BATON ROUGE, La. — A group of researchers led by LSU AgCenter entomologist Lane Foil has received a $90,000 grant from the U.S. Department of Agriculture to develop improved methods for controlling stable flies while reducing the amount of pesticides used to control this livestock pest.
The U.S. beef industry loses more than $2 billion each year because of insects, and the stable fly is considered the second-most important cattle pest, Foil says. Many Louisiana cattle producers have identified the stable fly as one of their primary insect problems.
Historically a problem with confined animals, the stable fly has emerged as a significant cattle pest in Louisiana because of changes in the way producers care for their livestock.
Foil says Louisiana cattle producers manage primarily cow/calf operations — with their herds in pastures that aren't usually an ideal habitat for stable flies. But times have changed.
"In the past 15 to 20 years, Louisiana producers have increased the production and feeding of hay, primarily using large, round bales," Foil says. "The combination of spilled hay, manure and water creates a high-moisture, muddy habitat that produces thousands of flies each day."
During peak season, cattle suffer from "explosive populations" of stable flies, Foil says. The insects — daytime feeders that swarm around the cattle — force the animals to bunch up together and refrain from feeding.
The primary time of infestation in Louisiana is late winter through early spring — the time when producers are most likely to feed hay because pasture grasses aren't growing. This is also the time of year when most calves are born, creating an additional stress on cattle herds, Foil says.
Foil and his colleagues will be testing a two-pronged attack on stable flies. The first step will be to release a particular species of nematode — a small worm that the researchers expect will feed on the stable fly larvae — while the second step includes treated targets to draw the flies to pesticides.
"We looked at a number of different avenues to control the breeding habitat," Foil says, explaining that chemicals are ineffective on the fly eggs because the eggs are buried in a muddy morass the chemicals can't penetrate.
"We think we can get them into the habitats," Foil says of the nematodes, which were brought in from Arkansas where they're being used in studies to control houseflies. "We know they will work in certain situations."
Foil says the nematodes are important, because chemicals alone won't do the job.
"Entomologists know you can't control just adults," Foil says. "You need to control the breeding habitats, too."
The visual target the researchers will use to control adult flies came out of studies to control tsetse flies in Africa, where scientists have used large pieces of cotton poplin cloth laced with insecticides. The insects are attracted to the cloth, where they pick up the insecticide when they land.
"One problem with controlling adult flies is that although they bite cattle, they rarely stay on an animal as long as five minutes," Foil says. "Treating animals with insecticides doesn't work."
Foil explains that to survive, stable flies require a daily "blood meal." They must feed on animal blood. Their preference is cattle, although they'll bite other animals or people if cattle aren't around.
"People hardly ever get bitten — unless the flies are hungry," Foil says.
Early experiments with the cloth target show more than 1,000 stable flies land on a target in a single hour. The researchers will spend the next two years working with cloth colors and insecticides to determine the most effective combination to control the insects.
"Preliminary results indicate the use of treated targets will be a viable strategy for adult stable fly control," Foil says.
"Data indicate that one of our current targets could have a potential to eliminate over 10,000 adult stable flies per day," he adds. "If we use two targets to protect 20 cows, we would be using 4 percent of the insecticide currently recommended as a single spray treatment for stable fly control."
Foil said he hopes the project proves successful and producers adopt the control measures.
"If the techniques we propose are used rather than treating cattle with pyrethroid sprays every 14 days during a three-month stable fly season, we could see nearly a 99 percent reduction in the amount of insecticide used," he said.
In addition to Foil, other researchers working on the two-year grant project are Jerry Hogsette with the U.S. Department of Agriculture's Agricultural Research Service in Gainesville, Fla., and Allen Szalanski with the University of Arkansas in Fayetteville, Ark.
Rick Bogren writes for the LSU AgCenter.