Most cow/calf producers - about 81%, according to a 1997 report from the Animal and Plant Health Inspection Service (APHIS) - use some method of fly control. But only a small number have a well-managed program.

Cost, timing of control method and the inability to implement an adequate program due to lack of facilities or cattle spread out on range are the most common reasons cited for flies not being adequately controlled.

When setting up a fly control program for a customer, the first thing I show them is the fly number profile for the entire five to six months of the fly season. Although most producers realize that fly numbers peak in June, they don't realize there is also another peak in August, long after most control methods have been forgotten and the efficacy of the insecticide used has been drastically reduced.

In recommending programs, I try to coordinate the timing of the application of fly control to be as close as possible to June to give the best results. However, branding calves and sorting cows for the range may be done earlier, and producers do not like to handle cows and calves again just for fly control. Often, this timing is not possible because cattle are on range and away from adequate facilities.

Sanitation Is The Key Element In any fly control program, sanitation is the key element. Eliminating breeding places in manure, spoiled or rotten feed, and stagnant water is half the battle. Fewer adults means fewer eggs to turn into more adults. It takes stable fly larvae only 14 days to develop into adults. House fly larvae need only 10 days.

In proposing fly control programs, my first recommendation is to get an initial kill on the adult flies. If we don't knock down the adults, then the other methods will be overwhelmed and not give the desired results.

This is the major reason why most fly control methods fail. I recommend either spraying the cows or using pour-ons to achieve this initial kill. Buildings and corrals also may be sprayed to lower the adult population.

The next step is to determine another method of control. I always recommend at least two different methods. The use of a larvacide in a mineral is my method of choice for these fundamental reasons:

* Larvacides may be fed free-choice and may be used in most range conditions. Mineral feeders may not be allowed on some grazing permits, however.

* Larvacides fed in this manner do not require handling of the cattle.

* Larvacides act on a different stage of the fly life cycle (acting on the larva stage rather than the adult fly). No known resistance has been shown.

* I like to have some minerals available for both the cows and calves when the grass starts to mature later in the season and may be deficient in some vitamins and minerals.

Back Rubbers And Dust Bags Back rubbers and dust bags are also good methods of fly control that may be used around watering places and don't require much labor or expense. Mister-sprayers or foggers may be used around places where cows congregate to help reduce the adult flies. Fly tags may be used but need to be put on at the right time for best results. Be sure to use two tags instead of just one.

The 1997 APHIS study cited above found that of the 81% of cow-calf producers using some method of fly control, topical products (dust bags, dips, sprays, back rubs) were the most common form (61%) of fly control. Ear tags at 32% came next, then sprays/foggers (23%). Ranchers seldom used biological control, which reflects the transitory nature of the cow herd.

After initiating a fly control program, both the producer and I monitor fly numbers. Some producers think there should be no flies on the cows. Regardless of the methods used or the number of methods used, we will never be successful in eliminating all flies.

Our goal is to bring fly numbers below an economic threshold (generally fewer than 200 flies per animal). But we must take into consideration both the cost of control and the potential loss of production if no control is practiced.

One common misconception about fly control is that the insecticide itself may cause the flies to become resistant to insecticides. Mutant strains may develop but, as of now, are not commonplace.

Pesticide resistance may be better defined as the increasing ability of a pest population to survive exposures to the insecticide being used. This occurs when the more susceptible or weaker individuals in the population die, lea ving behind the stronger, more resistant individuals to produce eggs and further the more resistant flies. This is why producers should alternate insecticide types every year and use different types of insecticides within the fly control program.

Knocking down the adult fly population, practicing good sanitation, alternating fly tag and other insecticide types (pyrethoid or organophosphate), timing the control measures to coincide with both peaks of the fly population (June and August) and using multiple methods of fly control should be integral parts of setting up any fly control program.

Dave Wieland is a consulting nutritionist specializing in the cow/calf and feedlot segments. His client base is primarily located in the High Plains, Mountain States and Northwest. Based in Shepherd, MT, Wieland also publishes a subscription newsletter. For more information or answers to production questions, contact him at 406/373-5512 or e-mail at