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Controlling pest flies effectively with little or no pesticides on large livestock facilities is absolutely possible. However it helps enormously if you know what kinds of pest flies you have, where they are coming from, their life cycle and dependencies, to gain ongoing control with the least amount of work and expense. You don’t need to be a “fly geek” to have good results, but a little bit of knowledge goes a long way. So please take the time to read this information. Your animals (and spouse) will thank you for it.

It sounds simple but overall sanitation is the most important and effective way to control flies. The smart thing is to clean up the 10% of the farm that’s probably making 90% of your flies and let Fly Predators take care of the rest. You’ll spend less and get better results.

Identify the Fly:

The first step is to identify the insect(s) that are plaguing you and your animals. This is important as the variety of flies that bother your animals can come from dramatically different sources and knowing where to attack the problem is essential. For example, House Flies primarily reproduce in moist (not too wet and not too dry) manure, but Biting Stable Flies prefer rotting vegetation (spoiled feed and silage) over cow manure and Horn Flies and Face Flies reproduce only in pastured cattle manure that is undisturbed. Most of the common dairy pest flies are easy to identify by simply looking at your animals. If the flies are primarily on the legs or flanks, causing the cows to bunch and stomp, those are Stable Flies. If they are small and primarily on the back, those are Horn Flies. House Flies can be anywhere but they will be the large ones on the face around the eyes and muzzle.

Find the Maggots:

The second thing to do is look for larvae (maggots) as this will tell you where your fly breeding “Hot Spots” are. You’ll find larvae in moist manure areas or the wet edges of a silage pile or bunker, or the bottom of a round bale feeder, the spilled material outside a feed bunk or under a conveyer. Scratch below the surface to find them as they’ll never be on top. See a maggot or two, no big deal just make sure there are some Fly Predators near here. But if you see lots of maggots, this is a prime hot spot to clean up quick and put more Fly Predators near here. To control Horn Flies you will need to put Fly Predators in the pastures every 150ft.

Manage Your Manure:

For most commercial livestock operations manure management is THE most important variable in any House Fly control program simply because this is the largest single source of (from a fly’s perspective) “the good stuff”. There are two variables with manure that you can most easily change. The first is the quantity of manure, the second is the moisture content of that manure.

  • Move It:

    Hauling manure at least a 1/4 mile away in the summer no less often than every seven days is one option. This distance and time is important as flies generally travel no more than 1/4 mile (they can go farther) and they take at least 8 days to go from an egg to an adult fly at summertime temperatures (85°F). So rather than cleaning out the barn and piling it right next to it (which insures that ALL the flies coming off that manure will make it to your barn) stockpile it near where you will be spreading it far away.

  • Sink It:

    Fly larvae has to be in a medium that is between 40-60% moisture or it simply won’t complete its development. Increase the moisture of your manure by holding it in a liquid lagoon as a fly can’t reproduce underwater. But make sure that you do not let a solid crust form on that lagoon or you will have a huge fly factory there. The top of the cap will be too dry and the bottom next to the water will be too wet, but somewhere in the middle will be just the perfect moisture for optimum fly production. The cost of diesel or electricity to agitate it regularly, or adding bacteria to help keep it liquid, or installing a solids separator can be great investments in fly control.

  • Pile It and Compost It:

    In areas that receive regular summer rains collect the manure frequently and stockpile it in a pile. When you do this the manure that is deeper than six inches from the surface becomes too hot for a fly larvae to survive due to decomposition. So even if the pile is mountainous only the outer surface will reproduce flies. If you are not turning it, one big pile is better than a bunch of small piles as you are trying to minimize the surface area. A compost barn that is roto-tilled daily produces very few flies. Likewise composting in rows and turning frequently is very effective for creating great fertilizer and few to no flies.

  • Dry It:

    For areas that receive little moisture during the summer a good choice is to dry the manure. Best is daily collection and spreading manure thinly on crop areas or a concrete pad. Running a harrow or screen drag around your pens and pastures to break up the pats into smaller faster drying pieces can be very effective. Keep in mind that you are in a race with the flies as you want that manure to be less than 40% moisture by the 5th day from new. This is because at the optimum temperature of approximately 85°F it takes at least 5 days for a pest fly to pupate (form its cocoon) which is a really critical time for the moisture level. If it’s drier than 40%, the fly’s puparium (cocoon) doesn’t form properly and that particular fly is toast.

Clean It:

Do the best you can to clean stalls, corrals, paddocks, pens, drainage areas, loafing sheds, calf barns and hutches, feeding aprons, spilled feed and other decaying organic matter at no more than a seven day interval. If you remove the pupae before the flies have emerged, (8 days minimum) the difference can be enormous.

Don’t Overlook Spoiled Feed:

The Biting Stable Fly prefers rotting vegetation, not cow manure. So if you have these bad boys bothering your cows look for maggots in the wet spoilage at the outer base of a silage pile or on the front edge of the bunker, in a bedded pack barn by the fence, in calf hutches and pens bedded with straw, spoiled feed in front of or behind a feed bunk, the old feed at the bottom of round bale rings or the bottom of square bales. The best way to fix this is to spread out that spoiled feed and dry it. If you can, bed your calves.