Managing Insect Pests of Horses

A l a b ama A & M a n d A u b u r n U n i v e r s i t i e s Managing Insect

ANR-464 Pests of Horses sound internal and Aexternal parasite control program is very valuable to horse owners. Parasite control is an important part of a complete horse health program, which should also include good feed, shelter, regular exercise, foot care, vaccinations, and protection from accidents and contagious diseases. Such a health program requires an investment of time, money, and manage- ment skills, but it can result in strong, bright-eyed, glossy- coated, and economically desirable horses. This publication discusses and illustrates common insect pests of horses. Parasites cause direct and indirect damage to horses. They can spread diseases and cause digestive upsets, Photo of Scotch Bar Time courtesy of Stauffer Farms, Bearneveld, Wisconsin. poor condition, retarded ARCHIVEOrganizations that sponsor horse horses requires a good understand- growth, and death. Fright shows, fairs, sales, or breeding ing of the life cycles and biology of and irritation caused by sheds should encourage and use insect pests. egg-laying adult bot flies strong parasite control programs. Horse owners often depend on Flies may cause animals to inflict veterinarians for the latest technical damage to themselves or to information and the most efficient There are several species of flies that are pests of horses. Flies typi- anyone handling them. means of managing internal parasites. Managing external parasites on cally have only one pair of wings and have a complete metamorphosis www.aces.edu (life cycle) characterized by four life on blood. Horse flies and deer flies stages—egg, larva, pupa, and adult have cutting and slicing mouthparts (Figure 1). that they use to cut through the skin Flies may have one of three and tissue to the blood. After intro- basic types of mouthparts (Figure ducing an anticoagulant, these pests 2). Sponging mouthparts, found on suck the blood as it oozes from the house flies and face flies, are used wound. However, some flies, such to sponge or sop liquid foods. Stable as bots and cattle grubs, have no flies, horn flies, and mosquitoes mouthparts as adults. use their mouthparts to pierce the Flies breed in a wide variety of animal’s skin so the flies can feed habitats, ranging from manure and garbage to the living tissue of animals.

Adult Horse Bots a b c Bots are the larvae of bot flies (gad flies) and are the most damaging stage in the life cycle. The Figure 4. Eggs of horse bots: (a) the nose bot fly, G. hemorrhoidalis; (b) the common adult flies are only superficially ir- bot fly, G. intestinalis; (c) the throat bot fly, ritating while laying eggs. Contrary G. nasalis to popular belief, adult flies have under-developed mouthparts and cannot feed or bite. They are about the same size as honeybees (1⁄2 to 3⁄4 inch long) but are covered with either black and yellow or all black Eggs hairs (Figure 3). Adults are active in Alabama from June until frost in October or Pupa November. Females lay 150 to 500 eggs in a life span of 7 to 10 days. The location on the horse where the eggs are glued indicates which type they are of three species that are found on horses. The eggs can be readily seen on individual hairs (Figure 4).

Larva

Figure 1. Typical fly life cycle

Figure 5. Larva of the horse bot fly Sponging ARCHIVEPiercing Mouthparts Mouthparts (side view) (side view)

Figure 3. The horse bot fly

Cutting Mouthparts (front view)

Figure 2. Three basic types of fly mouthparts

Alabama Cooperative Extension System BOTS (Larvae) inside horse 8 to 10 months, from first frost to late spring

Figure 6. Stomach and duodenum of horse with clusters of larvae of G. intestinalis and FLY EGGS G. nasalis, respectively on hairs 7 to 14 days

PUPAL STAGE on pasture 4 to 8 ADULT FLY weeks lives 7 to 10 days and in early lays up to 500 eggs ADULT FLY summer emerges from middle to late summer

