ENTFACT-513: Insect Control for Horses, Horse Barns, and Stables  |  Download PDF

by Lee Townsend, Extension Entomologist 
University of Kentucky College of Agriculture 

This publication contains only a portion of the important information included on pesticide labels. Always read the product label carefully before buying and using any pesticide. Also, pesticide labels and registrations may change at any time. Any statements in this publication that disagree with the label must be disregarded. Many insecticides are sold under brand names that are not listed in this publication. No endorsement is intended for products mentioned, nor is criticism meant for products not listed. 

Several species of nuisance and blood-feeding flies, lice, and ticks attack horses from spring through fall. Key pests can vary regionally and are greatly affected by seasonal weather. In many cases, the breeding sites or sources cannot be managed so efforts must be directed at protecting the animals. A wide range of products are available but most contain only one or two common active ingredients. This publication provides representative types of products and points to consider in selecting control measures. 

While there seems to be a bewildering array of products, the list of active ingredients on each label will allow you to sort through them and look for similarities and differences. This information appears in a box below the brand name and includes the common name of the active ingredients (a.i.) and its % concentration. Each insecticide active ingredient has a common name (e.g. pyrethrins) that will let you recognize exactly what the product contains. Most have one or more of 3 main active ingredients. Often, additives are included to extend the length of protection or to provide some other feature to set the product apart from competitors. 

The most common active ingredients in products labeled for pest control on horses are pyrethrins and pyrethroids. Pyrethrins are chemicals with insecticidal properties that are extracted from the flowers of some species of Chrysanthemum. Pyrethrins provide very quick knockdown of insect pests and are safe for use on animals. Piperonyl butoxide is a synergist that is included in products to increase effectiveness; however, pyrethrins are broken down by sunlight so the residual protection lasts for only a few hours. The pyrethroids cypermethrin, permethrin, and resmethrin are synthetic forms based on natural pyrethrins. They are more stable than pyrethrins so protection from an application typically lasts for several days. Pyrethrins and pyrethroids work against a wide range of horse pests from flies and gnats to ticks and lice. They affect the nervous system of these arthropods, sometimes causing them to leave before they finish feeding. 

Representative products in this publication are grouped by application method and listed in increasing concentration of active ingredient. In general, the higher the concentration of active ingredients in a product, the longer the protection it affords. Products listed as concentrates must be diluted before use but may provide a more economical means of pest control in some situations. Check to be sure that the pests you want to control are listed on the label. 

Thoroughly brush horses before treatment to remove excess dirt and dust. Then, apply products over areas to be protected while brushing lightly against lay of the hair. Pay special attention to legs, belly, shoulders, neck, and face. Follow label instructions to protect yourself from exposure to the product when treating. Always apply to the face as a wipe and keep the insecticide away from eyes and mucous membranes. Check the label directions for re-treatment intervals. Also, look for age restrictions, some products should not be applied to foals under 3 months of age. Reapply each time the animal is washed or exposed to heavy rain. 

Sensitivity may occur after using any insecticide on animals. If signs of sensitivity occur, bathe your horse with a mild, non-insecticidal shampoo, and rinse with large amounts of water. Talk with your veterinarian immediately if signs continue. 

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Sprays and Wipes often come ready-to-use a in pump-spray bottle. The ingredients may be misted on or applied with a sponge, cloth, or glove wipe. 

Cypermethrin

• Bite Free Biting Fly Repellent (0.15%) + 0.20% pyrethrins
• Endure Sweat-Resistant Fly Spray for Horses (0.15%) + 0.20% pyrethrins
• Repel-X Lotion (0.15%) + 0.20% pyrethrins
• Tri-tec 14 Spray (0.15%) + 0.20% pyrethrins
• *Tri-Tec Concentrate Fly Spray for Horses (0.60%) + 0.8% pyrethrins 

