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Home , Habronema muscae, Housefly, Mosquito

Some Pests of Horses and Mules

BY F. C. BISHOPP ^

HERE IS condensed and practical information about several enemies of the horse and mule, including mos- quitoes^ sand (punkies), , horseflies, deer flies, buffalo gnats (blackflies), , lice, and . Special attention is given to control measures.

A CONSIDERABLE KUMiiER of iiisccts and inscct relatives attack equines in addition to the horse bots, stableflies, ticks^ screwworms, and discussed in other articles in this book. Some of them, such as the and sucking lice of horses and mules, are specific; some, like the tropical horse , attack other but prefer to feed on equines; and many others feed on various warm-blooded animals with- out seeming to prefer any one kind. A number of such pests at times become so abundant locally as to have serious effects on horses, causing poor condition, lower work output, difliculty in handling, and even death.

MOSQUITOES AND SAND FLIES Many kinds of mosquitoes and sand flies, or punkies, attack horses and nmles. As a rule, a moderate number of these do not greatly annoy horses; but the presence of large numbers sometimes constitutes a serious problem, especially amon^ high-strung animals such as race horses. Difficulties due to these insects have been en- countered at meets and fairs held during the late spring and early fall in cities along the south Atlantic coast. Screening the stables gives some protection against mosquitoes. Sand flies, however, readily pass through ordinary screens, and smudges and sprays are resorted to for relief from them. Painting the screens in the evening with a mixture of 1 part pyrethrnm extract 1 F. C. Bishopp i« Assistant Chief, Bureau of Entomology and Plant Quarantine. .492 Some Insect Pests of Horses and Mules 493 concentrate and 20 parts lubricating oil (S. A. E. 5), together with the use of a pyrethrum-kerosene spray in the buildings, is effective.^ Pasturing the horses on high ground free from dense woods and underbrush reduces the mosquito and sand hazards outdoors. Eliminating stagnant water in and near pastures, emptying and cleaning water troughs frequently, and, in areas, ditch- ing the parts of the marsh known to produce mosquitoes are effective steps in preventing trouble. Since there are many of mos- quitoes and they have widely divergent habits, control measures must be modified to fit the situation. After stagnant water has been elimi- nated as far as practicable, the principal lines of attack are: (1) Apply No. 2 fuel oil lightly to the surface pools where mosquito wig- glers are found; (2) keep livestock on high, open pastures when mosquitoes are abundant; (3) keep valuable animals in screened barns; (4) use kerosene-pyrethrum sprays to kill the mosquitoes on animals and in the barns; and (5) make smudges in which stock may find' protection during severe mosquito outbreaks. In this brief account it is not possible to discuss all the different methods of controlling mosquitoes. The reader is therefore referred to other published articles that supply more details (i, 4? '^)-^ The fact should not be lost sight of that at least eight American species of mosquitoes have been shown to be capable of carrying equine encephalomyelitis. Epizootics, or severe outbreaks, of this are usually concurrent with mosquito outbreaks, and pro- tecting animals f nom mosquito attack appears to be of some value in preventing the disease. THE The housefly is not of great importance as an enemy of the horse, but, if not controlled, it breeds in tremendous numbers in horse manure. The presence of this insect in abundance is a serious hazard to health. The housefly annoys horses by its persistent efforts to feed on body secretions, particularly those of the eyes. This leads to the suspicion that the flies may transmit certain infectious eye . The house- fly is an intermediate and transmitter of the roundworm para- site of equines, muscae (8), and it has also been shown to be capable, of. transmitting mastitis of cattle. The control of houseflies depends on the proper disposal of manure and vegetable refuse (S). Scattering such materials thinly over fields soon to be plowed is the most satisfactory method of handling them. Manure may be stored in fly-tight manure pits or on racks over water. Treating manure with borax at the rate of 11 ounces to each 8 bushels also checks fly breeding. If the manure is to be used as a fertilizer, borax should not be used in excess of this amount. Care should be exercised not to apply too large an amount of treated manure to soil, since applications heavier than 15 tons per acre are likely to injure some crops on certain soil types. 2 UNITED STATES BUREAU OF ENTOMOLOGY AND PLANT QUAEANïINE. SAND FLIES AND PUNKiEs. U. S. Bur. Ent. and Plant Quar. Cîr. E-441, 3 pp. 1938. [Processed.] = Italic numbers in parentheses refer to Literature Cited, p. 499. 