Figure 8. Life cycle of the common horse bot fly, Gasterophilus intestinalis

and duodenum. Large numbers of wall and eventually death. larvae in the gums may cause pus When the bot larvae are mature, pockets and mouth irritation. they detach themselves, change into The female nose bot fly, G. hemor- the non-feeding prepupal stage as Figure 7. Bot fly eggs on leg of horse rhoidalis, deposits black eggs on the they move through the intestines, The female common bot fly, hairs of the lips. The larvae hatch in 2 and pass out with the droppings. Gasterophilus intestinalis, lays yel- to 4 days and penetrate the inner lip They will then burrow into the low-white eggs on the hairs of the membranes in front of the incisors. ground where they remain for 1 to horse’s forelegs, chest, neck, belly, After 5 to 6 weeks, they migrate and 2 months. Adult flies develop within and sometimes on the hind legs and attach themselves to the stomach wall. the pupal cases and emerge dur- flanks (Figure 7). The eggs incubate Full-grown horse bots are thick, ing warm summer months. The life in 1 to 2 weeks and hatch only if tough-skinned maggots, blunt at the cycle from egg to adult fly takes 1 they are licked or eaten. Young bot posterior end and tapering in front year. larvae begin their migration in the to the two strong mouth hooks. mouth of the horse. They burrow They have a circle of prominent Controlling Bots into the front of the tongue and 3 spines around each body segment, The effective control of bots de- to 4 weeks later emerge out of the giving them a screw-like appearance pends on the treatment of the horse rear of the tongue before migrating (Figure 6). or the interruption of the bot’s life and attaching to the stomachARCHIVE wall They can become so numerous cycle by other means. (Table 1) G. (Figure 8). that they block the stomach outlet, intestinalis eggs accumulate until The female throat bot fly, G. resulting in colic. This blockage may frost but can survive for several nasalis, lays her eggs on the hairs also cause rupture of the stomach months. Egg cases are difficult to under the jaw and throat. Incubation takes 4 to 6 days and the larvae Table 1. Treatment for Bot Control hatch without stimulation. This pest Trade Name Active Ingredient Method of Administration penetrates the gum margins around EgValan, Zimecterin Ivermectin oral paste the cheek teeth for 1 month before migrating to the stomach, pylorus, Quest Melbemycin oral gel

Managing Insect Pests of Horses remove from the hair coat, but Controlling Horse Flies batch and each female can lay up to infective larvae can be lured from and Deer Flies 20 batches. Large populations build cases by sponging with warm (104° up when conditions are good. They to 118°F) water. Sponging horses on The control of horse flies and may become a serious problem cool days (below 60°F) will ensure deer flies is very difficult. They are early in the spring, and outbreaks that larvae quickly die of exposure. large, robust insects that are able to can occur in mid-winter during take a blood meal quickly, before Warm water can be applied with several weeks of warm weather. insecticides used for their control an insecticide if the treatment is become effective. Some of the syn- done on a warm day. The number thetic pyrethroid insecticides are of hatched G. intestinalis larvae repellent, and other insecticides that reaching the stomach can be include repellents give limited con- b reduced by treating the areas where trol of these pests (Table 2). bot flies glue their eggs. These areas should be treated on a weekly basis, using insecticide wipes or sprays. Stable Flies a Stable flies, Stomoxys calcitrans, Horse Flies and are some of the most harmful flies that attack horses. They are about c Deer Flies the same size as the common house Horse flies, Tabanus sp., and fly (Figure 10), and both sexes feed deer flies, Chrysops sp., are serious on blood. pests of horses. These heavy-bodied, Stable flies are usually found brown, black, or yellow flies are feeding on the lower legs or flanks strong fliers and vicious biters. They of the horse. Their bite is very pain- may fly 15 to 20 miles for a blood ful and causes horses to stamp and meal or to deposit eggs. Depending kick. When present in large num- 1 3 on the species, they are from ⁄ to bers, stable flies can cause blood d e 1 1 ⁄2 inches long and have clear or loss as well as severe irritation. They striped wings (Figure 9). stay on the animal only while feed- These insects feed by piercing the ing. After feeding, they seek a shel- Figure 9. Black horse fly, Tabanus atratus: (a) larva; (b) pupa; (c) adult. Deer flies skin of the horse with cutting mouth- tered area in which to digest their (Chrysops sp., d & e), irritate horses. parts and then drinking the blood meal. as it wells up from the wound. Only Stable flies are strong flyers and the adult females are blood feed- may fly several miles for a blood ers, and they feed only during the meal. The control of breeding sites daylight hours. Horse flies and deer may require a community-wide effort. flies can be found feeding on the b Stable flies breed in decaying a head, neck, legs, shoulders, and back. organic matter. A fermenting mix- Horse flies have been blamed for the ture of straw, manure, and urine is transmission of swamp fever (equine ideal for breeding. Although horse infectious anemia) in horses. manure is usually too dry to support Most horse flies and deer flies their development, it becomes a good have only one generation per year. breeding ground when it accumulates The female lays her eggs on vegeta- in stalls or barns where it becomes c d tion around moist, swampy places. moistened with urine or water. Round The larvae burrow into the mud after bale cattle feeding areas breed very hatching and spend the next year large populations of stable flies. feeding on small animalsARCHIVE such as Decaying straw, grass clippings, hay, earthworms, insects, small crustacea, and silage are also suitable breeding and even other horse fly larvae. They materials for stable flies. Figure 10. (a) Stable fly, Stomoxys calcitrans; pupate in the spring and emerge as (b) adult larva; (c) puparium; and (d) side view The life cycle of stable flies is 21 of the head detailing the mouthparts adults during the summer. to 25 days. Females must have a blood meal each time they lay eggs. They lay from 40 to 80 eggs per