Permethrin

• Bronco Equine Fly Spray (0.10%) + 0.05% pyrethrins
• Repel-35 RTU (0.50%)
• Flysect Water-Based Repellent Spray (0.15%) + 0.075% pyrethrins
• Flysect Super 7 (0.20%) + pyrethrins
• Bug Block (0.20%) + 0.10% pyrethrins
• DuraGuard (0.20%) + 0.10% pyrethrins
• Mosquito Halt Repellent Spray for Horses (0.20%) + 0.13% Prallethrin
• Manna Pro Equine Fly & Mosquito Spray (0.25%)
• UltraShield (0.40%) + 0.10% pyrethins
• Repel 35 Insect Spray Bio-Groom (0.50%)
• Zonk-It! 35 (0.5%)
• *Adams Concentrate (1%) + pyrethrins
• *Solitude Wipe-On Fly Repellent (1%)
• *Flysect Super–C Concentrate (1%) + 0.5% pyrethrins 

Pyrethrins + piperonyl butoxide

• Equisect Fly Repellent (0.10%)
• Fly Gone 7000 (0.10%)
• Flysect Citronella Spray (0.10%)
• Flys-X (0.10%)
• FlySpray 44 (0.10%) + citronella
• Pyranha Wipe n’Spray for Horses (0.10%)
• Wipe II Fly Spray with Citronella (0.10%)
• Flysect Repellent Spray (0.15%)
• Endure Sweat-Resistant Fly Spray for Horses (0.20%)
• Wipe Original Fly Protectant (0.20%)
• Super Shield Red Fly Repellent (0.25%)
• *Repel-Xp Concentrate (0.40%)
• *Horse & Stable Spray (0.5%) 

Resmethrin

• Absorbine Concentrated Fly Repellent (0.55%) 

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Roll-ons and Towels are ready-to-use products that can supplement fly control if protection is breaking down and flies are beginning to bite at specific sites on the horse. 

Cypermethrin

• Endure Roll-On for Horses (0.15%) + 0.20% pyrethrins 

Permethrin

• Bug Block Easy Wipe (0.20%) + 0.10% pyrethrins
• Ultra Shield Towelettes (0.40%) + 0.08% pyrethrins

Pyrethrins

• Flysect Roll-On (0.40%)
• Roll-On Fly Repellent (0.40%) 

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Spot-Ons are concentrated products that applied in small amounts to specific sites on the horse. The active ingredient becomes distributed over the animal and protection may last longer that sprays or wipes. Reactions in horses may include skin sensitivity, increased itchiness, redness, rash, and hair discoloration or hair loss at the application site. 

Spot-Ons (permethrin)

• Brute Pour-on Insecticide (10%)
• Celebration Spot-on for Horses (45%)
• Durvet Fly Rid Plus (45%)
• Equi-Spot Spot-on Fly Control (45%)
• Freedom 45 Spot-on (45%)
• UltraSpot (45%) 

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Dusts are fine particles of talc or clay that carry the insecticide. They may be useful in specific instances, such as louse control. Coumaphos is an organophosphate insecticide. 

Coumaphos

• Co-Ral Zipcide Equine & Livestock Dust (1%) 

Cypermthrin

• Python Dust (0.075%) 

Permethrin

• Horse Lice Duster III (0.25%)
• Prozap Insectrin Dust for Livestock & Poultry 0.25% permethrin 

Horse bots are bumble-bee like flies that glue their eggs (nits) primarily to hairs on the forelegs or under the jaw. The flies are active from mid-June until frost. They do not bite but can frighten horses and cause them to run. The eggs hatch in response to moisture and friction as horses lick or nibble at areas where the eggs are attached. The larvae (maggots) attach in the stomach or intestine and remain there as parasites until the following summer. Several hundred larvae can be present and cause enough irritation to interfere with digestion. Mature larvae will pass out in the feces. They will dig into the soil, pupate, and emerge as adults. There is one generation each year. Adult bot flies die following a killing frost. 

Physical control options during the summer include trimming or removing hairs with nits using clippers or a bot egg knife. This must be repeated as eggs are noticed again on the animals. 

Several formulations of ivermectin, a dewormer and bot control product, are available for use after fly activity ends for the season. Examples include Agri-Mectin, DuraMectin Paste, Equimectrin, Ivermectin Paste, IverCare, and Iverease. Quest Equine Gel (moxidectin) also is registered for control of bots and other internal parasites. 

FLY CONTROL AROUND HORSE BARNS AND STABLES

House flies and stable flies are common pests around horse barns and corrals. The persistence of house flies makes them very annoying; as potential carriers of human and animal pathogens, they also are a health threat. Stable flies give painful bites to animals and humans, making activities unpleasant and potentially making horses nervous and difficult to manage. 

