With summer upon us, so are the problems associated with fly infestations of cattle. Economic losses occur because flies torment cattle, sucking blood from the animals and spreading diseases such as pinkeye.
However, effective control measures can keep fly populations down, which, in turn, will boost profitability in cattle operations.
The first major fly that affects many cattle is the horn fly.
It is so named because it often rests on the horns of cattle, but with modern polled cattle the flies tend to rest on the withers, backs and sides. Additionally, they spend time on the undersides of cattle, where most of the biting occurs.
Losses associated with horn fly infestations have been studied extensively. The crucial level of flies for economic losses is 200 to 250 per animal. If either young animals or cows have 200 or more flies, then treatment will result in increased weight gains.
Studies performed at Texas A&M University have documented average increases in weaned calf weights of 20 to 27 lb. when horn flies are effectively controlled.
The second major fly affecting cattle is the face fly.
This fly is larger and more robust than the horn fly and spends only periodic feeding times on cattle during the day. As the name implies, these flies prefer to be on the face, where they consume secretions from the eyes and nostrils.
Face flies are particularly important because they transmit the pinkeye organism from one animal to another. Their feeding can damage the cornea of the eye, allowing a port of entry for the pinkeye-causing organism.
A number of methods and products are available for the control of cattle flies. Topical products that are currently approved fit into three major categories: organophosphates, pyrethroids and avermectins (abamectin).
Pyrethroids have, to date, given the best face fly control because of their repellency.
Among the other effective products approved for fly control are feed-throughs. Since both horn and face flies lay their eggs in manure and develop there, these products prevent fly development in manure pats.
An important consideration in the use of feed-through products is the presence of other untreated cattle in the area.
If there are producers within one to five miles who do not use these control products, you may not see the full benefit of your treatment plan. Because of that, work with your neighbors if possible.
It is also important to understand that full-season control from ear tags is generally not possible. That’s why an integrated fly control program is recommended.
Dust bags, backrubbers, oilers, face mops and other “self medicators” can be effective because they help to provide long-term control. But carefully choose locations for these treatments so that your cattle have frequent contact with them.