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Controlling cattle pests vital

Left untreated, pests can cause significant loss in production

Integrated pest management concepts that are commonplace for controlling crop pests also apply to controlling livestock pests, North Dakota State University Extension livestock and pest management specialists say.

Those key concepts for controlling pests effectively are using the right type of control at the right time for the right duration.

“Many livestock producers apply pest control prior to pasture turnout, which may be optimal for control of some pests but not others,” says Miranda Meehan, NDSU Extension livestock environmental stewardship specialist.

In a recent survey NDSU Extension conducted, producers reported that face and horn flies were the most common and most treated pest on their operations.

“Left untreated, these pests can cause significant loss in production,” says Gerald Stokka, NDSU Extension veterinarian and livestock stewardship specialist.

Horn flies are greyish and look like small houseflies. Horn flies are biting flies; they spend most of their time on cattle clustered on the animals’ head, shoulders and back. Horn flies also can be found on the cattle’s belly during warm weather.

These bloodsucking flies feed up to 30 times per day. This constant biting causes pain and stress, and can reduce weight gains by as much as 20 pounds. When fly counts reach 200 flies per animal, the “economic threshold” has been reached and animals will have significant weight loss.

The life cycle of a horn fly ranges from 10 to 20 days, depending on weather conditions. Populations typically peak in midsummer and early fall.

Face flies look like large, dark-coloured houseflies. Face flies are non-biting flies that feed on animal secretions, plant nectar and manure liquids. These flies may transmit pathogens responsible for infecting the eye and causing keratoconjunctivitis, or “pinkeye,” in cattle.

The life cycle of a face fly is approximately 21 days. Populations tend to peak in late summer.

Horn and face flies typically are not present at pasture turnout and do not reach economic thresholds for applying control until midsummer.

“The first step to determining when to apply control is to properly scout pastures and cattle to determine fly type and fly populations,” says Patrick Beauzay, a research specialist in NDSU’s Plant Pathology Department. “Horn flies typically rest on cattle throughout the day, whereas face flies land on the face of cattle for a meal and then retreat to nearby structures (forages, fences, etc.). Once threshold populations are achieved, control measures can be implemented.”

One control method is ear tags containing insecticides that are released slowly into an animal’s hair by movement. Ear tags should not be applied until fly populations are nearing the economic thresholds (typically from mid-June to July).

“Read insecticide container labels carefully because recommendations can vary in the number of tags to apply (one or two), age of cattle that can be tagged and chemical class of active ingredient (pyrethroid, organophosphate or a combination),” Beauzay says.

To help prevent resistance, he recommends rotating the class of insecticide each year and removing the tags when they no longer are providing effective fly control.

Stokka says that to achieve proper fly control, pour-on and sprays must be applied every two to three weeks throughout the fly season. Applying these products only before pasture turnout likely will not be an effective fly control method.

Back rubbers, dusters and other means of delivering insecticides, as well as non-chemical fly traps, also are available. Another option is natural fly defence mechanisms (dung beetle control of larvae). As with the other control methods, producers should watch for economic thresholds and determine what control measure will work best in their operation.

Monitoring populations to see if the product is achieving the desired level of control is important, the specialists say. If a product is not effective, the fly population may have developed a resistance to that type of insecticide, so producers should use another method and/or product.

“Pest control can be costly; however, producers can reduce costs by following principles of integrated pest management and applying the appropriate products at the appropriate time for optimum control of pest populations,” Meehan says.

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