This article was originally published in Wisconsin Agriculturist Magazine

Summer is here with the green grass, sunshine and all the insects that come with the heat. 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 swat at flies and not eat grass. Some species of flies feed on blood from the cattle, others feed on normal secretions from cattle eyes and nose, and some lay eggs on cattle that develop into grubs under their skin. Several species   spread disease from one animal to another. Some common species of flies that bother cattle include horn and face flies, deer and horse flies, stable flies, heel flies, and house flies.

Horn and face flies are the two major species of flies that cause the most problems for Wisconsin cattle producers. Horn flies are considered to be the most economically damaging insect pest of pastured cattle. Horn flies are about 1/2 to 1/3 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 females deposit eggs into fresh manure and hatching occurs within 1-2 days. The total life cycle is between 10-20 days depending on temperature and time of year. They spend most of their life on cattle piercing the skin 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 eye sight, 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 of 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 (IGR) 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/oilers are located where cattle will frequent them. 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/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.

References:

Halfman, William. Fly Control on Cattle is Critical. UW Division of Extension article 06-06-2011.

Harty, Adele. Fly Control Considerations for Cattle on Pasture. SDSU Extension article 6-10-2020.

Boxler, DJ. Nebraska Management Guide for Insect Pests of Livestock and Horses.  University of Nebraska-Lincoln Extension Publication EC-1550.

Townsend, Lee. Insecticide-Impregnated Cattle Ear Tags. University of Kentucky Department of Entomology Extension Fact Sheet,  ENTFACT-505