Bloodsucking flies can reduce cattle gains

By HEATHER SMITH THOMAS

When it comes to pesky livestock flies, the biggest rascal is the stable fly.

So Bill Clymer, Spalding Laboratories senior technical consultant for the California fly control business, is working hard to design an effective control program targeting these menaces.

It’s larvae can develop in decaying organic matter — old bedding, rotting hay, seaweed, etc. — when temperature and moisture conditions are right.

“In extremely hot weather with low humidity and no rain, flies are less a problem because it’s too hot and dry for reproduction. If sun is beating down on compost or manure, it can be too hot for larvae and pupae to develop,” he says.

Key Points

• Stable flies are the predominant cattle pest in all regions.

• Cattle bothered by flies don’t eat well; livestock performance can be reduced.

• Stable and horn flies easier to control than horse, deer or black flies.

Stable flies don’t breed in straight cow manure. They prefer decaying plant matter such as wet hay. “Texas A&M did a study and found that, if you don’t clean up, where you feed big bales is an ideal breeding ground. Researchers estimated that the area around one big round feeder produces more than a million stable flies,” says Clymer.

“On my own cattle operation, we unroll round bales in the pasture, but in corrals we put bales in feeders. One of the first things we do in spring is move the feeders and spread the wasted hay around with a front-end loader so it will dry out. Otherwise, this material stays wet almost all summer and provides breeding sites for stable flies.”

If you can keep flies from proliferating in spring, you may not have to do much for control during the hottest part of summer.

“But if you get a big rain, about 10 days afterward, you can expect a tremendous increase in emergence of stable flies,” he says.

Control measures

Clymer’s favorite comment is that there are three ways to control flies: sanitation, sanitation and sanitation.

“I also advise using parasitic wasps. They’re an environmentally friendly way to control flies, but they’re only one tool. Not any one thing will do it; we need an integrated program to control the flies migrating in,” explains Clymer.

Horse flies and deer flies are hard to control because they develop in wet areas that may be miles from your cattle. Horn flies are easier to control because they breed in cow manure, and adults spend most of their time on cattle. Black flies attack in swarms but are almost impossible to control because they breed in water. These small flies attack any animal and transmit a number of diseases.

Fly control tactics have changed in the past decades. “At first it was just a matter of when to start spraying and how long. Then because of pesticide resistance issues and concern for the environment, we’ve changed strategies,” says Clymer.

Most feedlots try to get rid of breeding sites, such as wet spots from leaking water troughs, and clean pens when there aren’t enough animals to trample the manure.

Get a pooper-scooper

“Pick up manure at least once a week. Under optimum conditions, flies will breed and hatch in seven to 10 days,” he says. Many feedyards also use parasitic wasps to help control fly development.

Other control measures include feed-trough larvicide products and feed-trough hormones that keep larvae from maturing.

“I advise ranchers to maximize sanitation, and consider using parasitic wasps. If you need to spray, just spot spray specific areas, since about 95% of fly breeding takes place in 5% of the area — where conditions are most ideal. But remember that using larvicide spray [applied to manure to kill immature flies] is a fast way to develop resistance issues. You also kill most of the beneficial insects,” he says.

Smith Thomas writes from Salmon, Idaho.

This article published in the April, 2010 edition of WESTERN FARMER-STOCKMAN.

All rights reserved. Copyright Farm Progress Cos. 2010.