How to Control Flies
on Your Horse, around the Stable and
Horse Barn – Part 2
I. TO PREVENT FLIES FROM BREEDING
Proper manure management and moisture control are the two biggest factors in preventing flies from breeding. Remove manure and wasted feed daily from stalls and pens and either spread it thinly to dry or compost it. Manure production on even the smallest horse farm requires constant attention. A thousand pound horse produces approximately fifty pounds of manure per day or about ten tons per year. Added to this is from six to ten gallons of urine which when soaked up by bedding can constitute another fifty pounds daily. In order to control odor, remove insect breeding areas, and kill parasite eggs and larvae, manure must be handled effectively.
There are basically three methods. All begin with daily collection. Once the manure is collected, it can be hauled away, spread immediately on a pasture or field, or stored for later distribution. Some refuse collection services are specially designed to handle manure or are willing to haul it away with other trash.
If manure is to be spread daily, it must be distributed thinly and harrowed to encourage rapid drying via the air and sun, thus eliminating favorable conditions for parasite eggs and fly larvae. It is best that such manure be spread on land outside of areas which will be frequented by horses during the current year.
The most common method of dealing with manure is daily collection and storage for later spreading. Composting reduces bulk, concentrates nutrients, and the fermentation process encourages the manure to release its nitrogen which diminishes odor and makes the manure more pleasant to handle. The end-product of composting is humus, a dark, uniform, finely-textured, odorless product that is valuable as a soil conditioner and additive.
Decomposition of manure begins with the formation of ammonia as urinary nitrogen decomposes. The level of fermentation depends on the degree of compaction and moisture content of the manure pile. A well-tamped but frequently turned pile makes the best environment for the aerobic bacteria necessary for fermentation. The pile should be uniformly moist. A dry pile simply dehydrates these desirable bacteria and a soggy heap smothers them.
While a manure pile is fermenting, certain portions of it could make inviting fly-breeding grounds. One way to discourage flies from congregating is to sprinkle the wettest portions of the pile with hydrated lime. The lime speeds up the bacterial action of fermentation and the “hotter” alkalizing action discourages flies from landing. The same lime is used to “sweeten” stall floors by lowering the acidity of the urine in the stall. It also causes the dirt particles to clump which allows air to more easily get at and penetrate the wet soil, thereby drying the floor.
The process of decomposition of a manure pile can take anywhere from two weeks to three months or more and the quality of the resulting product will vary. Managing a pile properly will kill the parasite eggs and larvae, prevent flies from breeding, and result in a good quality fertilizer. To this end, it is best to have three manure piles: one ready to spread, one in the process of decomposing, and one to which fresh manure is being added daily.
Before locating a pile, it is best to check local zoning ordinances. Be sure the pile is out of sight and smell of residences and down-wind from your stable and house. The pile must also have convenient access for daily dumping and periodic hauling. If possible, the piles should be located on a sloped concrete floor with four foot walls. Depending on the precipitation in your area and whether you are composting the manure to produce high quality fertilizer or just storing it to discard, the pile could be covered or open. In an arid climate, an open pile is subject to drying by the sun which decreases fertilizer value but also decreases flies. In a moist climate, an open pile is constantly saturated, so nutrients in the fertilizer are leached away and flies proliferate in the moist medium. Covering a pile with a roof, plastic sheeting, or earth may allow you to keep the moisture at an optimum level for decomposition and fly control. If an open pile must be used, it should be about six feet high and six feet wide and can be added to in length as needed until hauling is convenient.
Moisture should be controlled in all areas in and around the barn. Rake around feeders and waterers every day removing the moist feed that has been dropped. Pick up grass clippings, keep grass and weeds mowed, and pick up trash regularly. Be sure there is proper drainage in all stalls, pens, paddocks, and pastures. Repair leaking faucets, hydrants, hoses, and waterers. Eliminate wet spots in stalls and pens by clearing the bedding away, liming the stall floor, and letting the ground dry out. Barn designs that allow sunshine to dry the floors are best. Proper air circulation (via natural wind flow or fans) is essential. If possible have an extra stall or pen so you can rotate a horse out of his regular stalls for a day or two each month to let his stall dry.
II. TO PREVENT THE LARVAE FROM HATCHING
Feed-Through Oral Larvicide Feeding your horse an oral larvicide daily can prevent the development of flies in the manure. However, the chemical that kills the larvae also kills beneficial microorganisms such as the ones necessary for decomposing manure. Several brands of oral larvicide are available. The approximate 1 ounce daily dose costs from 4 to 30 cents per day, depending on brand and amount purchased.
FLY PREDATORS. Fly predators are tiny, nocturnal, stingless wasps that lay eggs in fly pupa. The wasp eggs utilize the contents of the pupa as food thereby killing the pupa before it can develop into a fly. The newly hatched wasps stay within two hundred feet of their emergence. Fly predators are naturally present wherever there are flies but not in large enough numbers to control an aggressive stable fly population. Commercially-raised predators are available for purchase. They are most effective if released early in the fly season and every 1-2 weeks thereafter. The success of the program depends on the severity of the fly problem, the number of predators released, and the management program. Methods of fly control involving insecticides must be carefully monitored or they will wipe out the predator population along with the flies. Fly predators are harmless to animals and people so they are a safe, non-toxic means of biological control.
Look for the final part of this fly control article in a future post.