Fly Control

    The bite of a blood-sucking fly is painful and some horses have such a low fly tolerance that they can be driven into a snorting and striking frenzy or an injurious stampede.  Even fairly tough horses, subjected to a large number of aggressive stable flies, might spend the entire day stomping alternate legs which can cause damaging concussion to legs, joints, and hooves, and result in loose shoes, and loss of weight and condition.

    Stable flies breed in decaying organic matter.  Moist manure is a perfect medium.  The life cycle is 21 to 25 days from egg to adult.  A female often lays twenty batches of eggs during her thirty day life span.  Each batch contains between 40-80 eggs.  When the eggs hatch, the adult flies emerge ready to breed.  (The clouds of small flies on manure are often mistaken for immature stable flies but in fact are a different type of fly which may play an important part in the decomposition of the manure.)  The number of flies produced by one pair of adults and their offspring in thirty days is a staggering figure in the millions.  That's why fly prevention is the most important line of defense in your war against flies.

FIVE LINES OF DEFENSE IN YOUR WAR ON FLIES

    Your first line of defense is
TO PREVENT FLIES FROM BREEDING.

    For those flies that manage to breed, your second line of defense is
TO PREVENT THE LARVAE FROM HATCHING.

    If some of the larvae succeed in hatching, your third line of defense is
TO CAPTURE ADULTS FLIES IMMEDIATELY.

    To deal with flies that avoided the traps, your fourth line of defense is
TO KILL THE REMAINING FLIES.

    For flies that escape your previous four efforts, your fifth line of defense is
TO PROTECT YOUR HORSE.
 

 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.

III.  TO CAPTURE ADULT FLIES IMMEDIATELY AFTER HATCHING

    Fly Traps  Jar traps that utilize attractants can capture thousands of flies.  Some systems utilize muscalure, a sex attractant (pheromone) to draw the flies.  Others require the addition of fish or meat.  These traps, commonly used with a 1 or 2 1/2 gallon jar, can be smelly and must be emptied, then restocked.  Disposable traps are available for 1/5 the price of the jar traps.  They are designed to be used with the supplied sex attractant and water and claim to hold 10,000 flies.
Fly Papers  Fly paper is available in strips of several widths.  Some are designed to hang from the ceiling while others are to be tacked across doorways or aisles.  Some contain sex attractants, others are merely sticky.  A few brands contain insecticides, so it is important to read the label if you plan to use them around food or animals.  Fly paper is generally an inexpensive, disposable way of mechanically catching flies.

IV.  TO KILL THE REMAINING FLIES

       FLY ZAPPERS.  A mechanical way of killing flies is to use an electric fly zapper.  The flies are attracted to the light and are immediately killed upon contact.

        INSECTICIDES.  An insecticide is a chemical that kills flies quickly.  A repellent (covered later) is a substance that discourages flies from landing.  While insecticides are an important part of many fly control programs, much less has to be done with insecticides if manure and moisture are managed properly.  The indiscriminate use of any form of insecticide can result in the development of resistant strains of flies and can cause harm to horses, humans, and the environment.
        What type and brand of insecticide will work best for you will depend on your weather, fly problem, style of management, and each horse's sensitivity.  Finding the best insecticide involves a certain amount of testing for effectiveness and allergic reactions (both human and horse).
    Equine insecticides generally fall into one of four categories: pyrethrins ("natural" insecticides), permethrins (synthetic pyrethrins), carbamates, and organophosphates....listed in order from least toxic to most toxic and from least long-lasting to most long-lasting.  Insecticides are available in many forms for various applications.
    Topical sprays can be purchased in ready-to-apply forms or concentrates that are usually diluted in a 1:7 ratio of insecticide to water for house flies or a stronger mix for other flies.  Certain general livestock sprays are not safe for use on horses.
    Premises sprays are for use in and around buildings.  Some are not safe to use on livestock, manure, or bedding.  Long-term (up to six weeks) residual insecticides are designed to be applied on fly resting sites such as on rafters or in bushes.  Stable sprays are usually sold as concentrates which are diluted and applied with sprayers that range in cost from $20-100.
    Foggers are disposable cans of insecticide designed for the interior of buildings.  To use a fogger, close all doors, set the can to spray automatically until empty, keep the doors closed for 15 minutes, then ventilate the building.
Automatic misters are available in several types.  The disposable type uses an aerosol can set in a battery-operated automatic spray unit that delivers a spray every 15 minutes and lasts for about a month.  A unit is required for every 6000 square feet.  Electric fogger/misters are available for about five times the price.  Instead of using aerosol cans of insecticide, the electric misters have a reservoir that can be filled with a chosen solution.  Barn-wide automatic mister systems are incorporated in some large barns.  Since flies tend to congregate in certain places during certain times of the day, an effective use of misters is to aim them at the resting places and be sure they are functioning during fly siesta time.

