Taylor and his colleagues developed a model to assess the economic impact of stable flies using four classes of production: dairy, cow/calf, pastured and range stocker, and animals on feed. They found that each year, stable flies cost the U.S. cattle industry more than $2.4 billion, making them the most damaging arthropod pest of U.S. cattle.

As their name implies, stable flies have historically been associated with stables and barnyards. But over the last 30 years, they have become a significant pest in pastures too. Research indicates the problem is partly due to the large bales of hay placed in fields as supplemental feed for cattle during the winter.

“The accumulation of wasted hay, manure, and urine at these feeding sites creates an ideal habitat in the pasture for stable fly larval development,” Taylor says.

“We identified hay-feeding sites as producing a lot of flies, but we wanted to know how the timing of the flies coming off the sites correlates with adult population levels.”

In Nebraska, stable fly populations peak twice a year — in mid-June to July and again in September or October. Scientists determined that the hay-feeding sites are the primary sources of flies in the June-July peak.

Stopping stable flies before they mature

Cleaning up infested sites has been the main stable fly control method for about 100 years, Taylor says. The problem is that hay-feeding sites are often in remote locations.

As for insecticide use, says Taylor, “This kind of habitat has an active microbial community that can break down most traditional insecticides very quickly. You might get a couple of days of control before the effectiveness wears off.”

The team found that using an insect growth regulator to interrupt the development of stable flies can be effective. In one study, Taylor used cyromazine to control immature stable flies. Cyromazine, a commercial product, has been used to control other species of flies, mainly in poultry production. It interferes with molting and inhibits proper development of the insect’s external skeleton.

“We wanted to develop a method where the producer could apply a single treatment and be done,” Taylor says.