Alabama Cooperative Extension System Table 2. Insecticides For External Parasite Control Pest Insecticide & Trade Names How Applied b Biting flies Permethrin (Permectrin, Ectiban, Atroban) Spray, wipe-on, dust horse flies, deer Fenvalerate (Ectrin) Spray flies, stable flies, horn flies Pyrethrins, PBO Spray, wipe-on c Resmethrin (Super Shield Fly Repellant) Wipe-on Mosquitos, Permethrin (Permectrin, Ectiban, Atroban) Spray, wipe-on, dust a biting gnats Fenvalerate (Ectrin) Spray (black flies, buffalo gnats, Coumaphos (Co-ral) Spray, dust punkies) Resmethrin (Super Shield Fly Repellant) Wipe-on Face flies Permethrin (Permectrin, Ectiban, Atroban) Spray, dust, wipe- on, strip Fenvalerate (Ectrin) Spray, treated strip Figure 11. House fly, Musca domestica, (a) on collar puparium; (b) adult; and (c) larva Pyrethrins, PBO Spray, rub-on Resmethrin (Super Shield Fly Repellant) Wipe-on Controlling House Flies Ticks Permethrin (Permectrin, Ectiban, Atroban) Spray, dust, or and Stable Flies wipe-on House flies and stable flies have Fenvalerate (Ectrin) Spray three requirements for the successful Coumaphos (Co-ral) Spray completion of their life cycles— Lice Permethrin (Permectrin, Ectiban, Atroban) Spray appropriate breeding materials, adequate moisture, and adequate Fenvalerate (Ectrin) Spray warmth. Coumaphos (Co-ral) Spray The elimination of any one of these three factors will prevent fly breeding. A successful house fly and Controlling Stable Flies House Flies stable fly control program should, Some insecticides are repellent therefore, include the following House flies, Musca domestica, elements: and can be effective for the control of are not serious parasites of horses, stable flies on horses (Table 2). These but they often build troublesome Elimination of Breeding materials should be applied gener- populations around horse barns, Materials. Good sanitation is the ously to the legs of the horse. They and they also carry diseases. These key to any successful house fly control program. In most cases, removal should be reapplied when they begin flies are about 1⁄4 inch long and dull to lose their effectiveness. black or dark gray in color (Figure of breeding materials is the most The best method for control- 11). House flies will use their spong- effective way to break the life cycle. ling stable flies off the animal is by ing mouthparts to feed on liquids Corrals, run-in sheds, and barns spraying the barn walls, posts, and associated with all manner of filth, should be designed to allow for the overhead. Nearby fences should also animal feeds, and human foods. rapid and efficient removal of be sprayed. Equally important is House flies breed in a wide vari- manure and other fly-breeding the removal of breeding sites where ety of rotting organic matter includ- materials. Feed mangers should be possible. ing garbage, all types of excrement, built to minimize feed waste and to Since stable flies and house flies wet and rotting hay, grass, straw, prevent manure and wasted feed have similar resting habitsARCHIVE and are grain, or silage. But house flies seem from collecting beneath them. Fly- found in some of the same breeding to prefer horse manure. They have a breeding materials should be sites, their control off the animal is short life cycle, taking from 6 to 14 removed and disposed of at least discussed with house fly control. days to complete development, and once a week to break the life cycle. they can build very high populations Sanitation should be thorough around stables if not controlled. if fly breeding is to be controlled. Areas missed when cleaning up with front end loaders or scrapers are usually prime areas for fly breeding.

