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Fly season is just around the corner

Courtesy of Vernon County Extension Face flies congregate around the eyes, nose, and mouth and feed off of normal cattle secretions
TOO MUCH MILK: Face flies look more like the common house fly but are slightly larger and darker.
Beef Column: Get a head start on controlling the profit-sucking pests.

Warm weather with green grass, sunshine and all the insects that come with the heat will soon be here. For cattle, flies are some of the most troublesome external parasites.

There are numerous species of flies and all of them can have a negative impact on the productivity and profitability of your beef herd. Flies can reduce performance in cattle due to reduced grazing as they stop eating to swat at flies.

Some species of flies feed on blood from the cattle, others feed on normal secretions from cattle’s eyes and noses, and some lay eggs on cattle that develop into grubs under their skin. Several species spread disease from one animal to another. Other common species of flies that bother cattle include horn and face flies, deer and horse flies, stable flies, heel flies and house flies.

Top problematic flies

Horn and face flies are the two major species of flies that cause the most problems for Midwest cattle producers. Horn flies are considered the most economically damaging insect pest of pastured cattle. Horn flies are about one-half to one-third the size of the house fly and can be found more commonly on the backs, shoulders, sides, pool area, and the belly of cattle.

Adult female flies deposit eggs into fresh manure, and hatching occurs within one to two days. The total life cycle is 10 to 20 days, depending on temperature and time of year. They spend most of their life on cattle piercing the skin and sucking blood. This causes irritation and blood loss to cattle and, ultimately, decreases their weight gain. Horn flies can also transmit some blood-borne diseases.

Face flies look more like the common house fly but are slightly larger and darker. They do not bite, instead they congregate around the eyes, nose, and mouth and feed off of normal animal secretions. Females lay eggs in fresh manure and the total life cycle is about 21 days. Face flies are the main cause of pinkeye, so helping to control them can stop the spread of pinkeye. Pinkeye reduces average daily gains, due to pain and reduced eyesight, and often results in lower prices at the market due to visible eye problems.

With this understanding of the potential impacts, it is important to know control methods for horn and face flies. Horn fly control options include dust bags and strips, insecticide ear tags, pour-on products, oilers or sprays, and oral larvicides (insect growth regulators in minerals, for example).

Ear tags, pour-ons, and sprays can contain a variety of active ingredients, and some resistance has been documented for horn flies. To achieve full-season protection, use sprays or oilers early in the season and ear tags should be administered once fly numbers reach about 50 per side to reduce risk of resistance development. Make sure that dust bags or oilers are placed where cattle will frequent them.

Follow label directions

Always read and follow label directions. For face flies, effective control may require more than one method of treatment since the flies are not on the animal most of the time. Ear tags, dust bags or oilers, and sprays can be utilized. It is important to treat both the cows and calves to reduce face fly populations. Younger cattle require more attention than cows and bulls because fly prevention can have a direct economic effect on average daily gain and they are more susceptible to pinkeye.

Flies can have a negative impact on the productivity and profitability of your beef herd. Some of the above-mentioned methods for fly control can help reduce these negative impacts. Make sure to follow label directions and consult your veterinarian for additional guidance.

For more information about the beef industry, visit the Division of Extension Beef Resources website at livestock.extension.wisc.edu or contact your local Extension office.

Olson is the Vernon County Extension ag educator. This column is provided by the University of Wisconsin-Extension’s Wisconsin Beef Information Center

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