House flies visit most any moist material from manure and decaying organic matter to garbage to blot up a liquid meal with their sponging mouthparts. They can carry a range of pathogens (causing intestinal disorders, eye infections, etc.) on their seemingly restless journey. Females may deposit batches of eggs as they feed on a variety of moist, fermenting organic matter, manure, rotting hay, feed silage, or garbage. The cycle from egg to adult takes from 7 to 14 days, depending on environmental conditions. Mature larvae will crawl to drier sites to pupate and emerge as adults. 

The stable fly resembles a house fly but has a distinct piercing mouthpart that projects from the front of its head. Males and females are blood feeders, usually attacking the flanks or below the knee causing horses to stamp or kick themselves. The fly is on the animal for only a few minutes; after feeding it moves to walls, fences, or other surfaces to digest its meal. Stable fly maggots develop in decaying organic matter. A fermenting mixture of straw, spilled feed, or hay, and urine or water is ideal. Horse manure is usually too dry but becomes suitable if moistened. Females lay several batches of 40 to 80 eggs. Development from egg to adult takes 21 to 25 days during the summer. 

Elimination of breeding site is the key to a successful fly control program. Barns and corrals should be cleaned once a week to break fly life cycles. Removed manure and other fly breeding materials should be spread thinly over appropriate area or composted, as practical. Maintain good drainage to eliminate wet manure, spilled feed, and hay or straw. Check for and correct wet areas around animal waterers. Dry manure and accumulated organic matter are not good breeding sites. 

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House flies and stable flies need: breeding material, optimum moisture, and adequate warmth to develop. A successful fly control program must rely on timely elimination of breeding sites and moisture control. Insecticides can help to provide some temporary reduction of house fly and stable fly populations but cannot be the basis of fly management. 

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Mechanical Control and Biological Control

• Screening is an excellent way to keep flies out of feed and tack rooms and box stalls.
• Fans that direct a downward and outward air flow will keep flies from entering barns.
• Fly traps and sticky paper will capture flies. They may be most useful as a means of documenting fly numbers over time. A significant increase in catch from one week to the next can be a warning to check on sanitation and to increase fly control measures.
• Several commercial firms offer a fly parasite (predator) release program that can be used to supplement fly control. Aspects of using biological control are covered in Entfact 502, Biological Control of Flies. 

Insecticides as Supplements to Fly Control

Insecticides generally are used to kill adult flies after a problem has developed. While they can help to reduce fly numbers, they do not address their source – moist breeding materials. There are many alternatives for fly control but they should be viewed as a temporary solution until the root cause of the problem can be corrected. Large numbers of flies mean lots of breeding sites and a situation that cannot be corrected by insecticides alone. 

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Residual insecticidesare applied to walls, ceilings, and rafters of barns and sheds where flies rest. General observations and accumulations of fly specks (waste drops) will help to identify these spots. Be sure to protect water and feed when making applications. In order to minimize control failures due to insecticide resistance, do not apply the same insecticide or insecticide within he same chemical class repeatedly throughout an entire season.

Space sprays, fogs, and mists can provide a quick knockdown of flies, especially in enclosed areas. Systems vary from foggers to timed release aerosols. Usually, these are pyrethrins with very short residues so treatments have to be repeated. 

Pyrethrins – many ready-to-use and concentrate formulations 

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Fly baits can be placed in bait stations. They are most effective when there are few competing food sources in an area. Baits attract and kill house flies but are not effective against blood-feeding stable flies. Animals must not have access to these materials.

• Imidacloprid
• QuickBayt
• Methomyl
• Apache, Blue Streak Fly Bait, Fatal Attraction, Golden Malrin, Tailspin
• Trichlorfon
• Dipterex 

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Larvicides are insecticides that can be applied to breeding sites where large numbers of maggots are present and the area cannot be cleaned in a timely manner. Rabon (tetrachlorvinophos) is labeled as a manure spray to kill maggots. 

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Feed through insecticides are administered specific levels in animal feed and pass out in the feces making the manure toxic to developing maggots. Each animal must get the correct amount every day. while they can reduce fly production from manure, they do not address problems with wet spilled feed and straw.

Issued: 5/07 
Revised: 12/12 

CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication. 

Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE! 

Images: University of Kentucky Entomology