Controlling Fly Populations Around Cattle

By Hubert J. Karreman, V.M.D.

For external parasites like flies, we again need to consider areas where moisture builds up, especially areas with big accumulations of moisture-laden manure. Fly populations explode with humid air, heat, thundershower activity, moisture/sweat, and manure on the animals to attract them. Of course we cannot control the weather, but we can determine what kind of environment our animals live in. Do they slop around in “soup” near their feeding area (including round bale feed area


Do they lie in areas that are moist and damp? Do they lie under the only tree in the pasture, making a mud hole? Is there such a buildup of bedding in their outdoor superhutch that a slow, steady trickle of fluid is draining away from it? Are the animals forced to plunge their faces down through tall, rank pasture growth to get at the more lush vegetation nearer to the ground, leading the cows to prick their eyes on the taller, less-appetizing plants and causing tearing (moisture)? Tears running from the animals’ eyes makes for pinkeye in short order. All these conditions attract flies, in addition to stacked manure that is aging (stacked either on purpose or due to “natural” buildup from not being mucked out regularly).

Keeping areas “clean and dry” are key to reducing fly populations.

“Clean and dry” are cardinal terms for the keeping of livestock. While the best efforts to keep animals clean and dry can still be op­posed by weather conditions that encourage flies, it is the foundation for pest prevention, to be put in place before trying “Band-Aids” to help during problem times.

Methods of reducing the effects of flies include sticky tape, phero­mones to attract flies into traps, tunnel ventilation (moves air so flies cannot land and keeps the animals drier), tails on cows to swat flies away, pouring liberal amounts of field lime on the animals to keep the moisture/sweat away, and proper nutrition (as flies seem to be attract­ed to animals that are sick, have liver problems, etc.). Then, after all these are incorporated, a fly-spray like Ecto-Phyte (Agri-Dynamics) will help quite a bit. But do not simply rely on a natural fly spray in­stead of an organophosphate fly spray. The difference between simple-minded input substitution and a wise, holistic, multipronged approach will become readily apparent.

FOR EXTERNAL PARASITES, like flies, we again need to consider areas where moisture builds up, especially areas with big accumulations of moisture-laden manure.

Four-Seasons Organic Cow Care

Types of Flies

Horn flies are smaller than other kinds of flies and are usually found on the bellies and backs of cows. Horn flies deposit eggs in fresh manure, and they take nine to twelve days to develop into adults. They take ten to twelve blood meals per day and can transmit Staphylococcus aureus between animals. Face flies also lay eggs in fresh manure and become adults in fourteen days. Face flies have been found to carry more than thirty bacterial diseases and are the main carriers of the pinkeye bug. Stable flies are found on the lower body and legs of cattle and take about two to three blood meals a day. They prefer aging manure and bedding or round bale feeder areas to deposit their eggs. Cattle bunch up trying to avoid their painful bites. House flies will use a variety of organic materials to lay their eggs, and it takes about seven days for them to become adults.*

Source: Four-Seasons Cattle Care; Wes Watson and Steve Demming, “Managing Parasite Flies in Pasture-based Dairy Systems,” presented at the Mid-Atlantic Grazing Conference, July 2012.