Managing Insect Pests of Horses Breeding materials missed in these areas can produce many flies. Areas commonly missed in cleanup include those around fence posts, outside and under fences, outside and under feed troughs or hay racks, corners in barns or other buildings, stalls and sick pens, around silos or other feed storage areas, garbage cans, and around waterers and water tanks. Manure and other fly breeding materials are most easily disposed of by spreading them thinly on cropland. A flail-type manure spreader Figure 12. Spreading manure discourages fly larvae development. will ensure that the manure is ments in fly control, but they are 6 weeks (Table 3). Residual insecti- broken up into small pieces so that seldom completely successful. cides should be applied early in the it will dry rapidly and kill develop- Insecticides are usually needed to spring when the first flies appear ing fly larvae (Figure 12). Storage round out a complete fly control and should be reapplied whenever facilities should be available when it program; however, insecticides flies are no longer being killed. is not possible to spread the manure should never be the only means of Insecticidal space sprays, on fields. Manure stored in liquid control. fogs, and mists are used to con- manure pits or manure lagoons trol large numbers of adult flies, should be mixed with enough water Residual insecticides applied to the walls, ceilings, and rafters of especially in enclosed areas such as to discourage fly breeding. Agitating barns. These chemicals have a short the manure-water mixture will elimi- horse barns, run-in sheds, and vegetation such as hedges or windbreaks residual effect and must be applied nate the accumulation of floating on a daily basis (Table 3). solids where flies can breed. will control adult flies that use these locations as resting sites for up to Manure can also be stockpiled in non-liquid storage areas. Fly Table 3. Insecticides For Control Of Pests On Structures breeding is minimized by placing Pest Insecticide & Trade Names Remarks manure and other breeding House flies, Permethrin (Permectrin, Ectiban) Spray walls, ceilings, and materials in one area; however, flies stable flies Fenvalerate (Ectrin) fences where flies rest. can still develop in the outer few inches of stockpiled manure. Stored Stirofos + dichlorvos (Ra-vap) Spray ONLY. breeding materials should be spread Methomyl (Golden Maldrin) and other For house flies ONLY. thinly on cropland as soon as pos- commercial fly baits CAUTION: This sugar bait sible. Large amounts of composting is toxic to children and manure can reduce fly breeding domestic animals. problems and create a useful and Mosquitoes, Permethrin (Permectrin, Ectiban) Spray or fog mosquito and valuable by-product. gnats Fenvalerate (Ectrin) gnat resting areas, walls, Control of Moisture. Fly devel- ceilings, foundations. opment can be discouraged if ma- Spray ONLY outside of barn. nure and other fly breeding materials are kept dry. Corral areas should Stirofos + dirchlorvos (Ra-vap) Spray only. be designed to promote adequate Ticks Stirofos + dichlorvos (Ra-vap) Spray ground and low- drainage and to eliminate wet spots Permethrin (Permectrin, Ectiban) growing vegetation in where fly breeding is moreARCHIVE likely Fenvalerate (Ectrin) heavily infested areas to occur. Good drainage away from where animals rest. areas where manure is stockpiled Wasps Stirofos + dichlorvos (Ra-vap) Use on nests around will promote drying and also help barns, gates, etc. Drench reduce fly breeding. Automatic wa- nest after dark when terers should be properly adjusted wasps are quiet. and maintained to prevent leaking. Spiders Stirofos + dichlorvas (Ra-vap) Use in barns, tack rooms, Use of Insecticides. Sanitation stables, etc. Spray areas and moisture control are key ele- where spiders are found.

