Ag Notes: Controlling flies on cattle

Published 8:38 am Tuesday, May 15, 2018

Controlling flies on cattle

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

Horn flies are blood feeders. They remain on animals most of the time, taking 20 to 30 small blood meals per day. More than 100 flies along the sides and backs of each animal every day during the 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, does make many control methods quite effective.

On the other hand, face flies spend about 90 percent of their time resting off of 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 is that 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 that are being used. Normally, tags provide 12 to 15 weeks of fly control. Tagging too early in the season can mean the tags are not providing control in the fall that will help to control the overwintering population.

Another method of control is pour-on products. These are ready-to-use formulations that are 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 body.

Typically, the 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 will vary with weather and other factors so treat again when fly numbers build back up to about 100 per side but no sooner than the 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 be sure that they are working and dispensing 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 ultimate goal is to get each animal 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 are available which contain fly control products. This method is only a part of a total pasture fly control program because horn flies and face flies will move in from nearby herds. Supplemental control though the use of dust bags or backrubbers is needed to deal with these “fly-ins”.

Beef cattle producers have many alternatives for pasture fly control. Cost, effectiveness, past control history and herd management practices help to narrow this list. For more information on fly control, contact the Boyle County Cooperative ExtensionService.

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Jerry Little, County Extension Agent for Agriculture/Natural Resources