Fly Control for Cattle





Flies rob millions of dollars from cattle producers each summer. Losses are due to reduction in gain on yearling cattle, loss of body condition in cows and bulls and lowered weaning weights in calves. These losses are all due to stress. We have all seen cattle that are bothered by flies. They spend a tremendous amount of energy trying to get relief from the flies. They go to shade in brush or tress, stand in ponds or creeks, swish their tail constantly and flick their ears all in an effort to get rid of the flies. All this effort and time takes cattle away from grazing, ruminating and doing what cattle do to make you money.

Flies spread diseases; the most common in summer is pinkeye. They also feed on blood, which reduces performance. One study determined that yearling cattle with a high infestation of flies had a 12 to 15 percent reduction in gain, which equaled about 30 pounds.

There are two main flies that cause the most problems for area cattle producers. Those two flies are the horn fly and the face fly. Let’s talk about both species.

Face flies are those pesky critters that you see, like their name implies, on the faces of cattle. The flies you see on the cattle are the female face flies. They are the only ones that feed on the secretions around the eyes, nose and mouth of cattle. They are non-biting flies but they suck up the secretions to get the protein contained in the secretions. The male face flies spend their time resting on brush, trees and other vegetation waiting on mates. The males feed on plant nectar and manure.

The female face fly lays her eggs in fresh cow manure. They do not lay eggs in manure piles around barns or in feedlots. When the face fly eggs hatch, the maggots feed on the manure and then move to the soil to pupate. The flies then emerge about a week later. The time it takes to get from the egg to an adult is two to three weeks. Face flies are most active during the summer and early fall. When the weather starts to change in the fall, the flies look for shelter in some building to hibernate.

It has been proven that a population of over 12 flies per animal will decrease grazing by about an hour per day. This of course will result in a loss of productivity. When populations are over 20 flies per animal, it is considered a heavy population. Heavy face fly populations will cause cattle to seek relief and reduce grazing time and performance substantially. It is recommended that face flies should be controlled when there are five to ten flies per animal.

If you had to pick a bad guy of the fly family, it would be the Horn Fly. Horn flies are those flies that you see in clusters on the backs of cattle, usually around the top of the shoulders. These flies may move to the sides or underneath the belly of the cattle if disturbed or when the weather gets really hot.



Horn flies have a piercing mouthpart and feed on the blood of cattle. They eat about 20 to 40 meals per day. Just think about how much these flies are bothering your cattle. I can’t stand to get even one mosquito bite. Think about having 100 of these horns flies, biting you 40 times each day to feed on your blood. Believe me you wouldn’t be interested in eating; you would be trying to find a way to get them off of you. That is exactly what the cattle do. High infestations of these flies can really rob you of gain and performance because the cattle spend their entire day trying to get relief from the constant biting.

Horn flies spend their life on cattle. The females leave only to lay their eggs in fresh manure that is less than two minutes old. They can lay up to 500 eggs on the grass underneath the manure. In a few hours the eggs hatch and the maggots feed for a couple of weeks before pupating. The life cycle from egg to adult is about three weeks. When the adults hatch, they immediately try to find cattle and the biting and feeding begins.

Horn flies die off with the first frost. They over-winter in the pupal stage and hatch again in the late spring when the weather warms up.

In order to determine if you have a high enough population to justify a treatment program, count the number of horn flies on the heads, backs and shoulders of 15 head of cattle. Take the average number and if you have 100 flies per animal you have reached a treatment threshold.

The economic threshold, where the flies are causing you economic losses, is 200 flies per animal. As mentioned earlier in this newsletter, high populations of especially horn flies can really reduce cattle gain, performance, milk production and weaning weights.

Cattle producers have a number of treatment options that they can choose from to control face and horn flies. To control horn flies the options include:

1. Back rubbers that have an insecticide diluted with some type of oil.

2. Dust bags—are good as long as the cattle will use them. It may have to be placed next to a water source or mineral feeder to force the cattle to walk under/through it.

3. Feed additives in mineral mixes. These pass through in the manure and disrupt the normal pupation process thereby controlling the flies. Each animal needs to consume the recommended dosage for effective control.

4. Insecticide ear tags – most effective if applied when the flies start to become a problem. If applied too early in the season the tag may have already lost some of its effectiveness when the fly season hits.

5. Pour-ons and insecticide boluses are also a choice.

6. Walk through fly traps placed in gates where cattle must walk through them regularly, are a control measure that works without the use of insecticides.

7. High-pressure insecticide sprays that are applied to treat the entire herd while held in a corral are another choice that is highly effective.

Face flies are a little harder to control than horn flies because they don’t spend all of their time on the cattle. Control options include: Insecticide ear tags. Dust bags. Walk through fly traps.

It has been proven that Horn and Face flies can cause economic losses if populations exceed threshold levels. With a 15 percent reduction in gain and performance on cattle when fly numbers are high, it makes sense to address the problem.

(by By Dona Geode, University of Missouri Extension Livestock Specialist)