Cattle fly control

Flies can take a significant toll on cattle productivity.

The buzz on fly control is pretty simple—there are a lot of effective ways to limit flies on cattle.

Just as there’s more than one way to skin a cat, there’s a whole host of means to kill flies—ear tags, sprays, pour-ons, dust bags, oilers, larvicides.

The key, according to Kansas State University Extension Beef Specialist Karl Harborth, is to select the one that best fits your situation.

“The products are effective,” he explains, “but each of them have to be administered correctly in order to be effective. Dust bags, for example, work well but only if you can set up a situation that forces the cattle to use them. That’s the case for all of these products—they have to be used right if you want to be happy with the results.”

The evidence in favor of doing something to control flies is pretty compelling, Harborth notes. University studies indicate weight losses of 10 to 20 pounds for nursing calves and a 14 percent stocker cattle weight loss over a 120-day fly period, as well as assorted health problems.

“Losses are going to vary from year to year and from one situation to another but there certainly can be a pretty significant amount of money left on the table from not making an effort to control flies,” Harborth explains.

The animal scientist suggest that cattlemen start by cleaning up feeding sites which provide an ideal environment for fly populations to build.

“Flies can reproduce in the scattered manure patties out in the pasture but not nearly to the extent that they can in an area of old hay, mud and manure,” Harborth says. “That’s especially true in a wet spring like we’ve had—it’s the perfect place for populations to build.”

He acknowledges that flies have a fairly wide open range and notes that some producers will point out that, even if they do clean up feeding sites there is still the potential for flies from the neighbor’s place.

“That’s certainly true but I guess you have the choice of having flies that come in from neighboring areas or a high number of flies produced on your own place and flies that come in from the neighbors.”

The other primary means of prevention is the use of larvicides which prevent flies from developing. These feed-through insecticides pass through the animal and remain toxic to fly larvae development in the manure.

For those flies that are already hatched and on the prowl, the strategy switches over from prevention to protection.

Typically, there are two spikes in fly activity—early summer and then again in the fall when temperatures begin to drop and conditions are typically a little wetter.

Getting ear tags on about the time populations get heavy in early summer is very effective but Harborth is adamant about getting those tags out of the cattle ears at the end of fly season.

“If you don’t get them cut out, that reduced level of chemical remaining in the tag is going to allow some flies to become resistant to that particular active ingredient,” he points out. “That’s going to set you up for a more difficult situation in the future.”

Avoiding a tolerance buildup is the reason entomologists suggest rotating active ingredients and that doesn’t mean tag brands, Harborth cautions.

“You need to read the label and know what that active ingredient is and follow all label recommendations,” he adds.

Insecticide impregnated ear tags can provide good control of horn flies and may provide some reduction in face fly numbers. Horn fly resistance to synthetic pyrethroids, however, is an increasing problem.

Generally, producers select from pyrethroid or organophosphate tags. Whichever active ingredient they used last year, it’s suggested that they switch to the other this year, particularly if they notice diminishing control.

Tags are generally the most expensive single treatment but some can last up to five months. On a per head basis, sprays are the cheapest and offer a quick knock-down of fly numbers but residual control may only last a few weeks. Pour-on horn fly control insecticides generally last about six weeks.

The same advice on rotating ingredients applies to all types of control measures.

Cattlemen do have an additional insecticide type choice now. Elanco released Elector, the first new insecticide class available in 20 years. Elector is used as a spray or pour-on to control flies and lice.

Regardless of the product, Harborth’s advice is clear—use insecticides according to label, rotate active ingredients to prevent a buildup of tolerant populations and, in the case of tags, make sure they are removed at the end of the fly season.

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