New research suggests ranches, farmers and horse owners don't have to resort to the use of pesticides to control fly populations. Parasitic wasps work just as well, scientists say.

Filth flies, like house and stable flies, agitate horses and spread disease. When swarms get too large, some caretakers use pesticides and insecticides, but use of these chemicals can damage the environment. One way to curb pesticide use is to find suitable biological control agents to take their place.

In recent experiments funded by the U.S. Department of Agriculture and carried out by researchers at the University of Florida, parasitoids proved an effective fly-management tool.

Parasitic wasps lay eggs inside the fly's puparium, a shell filled with fly larva. When the wasps hatch, they eat the pupa.

Researchers tested two different types of parasitic wasp species and found that each has different manure preferences.

"In the lab, we found that the Muscidifurax species we tested preferred bovine manure, and the Spalangia species preferred equine manure, so there seems to be some sort of differentiation there, which could impact control on a farm," entomologist Erika Machtinger said in a press release.

In a new article published in the Journal of Integrated Pest Management, Machtinger and her colleagues offer advice on how to match the proper parasitoid with the resident fly species. They also provide information on how to safely and effectively release and manage wasps on a farm.

"This is a really good article, and very useful in pointing out some directions, and things that need to be addressed," said entomologist Lee Townsend, a researcher at the University of Kentucky who was not involved with the study. "The importance is high because people are looking for effective fly control. But they're also looking for sustainable ways to do that, particularly those that avoid excessive insecticide use."