    IMPREGNATED STRIPS.  Strips impregnated with insecticide are designed to keep approximately 1000 square feet free of flies for about 4 months so could be useful for enclosed areas such as tack rooms, feed rooms, and offices.  However, since there are a variety on the market, it is essential to read the package carefully as some are not safe to be used in enclosed areas where humans frequent or in areas where food is present.

    FLY BAIT (POISON)  The idea behind fly baits is to attract and entice flies to eat a specially prepared "food" that is laced with insecticides.  To that end, some baits contain sex attractants plus a sugar-based feeding enticer.  Fly bait can be used in hanging bait stations or as scatter bait on lawns and around buildings.  It is important to note the potential danger of other animals (birds, puppies, children) eating the bait.

V.  TO PROTECT YOUR HORSE
 
    REPELLENTS.  Repellents are available as spray, lotion, wipe-on, gel, dusting powder, ointment, roll-on, shampoos, and towelettes.  Repellents contain a substance irritating to flies, such as oil of citronella, and most contain some amount of insecticide (mostly pyrethrins and permethrins) as well.  Repellents can be water, oil, or alcohol based.  Oil-based repellents remain on the hair shaft longer but the oil attracts dirt.  Water-based repellents don't last as long but attract less dirt.  To increase the lasting effect, some water-based repellents are made with silicone which coats the hair shaft and holds the repellent in place longer.  Alcohol-based repellents dry quickly so are good for a fast touch-up but the alcohol can have a drying effect on the hair and skin.  Repellents can also contain sunscreen, coat conditioners (lanolin, aloe vera), and other products which increase lasting power.  Claims of duration of protection range from 1 to 14 days.  How long a repellent will last depends on the weather, the management, the exercise level of the horse (how much he sweats) and grooming (brushing, blanketing, and whether the horse rolls).

    FLY MASKS.  Fly masks are available in several styles.  Some protect the eyes while others protect the eyes, ears, and jowls.  Most are made of a mesh that allows the horse to see.
 
    FLY STRIPS AND TAGS.  Strips impregnated with repellent can be attached to halters.  Also available is a collar/brow band affair that has a breakaway feature.  These fly strips are particularly useful for controlling face flies and can last several months.  Face flies have sponging mouth parts and feed on mucus around the eyes and nostrils often causing inflammation and infection.  Some degree of relief can also be afforded a horse by using fly shakers (with or without repellent) attached to the crown piece of a halter or brow-band of a bridle.  These strips mechanically jiggle the flies off a horse's face when he shakes his head.
Fly Sheets  Cool, open-weave, mesh fly sheets keep flies from pestering the horse's body.  Consider using a repellent on the legs, belly and face in conjunction with a fly sheet.

    AN ASSISTANT.  In pre-chemical days, a human assistant was sometimes the fly-control method of choice.  While the farrier worked, his young assistant stood nearby with a fly chaser, a horse hair swish made from long tail hairs.  The assistant gently brushed away the flies that the horse couldn't reach with his "regular tail".