Getting Ahead-of-the- Summer Flies

  • Published: Friday, April 2, 2021

Getting Ahead of the Summer Flies

While it seems like summer is far away, now is the perfect time to plan the herd’s fly control program. Producers should be thinking about their fly control practices from last year and deciding if that approach worked to control flies or not. If not, a new plan should be considered.

Controlling fly populations is not only an animal welfare concern. Production losses due to high numbers of flies are seen through decreased grazing efficiency, decreased weight gain, and higher incidences of mastitis, pinkeye, and Infectious Bovine Rhinotracheitis (IBR) infections.

Horn flies – Horn flies are small flies found on the backs, sides, and polls of cattle. During the afternoons, these blood sucking flies can also be found on the bellies of cattle. Controlling horn flies can increase calf weaning weights by an average of 15lbs.

Face flies – Face flies are larger flies that feed on the secretions from livestock eyes, nose, and mouth. Very good at spreading pinkeye infections from animal to animal. While control is difficult, dust baths, oilers, sprays, or impregnated ear tags can be effective. Vaccinating for pinkeye is also important to avoiding pinkeye scarred eyes, especially in years like 2020, where face flies were particularly prevalent.

Stable flies – These flies bite the legs of cattle and can be major pests especially in feedlot cattle, dairy cattle, and horses. Stable flies are best controlled by weekly sprays and by cleaning up or dragging out moist feed or hay in winter feeding areas.

Fly Control Strategies

Fly larvae mature in moist areas 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 and reduce the flies produced. 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 a combination of fly tags later in the season with dust bathes or sprays earlier in the season can be very affective.

Dust bags, Oilers, 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% in comparison to forced use. When using oil, avoid using motor oil to avoid skin irritation. Quality mineral or fuel oils work better.

Pours-ons and Sprays - Pour-ons can provide a few weeks of protection from flies but cattle must be frequently worked to reapply the pour on throughout fly season. 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 (IGR’s) 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. It is suggested to start using 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 who lay their eggs in the fly pupa (cocoon) and feed on fly larvae. These wasps do not bother animals 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. Like the feed through products, neighboring flies can migrate to your farm so the use of fly predators are most effective in conjunction with another control method.

Regardless of what application of fly control is used, alternating class of insecticide used from year to year will reduce insecticide resistance in flies for better control. Further, using more than one fly control method with differing active ingredients can increase the control of fly numbers. Remember to follow label directions for safe application and follow any withdrawal times listed.

For more information, contact Elizabeth Picking, Livestock Specialist, at 417-256-2391 or at [email protected].



Writer: Elizabeth Picking

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Elizabeth Picking

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