Alabama Cooperative Extension System Insecticidal baits are an ef- serious problem only in the north- Controlling Horn Flies fective supplementary means of ern third of the state. Horn flies are controlled on cattle controlling adult houseflies. Baits by using insecticide-treated ear tags, are available in dry or wet formula- Controlling Face Flies forced-use dustbags, or regular tions and should be spread in areas Face fly control is difficult. First, sprays. Some of these methods can where flies gather. Baits should be these flies feed on the animal’s head also be used for horses. The best used daily to maximize fly control where it is difficult to apply insec- control for horses is to prevent horn capabilities. Be careful to keep baits ticide. Second, face flies are strong flies from infesting cattle. Sprays and away from children and domestic flyers and may fly several miles to wipes help provide control on horses. animals (Table 3). infest horses and only stay on the Larvicides can be applied to animal for a short time each day. Biting Gnats areas of intense larval development They spend the remainder of their to kill the larvae before they become time on vegetation, fence posts, or Other blood-sucking flies that adults. Larvicides can also be use- other objects. often attack horses are biting gnats ful for controlling larvae in manure The use of spray or wipe-on (sand flies, buffalo gnats, punkies, stockpiles. insecticides applied to the head or black flies), which belong to the It is important to read and fol- neck of the horse is the most ef- Simuliidae family and are repre- low directions and to observe fective way to control these pests sented by many different species. proper safety precautions whenever (Table 2). Insecticide-treated strips using any insecticide. It is especially and collars are labeled for face fly important to avoid contaminating control on horses and are effective feed, water, and equipment. for 60 to 70 days. Wounds should be Mechanical Control. More tradi- protected with dressings or repel- tional methods of fly control should lents. Fly shakes attached to the hal- not be ignored when beginning a fly ter provide protection for the eyes. control program. Screening is an The use of dustbags or face rubbers excellent way to keep flies out and insecticide-treated ear tags on of areas such as feed rooms, tack cattle are useful and help to reduce rooms, and box stalls. Fans directing the overall population. an air blast downward and outward above doors will help prevent flies from entering barns. Horn Flies Horn flies, Haematobia irritans, are blood-sucking pests and are a Face Flies major pest to cattle. Horn flies will Face flies, Musca autumnalis, also attack horses if they are pas- are occasional pests of horses, espe- tured or ridden near infested cattle. cially when the horses are pastured Figure 13. Face flies are irritating eye pests Horn flies are gray to black in on horses. with or near cattle. These flies have color and resemble the housefly but sponging mouthparts, and both are about half as large. They com- the males and females feed on the monly hang upside down when mucous secretions of the eyes and feeding and are usually found on b nostrils as well as on blood oozing the backs, sides, and bellies of cattle d from wounds caused by horse flies and horses. They remain on the host or stable flies. Their feeding around animal day and night, leaving only a the eyes causes eye irritation (Figure to transfer to other animals or to lay 13). The face fly has sponging eggs (Figure 14). mouthparts with a toothed area that ARCHIVEHorn flies breed in fresh cattle causes irritation and tearing. c manure. Eggs hatch in less than 24 Face flies are about the same size hours and require moisture for sur- and color as houseflies. The female vival. The life cycle may be as short lays from 30 to 230 eggs in very as 10 days in hot weather and up to fresh cattle manure. The entire life 1 month in the spring and fall. This cycle takes from 15 to 25 days. Face species is not known to transmit any flies are found only in the northern horse diseases. Figure 14. Horn flies are sometimes found half of Alabama and usually are a feeding on horses. (a) adult fly; (b) puparium; (c) egg; and (d) larva

