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Controlling horn flies on cattle

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Column by Doug Shepherd, Hardin County Extension Service agent

By Doug Shepherd

Warmer weather brings more pest problems. Horn and face flies are key cattle pests in Kentucky. Both species breed in fresh pasture manure piles but present very different threats and management problems. Fortunately, there are a variety of options.

Horn flies are blood feeders. They remain on animals most of the time, taking 20 to 30 small meals per day. More than 100 flies along the sides and backs of each animal every day during fly season can mean 12- to 15-pounds lower weaning weights for spring calves and poor gains for older animals. The close association between the horn fly and the animal, however, makes many control methods quite effective.

On the other hand, face flies spend about 90 percent of their time resting off animals and visit them only to feed on liquids around the eyes and face. This makes some fly control methods more effective than others because face flies visit hard-to-treat areas for very short time periods.

One control option is insecticide-impregnated cattle ear tags which release small amounts of an insecticide distributed over the animal during grooming or rubbing. In general, ear tags provide excellent, long-term control of horn flies and some brands also reduce face fly numbers. Another advantage of ear tags is animals only have to be handled once. Read the label before you purchase and use insecticide ear tags. All tags are labeled for beef cattle while only those with certain active ingredients are approved for use on lactating dairy cattle. For fly control, it is best to tag animals after horn fly numbers reach 50 or more per side. This reduces the chances of developing resistance to the active ingredients. Normally, tags provide 12 to 15 weeks of fly control. Tagging too early in the season can mean the tags do not provide control in the fall that helps to control the overwintering population.

Another method of control is pour-on products. These are ready-to-use formulations applied to animals in measured doses based upon body weight. Horn flies are killed as they land on treated areas of the animal and pick up the insecticide through their bodies.

Typically, pour-ons provide about four weeks of fly reduction so they must be reapplied at intervals or used in combination with other methods. The length of control varies with weather and other factors, so re-treat when fly numbers build back up to about 100 per side but no sooner than label instructions allow.

Many cattle producers like to use self-application devices, such as dust bags, back rubbers or automatic sprayers for pasture fly control. They can be purchased ready-made or assembled from easily found materials. These devices can do a very effective job of horn fly control and may provide satisfactory to excellent face fly control. All require regular inspection and service to ensure they are working properly and may not be as mobile as other fly control systems. Location is important for these fly control methods. They must be put where animals can use them regularly. The number needed will vary with herd size, pasture area and other factors. The goal is for each animal to be treated regularly.

Horn flies and face flies breed in cattle droppings in pastures. Manure can be made toxic by having animals consume an insecticide that passes out in the manure. Mineral blocks or loose supplements which contain fly control products are available. This method is only a part of a total pasture fly control program because horn flies and face flies often move in from nearby herds. Supplemental control though the use of dust bags or back rubbers is needed to deal with these “fly-ins”.

Cost, effectiveness, past control history and herd management practices help narrow the list of options. For more information on fly control, contact the Hardin County Cooperative Extension Service, 201 Peterson Drive in Elizabethtown or call 765-4121.

CAIP GRANT APPLICATIONS AVAILABLE. County Agricultural Investment Program Grant applications are available at the Hardin County Extension Service at 201 Peterson Drive in Elizabethtown. The program is open to all Hardin County residents. Grant money is provided by the Kentucky Agricultural Development Fund and is allocated on a 50 percent cost-share reimbursement. Applications must be completed and returned to the Extension office by May 15. If approved, projects must be completed by Nov. 1. The Extension office is open 8 a.m. to 4:30 p.m. weekdays.

Doug Shepherd is a Hardin County Extension agent for agriculture and natural resources.