The Buzz on Livestock Fly Control

cow

The biting stable fly is a painful nuisance to pastured cattle. Unfortunately, there’s nothing that can be done in pastures to reduce stable fly numbers except control the sites where they develop as maggots. The time to do that is before the insects have the chance to breed.


Ludek Zurek is a professor of veterinary entomology at Kansas State University. He says cattle feed around large round bales that stay in the same spot, and they end up defecating in that area. The wasted hay then mixes with the manure, becoming the perfect breeding ground for stable flies in the spring.  
He says the easiest solution is to move the feeder every time you put a new bale in it.

“Just pushing that feeder with a tractor or some equipment just a few feet away from the old site should do the job. The cattle start defecating into new spots, and the manure will not accumulate deep enough,” says Zurek. “It’s going to dry up in the spring, and that will prevent the larvae development of stable flies in the spring.”

Another alternative is to put hay feeders on a slope so the area can drain and dry out. 

If you can’t move the feeders and don’t have a slope, Zurek says you’ll have to do what you can in the spring.

“Try to rake that feeding site to spread the accumulated manure and hay into a thinner depth across a larger area. Again, it will dry up faster, and it won’t provide a habitat for stable fly larvae,” says Zurek.

While these blood-sucking insects don’t transfer any pathogens or parasites to the animals, there is an indirect economic effect. The bites are painful, and the herd might bunch for protection or stand in water to avoid the flies. They spend less time grazing, which, in turn, reduces weight gain. 

Keep Bugging Them

Bruce Brinkmeyer is the manager of farm hygiene products for Bayer Health Care. He says there are sprays and dusting powders that can be applied directly to the animals. Fly baits and residual sprays on surfaces work, too. Unfortunately, people don’t often think about the environment around the farm. 

“Where you’ve either been storing feed or you have old hay storage areas, these are the places where flies actually reproduce; it’s where larva and eggs are. These are the sources of flies,” says Brinkmeyer. “So eliminating or treating them with either powders or sprays, or just managing by cleaning them up will often reduce the fly pressure a lot.”

Flies love manure. It’s a favorite breeding ground, so another defense is to make it lethal for their offspring. Brinkmeyer says this is accomplished with feed-through products embedded with oral larvicides. 

Once consumed by the animal, the larvicide passes through the digestive system and into the manure where it kills maggots on contact after the eggs hatch. 

He says if you wait until you see flies to start a defense program, it’s already too late. “You really need to be concerned about the environmental areas as soon as the first spring thaw. That’s when eggs that have been laid over winter become active larva, and adult flies hatch surprisingly fast in the spring,” says Brinkmeyer. “Most of the time, you go to the store to buy something when it’s too late. The fly pressure’s gone beyond your threshold, and now you’re in a reactive mode all summer.”