Several species of flies may be present around swine facilities. House flies are the most common, but the stable fly, little house fly and mosquito may also be present.
House flies are pests primarily because of their general annoyance to swine and other animals.
The stable fly, equipped with bayonet-like mouthparts for sucking blood, has an irritating bite, and several of these flies can severely hamper animal performance.
Mosquitoes, which breed in standing water around hog lots and in lagoons, can also cause great annoyance to animals by their biting activities.
Besides the importance of mosquitoes in disease transmission, house flies and stable flies have been implicated in the transmission of hog cholera and other human and animal diseases.
Sanitation: House flies, little house flies and stable flies develop in moist manure and wet, decaying organic matter of all kinds found around animal premises. No insecticide can be expected to control flies as long as breeding sites exist; therefore, a thorough sanitation program is a must to hold down fly populations in and around swine facilities. All manure, spilled feed, wet straw and decaying plant material should be removed twice a week to break the breeding cycle of house flies and stable flies (these flies can complete a generation from eggs to adults in as few as 10 days). This can be done by spreading manure and other waste material to dry or by placing it in pits or lagoons to become liquefied. If you use a liquid manure pit, do not allow accumulations of manure above the waterline, either floating or sticking to the sides, since this is ideal for fly production.
Insecticides: Residual premise sprays should give control for up to four weeks.
Knockdown sprays, with no residual action, should be applied when flies first appear in the spring.
Fly baits are most useful as a supplement to sprays. They alone cannot be expected to control fly populations.
Larvicides can be applied directly on manure and other fly breeding sources, but their use should be reserved for treatment of fly breeding spots not eliminated by normal sanitation practices.
For treating hogs and facilities with the listed insecticides, read and follow label directions for proper use of formulations and product chosen. A table in Purdue Extension E-9-W lists some insecticides recommended for fly control on swine and swine premises.
The publication is at https://extension.entm.purdue.edu/publications/E-9.pdf