Livestock and Livestock Building Pest Management

Bulletin 473

Control of Flies in Milkrooms

Extremely small amounts of pesticides can be detected in milk, and their presence is often illegal. Check with sanitary codes (federal and state) regarding legality of a pesticide in the milkroom. It is illegal to use baits, residual surface sprays or space sprays other than those containing pyrethrins plus synergist or permethrin. For best fly control and to avoid illegal residues, use the following steps:

1. Reduce the number of flies entering the milkroom by practicing strict sanitation and use recommended insecticides in dairy barns and premises.

2. Make sure good, tight-fitting screens are on the milkroom doors and windows. Use screens, 14 to 16 meshes to the inch, made of copper, aluminum, bronze, plastic or rust-resisting materials. Keep spring-loaded doors shut at all times. Electric-powered "air-curtain" fans will discourage flies from entering doorways.

3. GardStar 40 percent EC Livestock and Premise Insecticide can be used as a 0.469 percent permethrin, water based, space spray when used as a fog or fine mist using 2.0 fluid ounces per 1,000 cubic feet. Use a mist or aerosol space spray of 0.06 to 0.1 percent pyrethrins plus piperonyl butoxide oil-based fly sprays when other methods fail to give adequate control. To prevent milk contamination, cover milk, milking utensils, cans, bulk tanks and containers before spraying. (Follow label directions and safety precautions.)

4. Use sticky fly strips where appropriate, such as Lure Fly ribbons, Fly Stik with Muscalure or aluminum foil sticky fly trap paper (fly illustrations on paper to attract other flies).