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Control fly populations, control herd health

Although fall is just around the corner, summertime flies remain a prevalent problem for cattle operations across the country where fly populations continue to grow, a Kansas State University (K-State) report suggests.

K-State medical and veterinary entomologist Ludek Zurek says the first step to controlling fly-related problems is to identify the species causing harm.

The following three fly species — horn flies, stable flies and house flies — are the most common. Zurek explains how to identify fly species and provides management tips for controlling each.

Horn flies

• Male and female horn flies bite and feed on the blood of animals. They are about half the size of house flies and usually gather on the shoulders, backs and sides of animals. On hot days, they move to the underside of the belly.

• Unlike other flies, they stay on the animal and leave only when disturbed or when females lay eggs in fresh animal feces.

• Control methods include ear tags, sprays, pour-ons, dust sprays and back rubbers. There are several brands for producers to choose from.

• One ear tag per animal is adequate. However, not every animal needs to be tagged for horn fly control. Tagging every third animal with one tag will provide good control since horn flies move between animals and eventually take blood from the tagged animal, which will kill the fly. Try rotating tags — two years on organophosphate tags, one year on pyrethroid tags, and so on.

Stable flies

• Male and female stable flies bite and feed on blood from animals and people. They leave black or dark red spots on surfaces where they rest.

• Bites on cattle most often occur on legs. Cattle react to stable flies by bunching up and standing in water, which helps protect from bites, but reduces feeding and decreases weight gain.

• Larvae develop in manure mixed with soil, straw or hay, as well as in decaying spilled grain and fermenting grass clippings. Development of the stable fly from egg to adult takes three to four weeks.

• Currently, there are no effective control methods for stable flies on pastured cattle. Minimizing hay waste or spreading wasted hay into thin layers may help stable fly problems, since research indicates that stable flies in pastures develop where round hay bales are fed to cattle during the winter.

House flies

• Despite their name, house flies can be found outdoors, as well as in. House flies do not bite, but can transmit food-borne and animal pathogens.

• House flies generate brown or yellow spots on walls and other surfaces where they rest. They are common from spring to late fall.

• House fly larvae can develop in any decaying organic substrate, including animal manure, compost and garbage. Under ideal conditions, house flies’ development from egg to adult takes only eight days.

• A good sanitation program that includes maintaining good drainage and cleaning around feed bunks, under fences and gates, and around water systems is key.

• Baits and residual sprays can also help control house flies. Baits are available in granular form or a form that can be dissolved in water for paint-on application. Sprays are applied where the flies rest.

Editor’s Note: This article was written by Crystal Rahe of K-State Research and Extension, which supplied this article.

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