces the fly pressure around the horses.

There are several species of fly predators, and they are fairly specific to the type of fly they will help control.  They work best on either house flies or stable flies.  Some of the more commonly found species of fly predators and the type of flies they control are:

·     Spalangia nigroaenea - attacks both house and stable flies. 

·     Muscidifurax raptor– attacks house flies.

·     Muscidifurax zararaptor – attacks house flies.

·     Spalangia nigra – attacks stable flies.

·     Spalangia cameroni – attacks stable flies

·     Spalangia endius  - attacks stable flies

There are other species that will attack horn flies and face flies, but house and stable flies tend to be the ones found in stables and barns where the fly predators are more effective and cost efficient.

To use the fly predators in a fly control program, identify “hot spots” around the barn, and distribute the predators near those according to recommended populations of predators for the number of horses present.  The fly predators will travel up to 80 yards to find manure that contains fly larvae to parasitize. However, the fly predator population will not keep up with fly numbers throughout the fly season, so monthly releases of the fly predators through the control season are recommended.

Take care when using fly control insecticides if using the fly predators.  Don’t spray near the areas where fly predators have been released as the insecticide will also kill the fly predators.  If using a feed-through fly control product, the fly predators may be better used around concentrations of grass clippings, old bedding, or old round bales left on the ground. House and stable flies will lay eggs in these materials, so if they are not handled properly, these materials can be a breeding ground for flies.

There is no magic treatment that will totally eliminate the fly problem, which is why an integrated control program using different methods is recommended.  Sanitation, barriers, mechanical controls, insecticides, and biological controls can be combined to provide wide-spectrum fly control. Perhaps fly predators can be an effective tool to help in the fly control battles this summer.