House fly and stable fly maggots develop in moist, spilled feed, and bedding or organic matter mixed with manure, in and around dairy barns. A successful control program is based on effective sanitation and manure management supplemented with timely applications of insecticides as needed. Fly control that relies mostly on chemicals is unlikely to be successful.
Following are tips to help with fly control in dairies:
- Sanitation and moisture management are the keys to any successful fly control program. Sanitation removes breeding sites. This should be done at about 10‐day intervals, or sooner, during the fly breeding season. Keeping accumulated manure, bedding and spilled feed as dry as possible until removed will make these sites less attractive for fly breeding.
- Screening and other mechanical control methods are invaluable in preventing flies from entering milk rooms and milking parlors. Air curtains are also of some use in keeping flies from entering these areas.
- Fly traps can capture large numbers of house flies, but generally do not reduce their numbers significantly. Ultraviolet light traps, bottle traps and fly sticky strips can be useful, particularly in the milk room where pesticide applications are limited and fly numbers are low. The solution to severe fly problems lies in finding and treating or eliminating breeding sites.
- Fly parasite release programs can be used to supplement fly control around concentrated livestock operations. These small wasp parasites, which are available from several commercial firms, lay their eggs in the larvae or pupae of house flies. The benefits of parasite release programs in livestock operations have not been proven to my knowledge. If you try them, including proper sanitation and chemical treatments will be essential.
- Insecticides can help control adult flies in milk rooms, but they must be used with extreme caution to avoid illegal residues in milk. Nonchemical means such as good sanitation; tight‐fitting, spring‐loaded screen doors and windows; sticky fly strips; and ultraviolet traps are preferred methods of control, supplemented by a comprehensive fly management program in the dairy barn. When pesticides are used, cover milk, milking utensils, bulk tanks and other containers before spraying. Follow label directions, and check with your local milk inspector before using any pesticide in the milk room area.
- Residual fly sprays applied to shaded or protected surfaces outside of milk rooms — for example, to walls, posts and ceilings in and around barns and loafing sheds — will kill flies that stay on the surfaces long enough to absorb a lethal dose. Residual sprays remain active for several days until they are broken down by sunlight or washed off by rain. Fly resting sites can be recognized by the accumulations of “fly specks” (feces deposited by flies). Remove animals from the barn before spraying, and allow at least four hours for spray to dry.
- Minimize house or stable fly control failures by rotating among groups of insecticides during the fly season. For example, with house flies, you can alternate between Group 1 and Group 3 for residual sprays, and use a bait from Group 4.
The entire publication can be accessed at http://pest.ca.uky.edu/EXT/Recs/ENT12-Dairy.pdf.