Fly control strategies

Fly larvae mature in moist places like manure piles and winter-feeding areas. Dragging pastures and feeding areas to break up manure piles and wet feed or hay will dry out those fly larvae habitats. This practice can be used in conjunction with many different types of insecticide control such as:

• Fly tags. Fly tags can be effective on cows and weaned calves. If using fly tags, buy high-quality tags, put them in when fly numbers are relatively high, and remove them in the fall to reduce potential horn- and face-fly resistance. Using fly tags later in the season with dust baths or sprays earlier in the season can be very effective.
• Dust bags, oilers and back rubbers. Dust bags, oilers and back rubbers are most effective when cattle are forced to use them to get to mineral feeders or water sources. Free-choice use of dust bags reduces the efficacy by 25%-50% compared to forced use. When using oil, don’t use motor oil, which can cause skin irritation. Quality mineral oil works better.
• Pour-ons and sprays. Pour-ons can provide a few weeks of protection from flies. If using sprays, complete coverage of the animal provides more control. Both pour-ons and sprays need to be reapplied frequently throughout the fly season.
• Feed-through products. Feed-through fly-control products like oral larvicides and insect growth regulators prevent fly larvae from maturing in manure piles. Feed-through products need to be fed continuously, beginning before flies become a problem. Waiting until flies are heavy to begin a feed-through product is not ideal because the active ingredients take time to end up in the cow’s manure. Consider a fly-control mineral 30 days before the last frost in spring and ending after the first frost in the fall. The downside to using a fly-control mineral is that fly populations may migrate from neighboring farms.
• Fly predators. Fly predators are small, non-stinging wasps that lay their eggs in the fly pupa (cocoon) and feed on fly larvae. These wasps do not bother livestock or people. To see a long-term reduction in flies, new predators need to be added to manure piles every month from April through September. As with the feed-through products, neighboring flies can migrate to your farm, so fly predators are most effective in conjunction with another control method.

Regardless of what application of fly control is used, alternating classes of insecticides from year to year will reduce insecticide resistance in flies for better control, says Picking.

“Using more than one fly-control method with differing active ingredients can increase the control of fly numbers,” she says. “Remember to follow label directions for safe application, and follow any withdrawal times listed.”

Vaccination

While there are vaccines to protect against pinkeye, the success rate varies.

There is a way to pinpoint vaccines to a particular herd, Picking adds. “Several veterinarians in my area have started swabbing local herds to create their own autogenous vaccine for the area. I know quite a few producers [who] have gone to using the autogenous vaccines, as well.”

The ideal time to vaccinate is before the detection of any clinical signs of pinkeye, according to Evans.

“Although most vaccines currently available ‘require’ a single injection, a report from Dr. John Angelos with the School of Veterinary Medicine at the University of California–Davis suggests that a booster three to four weeks after the first injection might help decrease the number of animals affected and, especially, would help lessen the severity of the clinical signs observed,” Evans says.

Treatment with patches on affected eyes can decrease healing times. Antibiotics can also be helpful in some circumstances; they should only be used after consulting with your veterinarian, Evans advises.

Editor’s note: This article was provided courtesy of University of Missouri Extension. Julie Harker is a College of Agriculture, Food and Natural Resources Extension news strategist.

Angus Beef Bulletin EXTRA, Vol. 16, No. 8-A