Managing Insect Pests of Horses Another closely related group of bit- are irritating to the animals, and portions of the body. These eggs ing gnats are the Culicoides (called large numbers of mosquitoes can hatch in less than 1 week. Larvae no-see-ums because they are so take large amounts of blood. They penetrate the skin and begin mi- small). are also the carriers of several of the grating through connective tissue. Some species of biting gnats feed encephalitides that are transmitted to Larvae of H. lineatum congregate in on blood in large numbers on the horses and humans. These diseases the esophageal tissue after 5 months inside of horses’ ears while others are usually fatal to horses. of wandering and remain there for 3 feed on the legs, head, neck, or months. belly. Large numbers are often Controlling Mosquitoes found feeding on horses. All Mosquito control is most effec- species breed in moist or running tive as a community wide project. a b water habitats. Eliminating breeding sites is one of the best ways of controlling mosqui- Controlling Biting Gnats toes. The regular use of insecticide Biting gnats are difficult to con- sprays or wipe-ons are effective on trol because they are strong fliers horses (Table 2). The space sprays, and are able to fly as far as 10 miles fogs, and insecticide strips used for for a blood meal. Also, they breed in fly control in stables also provide many different types of watery habi- good mosquito control inside struc- tats, from swiftly running streams to tures (Table 3). tree holes or mud. Insecticides that are repellent or Figure 16. Adult cattle grub flies: (a) the combinations of repellents and Eggs heel fly or common cattle grub; (b) the bomb insecticides are the most effective fly or northern cattle grub treatment when applied to the Hypoderma bovis larvae tend to animal’s body (Table 2 and Table 3). gather in the area around the spinal The synthetic pyrethoid insecticides Adult canal. Finally, larvae of both spe- have good residual action and are Larva cies migrate to the tissue under the repellent to most insects. When used skin of the back where they cut at close intervals (5 to 7 days), these Pupa breathing holes into the hide. They insecticides are effective as a direct grow rapidly and eventually create application for several species of a large, pus-filled cavity under the flies as well as gnats and hide. When mature, they widen the mosquitoes. breathing holes to escape, fall to Figure 15. Mosquito life cycle the ground, and pupate. During the Mosquitoes first warm days of spring, adult flies Several different species of mos- Cattle Grubs emerge, mate, and are ready to lay quitoes will feed on horses. Mosqui- Two species of cattle grubs will eggs immediately (Figure 17). There toes are slender-bodied, long-legged parasitize horses if they are pastured is one generation per year. flies that can be as large as 1⁄2 inch near cattle. Cattle are the normal Cattle grubs are on the wrong long. They have delicate wings and host for cattle grubs. These large, host when they parasitize a horse under the right conditions can build hairy flies resemble honey bees in and are not able to complete devel- large populations. size (1⁄2 to 3⁄4 inch) and appearance. opment. They make uncharacteristic Mosquitoes breed in standing or Bomb flies, Hypoderma bovis, are migrations to the head, neck, with- slow-moving water. They also breed banded with yellow and black strips ers, and rib cage areas. They remain in water in cans, bird baths, old rub- while heel flies, Hypoderma linea- just under the skin and form hard ber tires, or clogged gutters.ARCHIVE They tum, are smaller and more orange bumps that may become sores if have a short life cycle—10 days to 2 than yellow (Figure 16). the horse or the saddle rubs the af- weeks (Figure 15). Adult cattle grubs are prevalent fected part. They may be surgically removed by a veterinarian. Only female mosquitoes feed on during March, April, and May. Adults blood. They require one or more do not bite or sting, but animals blood meals for egg development. are frightened by the buzzing The males are mostly nectar-feeders. sound they make during egg laying. Large populations of mosquitoes Females deposit their eggs on the can be damaging to horses. Bites hair of the animal’s legs and lower

