Different Flies Cause Varying Problems

REDFIELD, Iowa (DTN) -- Flies can be a problem in the spring and summer for cow herds. Using good control methods at the right time helps with the return on the investment.

North Dakota State University Extension veterinarian and livestock stewardship specialist Gerald Stokka said having a good pest management strategy can help provide effective control. This means the right kind of control at the right time for the right duration.

Having multiple ways to control flies can help prevent both health and economic losses.

"In beef cow-calf operations, applying pest control for lice and flies prior to pasture turnout will not be effective and will waste resources related to pest control," Stokka said. "Timing and the type of pest control depends on the species of flies."

TYPES OF FLIES CAUSE VARIOUS PROBLEMS

Horn and face flies are usually not seen until early summer and won't reach economic thresholds for applying control until midsummer. Horn flies are gray and look like small houseflies. If uncontrolled, they can attack cattle with as many as 120,000 bites per day. During peak times, as many as 4,000 horn flies can be on a cow's hide.

Elizabeth Belew, cattle nutritionist with Purina Animal Nutrition, said horn flies alone can account for up to an estimated $1 billion in losses annually for the U.S. cattle industry. "Early-season fly control for cattle goes a long way in keeping populations under control all season long," she said.

"The constant biting causes cattle pain and stress and can reduce the cattle's weight gains by as much as 20 pounds," Stokka added.

Face flies look like large, dark house flies. These are nonbiting flies that feed on animal secretions, plant nectar and manure liquids. These are the flies responsible for infecting the eye and causing pinkeye in cattle. These populations usually peak in late summer.

The stable fly is similar in size to house flies but have circular markings that distinguish them from horn flies. These flies feed on the blood, generally biting on the abdomen and legs. They are very difficult to control with pour-ons or injectable products.

DIFFERENT KINDS OF FLY CONTROL

There are several different kinds of fly control, and some may work better than others in certain environments. According to Belew, an effective and convenient way to deliver horn fly control throughout fly season is by feeding a mineral containing an insect growth regulator (IGR), which works for all classes of cattle.

"As cattle consumer mineral with IGR, it passes through the animal and into fresh manure, where female adult horn flies lay their eggs. The IGR prevents pupae from developing into biting adult flies," she explained. It is best to feed these 30 days before the last frost of spring through 30 days after the first frost of fall to ensure cattle are consuming the target level.

Colin Tobin, animal scientist at the NDSU Carrington Research Extension Center, said it's good to scout pastures to determine what kinds of flies are present and their populations. He said ear tags containing insecticides which are slowly released into the animal's hair by movement can be a good option, but shouldn't be applied until fly populations are higher in mid-June to July.

He suggested reading labels since different tags can be different in the number which should be used, the age of cattle that can be tagged, and the chemical class of active ingredients. Tags should be removed after they are no longer effective.

Pour-ons and on-animal sprays are another control option. These are typically applied directly on the animal's backline. The chemical is absorbed and circulates through the animal's system. These can control flies for up to 30 days before requiring another application.

"To achieve proper fly control, pour-on and sprays must be applied every two to three weeks throughout fly season," Tobin said.

The most effective fly control methods for forced-use situations are dust bags, backrubs and oilers. These should be placed where cattle enter frequently like a water or feeding site. Powder or liquid is used as an insecticide. Belew reminded that this takes frequent device checks to keep the insecticide stocked. Once cattle realize it helps them, they will use the devices more often, she said.

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

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