University of Maryland Extension

Plan Now for Summer Fly Control

I don’t know about you, but I’m tired of winter! I enjoy a picturesque snowfall or two, but this year’s season has worn out its welcome. To get my mind off the cold weather, I’m thinking ahead to plans for the warmer days ahead.

Something that’s always a problem on the farm when hot weather rolls around is flies. They’re annoying to us, but they also spread disease and cause stress to livestock, which reduces their productivity. How are you going to control flies this summer?

The most effective control begins with preventing flies from breeding. Flies need three things to breed: material, moisture, and warmth. We can’t control the weather, so efforts should focus on eliminating breeding sites and managing against moist conditions. Be diligent to remove decaying organic materials like manure, soiled bedding, and spilled feed, which are favorite breeding sites.

Take efforts to maintain good drainage, too. Continually wet areas, like near  waterers become breeding sites as soon as organic matter (think manure!) is introduced. Heavy rain events are also common in summer, so strive to manage such that water quickly moves out and away from barns and animal areas. Weed control also affects fly control. Areas where weeds are allowed to grow thick and tall will stay wet longer and can hide manure.

The entire fly life cycle – from egg to adult – can occur in as little as 10 days, so it’s imperative to keep fly prevention on your weekly to-do list during the summer. Additional mitigation strategies will be of limited effectiveness if breeding sites are available.

Biological control via release of parasitic wasps is becoming more  popular. Female wasps lay their eggs in immature, developing flies; the wasp larvae feed on the developing flies, thus breaking the fly life cycle. Producers can now buy parasitic wasps commercially, but there isn’t much scientific data to support (or discredit) their effectiveness. Fly parasites won’t establish a population so they must be released several times during the season. Finally, they’re effective only against house flies and stable flies, so ensure these two pests are your major problem before going this route.

Feed through fly control is another option. Manure is an ideal breeding site for flies. Feed through products lead to manure containing chemicals that prevent eggs laid in manure from developing into adults. These products should be fed from just before the fly season – typically late March – through the first hard frost. They are effective in preventing fly development in manure but may not alleviate fly pressure if other breeding sites are available (such as manure from neighbors who do not use a feed through product).

A variety of insecticides are available in various forms: spray ons, dusts, ear tags, and more. With such a variety of insecticide products available, it can be daunting to choose which is best. It may be tempting to choose the least expensive option, but it’s true that you get what you pay for! In general, the higher the concentration of active ingredient, the more effective the product will be, the longer it will persist – and the higher the cost. If you do choose to use insecticides, use them with care, and always follow the directions on the label – it’s the law!

Maintaining good sanitation and drainage is key but likely won’t eliminate fly populations on the farm, making one of more of these additional practices necessary. Consider your costs, your management style, and your preferences to determine what will work best for you. Whatever you do, be sure to get a head start on flies this year by coming up with a plan now!


Maintained by the IET Department of the College of Agriculture and Natural Resources. © 2021. Web Accessibility

University programs, activities, and facilities are available to all without regard to race, color, sex, gender identity or expression, sexual orientation, marital status, age, national origin, political affiliation, physical or mental disability, religion, protected veteran status, genetic information, personal appearance, or any other legally protected class. If you need a reasonable accommodation to participate in any event or activity, please contact your local University of Maryland Extension Office.