Alabama Cooperative Extension System protection of a heavy hair coat and drier skin. The entire life cycle is 1st Nymph 2nd Nymph spent on the horse (Figure 18). There are two very different spe- a cies of lice that are occasionally a problem on horses. One species, the horse-biting louse, Bovicola equi, is about 1⁄10 inch long. These lice are chestnut brown except for the abdo- b mens, which are yellow with dark Egg crossbands. They are very flat with broad, rounded heads and slender 3rd Nymph legs (Figure 19). These pests have chewing mouthparts and feed on dry skin, skin se- Adult cretions, and hair. Eggs are glued to the hair close to the skin, especially Figure 18. Horse louse life cycle around the angle of the jaw and on c the flanks. The eggs hatch in 5 to 10 days. Nymphs begin feeding im- Figure 17. Cattle grubs: (a) eggs of the heel mediately, reaching maturity in 3 to fly are often laid in a row on the hairs; (b) 4 weeks. eggs of the bomb fly, are usually laid one to a hair; (c) larva in last instar in the tumor The other species, a blood-suck- beneath skin of back ing louse, Haematopinus asini, is about 1⁄8 inch long and is a dirty gray color. These lice have very broad abdomens that contrast with their long, narrow heads. Sucking Controlling Cattle Grubs lice are more common, as well as The control of grubs in horses is more irritating, than biting lice. They best achieved by controlling them in have piercing, sucking mouthparts cattle. This reduces the total cattle and, when present in large numbers, grub adult population. The wide- can cause the horse to become ane- spread use of currently labeled med- mic. They are also very irritating and ications for internal parasite control cause the horse to rub excessively, in cattle has greatly reduced cattle often rubbing off patches of hair Figure 19. Horse-biting louse grub populations. Treatment with (Figure 20). systemic organophosphorus insecti- Eggs are glued to the hair and cides applied as a pour-on, spot-on, hatch 11 to 20 days later. The newly injectable, or spray is also effective emerged nymphs begin to suck for cattle. Control should be applied blood immediately. They complete soon after the fly season is over development in 2 to 4 weeks. (June in Alabama) but may also be This species is host-specific, made until the end of October. transferring from one horse to another during close contact. Some Lice animals are particularly susceptible to louse infestation and are known Signs of lice include scurfyARCHIVE skin, as carriers. They should be routinely an unkempt coat, and excessive inspected and treated if infested. rubbing and scratching. Lice can be found on all body regions but are usually noticed first on the head, neck, mane, and tail because of the horse’s self-grooming. Lice re- produce all year but are more of a problem during winter under the

Managing Insect Pests of Horses Controlling Lice horses’ ears, causing soreness and making it difficult to halter or bridle Proper grooming and feeding are the animals. Ticks can be controlled important elements of lice control. on horses with insecticides (Table 2). Grooming does not remove or kill lice, but it does give the horse’s owner the opportunity to spot the Using Insecticides problem early before it becomes When using an insecticide, care- harmful to the animal. Proper nu- fully follow the label directions. If trition allows the animal to better these directions are not clear, con- withstand the blood loss or irritation tact someone who can better under- of a severe louse infestation. stand them. The chemicals in Table Insecticidal sprays are effective in 2 and Table 3 are those labeled for controlling lice (Table 2). Wettable use on horses or in stables. They are powder (WP) formulations are gen- the best suited for the applications erally preferred over emulsifiable recommended. There may be others concentrates (EC), because some not listed that are also effective. horses are more sensitive to skin NOTE—The instructions for the burns from solvents in EC formula- use of the recommended pesticides tions. Problems should not occur if are not complete and are intended the insecticide is labeled for use on to be used as guidelines. Before horses for lice and if it is used ac- using any pesticide, read the label cording to the label directions. for more specific instructions. Many insecticides are sold under brand Ticks names not listed in this publication. Check labels for the names of rec- Ticks are generally a major ommended active ingredients. problem on horses only in heavily infested wooded pastures. However, in the spring, large numbers of several species of ticks may be found infesting horses and cattle. Ticks are blood-sucking arthropods closely related to insects. When present in large numbers, ticks can withdraw much blood and cause anemia in the animal. Also, ticks often infest ARCHIVE

Figure 20. Horse-sucking lice cause horses to rub off patches of hair.

10 Alabama Cooperative Extension System ARCHIVE

Managing Insect Pests of Horses 11 Gene R. Strother, Extension Entomologist, Professor Emeritus, Entomology and Plant Pathology, Auburn University. Appreciation is expressed to C. M. Christensen, Ph.D., Extension Entomologist, University of Kentucky, Lexington, and E. C. Loomis, Ph.D., Extension Parasitologist, University of California, Davis, for information and illustrations used in this publication. ARCHIVETrade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar. For more information, call your county Extension office. Look in your telephone directory under your county’s name to find the number. Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability. ANR-464 2M, Revised June 2007, Anr-464 © 2007 by the Alabama Cooperative Extension System. All rights reserved.