494 Yearbook of Agriculture, 1942 Tlic use of properly bnitod fly trii])s as well as of keroseiie- pyrethruin fly sprays is an important siipplomontal control measure. Instructions for makino; a tlioroujihly practical fly trap will be fonnd in Farmers" Bulletin 734. Flytraps and Their Operation. HORSEFLIES AND DEERFLIES The -sucking insects known as Iiorsetlics and deer flies are often very troublesome to horses. Their bites are painful, and when the insects are numerous, they draw considerable blood. They also act as carriers of , the Asiatic disease surra, and possibly other equine maladies. There are many kinds of horseflies and deer flies of various sizes and colors (fig. 1). Some are relatively small, not more than half an inch in length, while otiicrs are three times that size and very lobust. These pests are widely distributed in this coun- trj\ being found in greatest numbers in marshy or swampy areas and along streams, where they breed. The are laid on plants FiCURE 1.- -A species of horselly. Three times iialiiral growing in or over the size. water or on stones in . . streams. xVfter hatch- ing, the larvae drop into the water and buirow into the imid or gravel, wiiere they feed on small, soft-bodied animals. After nearly a they pupate in the moist soil near the water, and soon the adult in- sects emerge. The adults are strong, fast fliers and may be found several miles away from water, but they are usually more abundant near it. As the breeding habits suggest, control is very difficult. Draining swamps and seepage areas along streams, deepening and straighten- ing the edges of lakes and ponds, and preventing accumulations of waste irrigation water in low places in meadows tend to reduce the mimber of horseflies. Wlien these pests are abundant, animals in harness may be given some relief by the use of burlap coverings. Darkened sheds and smudges ofl'er some protection to livestock not being worked. Horse- flies are not easily rei)elled, and as the individual flies usually remain on the animals for only very short periods, fly sprays are of little -value. BUFFALO GNATS Buffalo gnats, or blackflies, are pests of nearly all warm-blooded animals, but certain species prefer certain hosts. They are small, Some Insect Pests of Horses and Mules 495 rather heavy-set, humpbacked flies, or gnats (fig, 2). The bites they inflict on human beings are often very irritating; when there are many bites, the face and arms may become swollen, and severe generalized symptoms may result. Livestock are greatly annoyed by the bites of these insects. In severe outbreaks of the southern buffalo gnat in the lower Mississippi Valley many mules die, cattle nnd liorses are reduced in flesh, milk flow is cut, and the coats of the animals become rough and unsightly. Buffalo gnats breed only in running water. The larvae attach themselves to sticks, logs, stones, and aquatic plants in the faster flowing parts of streams. Stones or dams over w^iich water is rush- ing are often literally covered with the larvae, which, when fuU- o'rown, are from one-third to one-half inch in length. The larvae usually require sev- eral months to develop; then they pupate in cornucopialike structures which they spin on rocks in the water. The gnats burst out of the skins and in some way reach the surface of the rough water and fly off. The adult females appear to require one or more meals of blood before eggs develop. These are laid in a gelatinous mass on stones or twigs at the water's surface or, as in the case of the southern buffalo gnat, are dropped singly on the water as the females di]) to the surface from the swarm of gnats dancing over it. Bradley (2) has found that the eggs of thé southern buffalo gnat sink to the bottom and do not hatch until the following FIGURE 2.—Adult buffalo s])ring when floods occur again. The eggs gnat, or blackfly. Much of most species hatch in a few days. enlarged. The southern buffalo gnat usually appears in swarms in the lower Mississippi Valley during the first warm period of late winter or early spring. If the floods are widespread and the weather continues warm, tremendous numbers of gnats emerge. After a few weeks the gnats disappear, sometimes very suddenly. The turkey gnat {EiisimuMmn méridionale)^ which usually appears later in the spring than does the southern buffalo gnat, attacks live- stock to a limited extent but is especially destructive to poultry. Preventing the breeding of the southern buffalo gnat is very dif- ficult. Controlling floodwaters by holding them within dikes re- duces the extent of breeding, and it is advisable to remove from streams logs, brush, and other obstructions to which the gnats can attach themselves. The removal of stones is sometimes practicable in more northerly streams where buffalo gnats breed. It-is also helpful to install a series of dams to still the w^ater where it normally ripples over stones. In small streams near horse-breeding farms or vacation resorts wliere gnats are troublesome, emulsified pyrethrum concentrate may be used to kill the larvae. This material is very destructive to fish 496 Yearbook of Agriculture^ 1942 and other desirable aquatic life and therefore should be used only by an experienced person. If fish are present, nets must be placed across the stream to prevent them from drifting downstream witli the treated water and thus beiiig killed. Smudges are commonly resorted to, especially in gnat areas in the South, and are helpful in protecting both livestock and human beings from severe attack. Horses, mules, and cattle may be protected to some extent by being kept on high, oj^en pastures as^ far from flooded streams as possible. Animals should be watched and removed to protected places promptly if a severe outbreak of gnats occurs, since tlie initial attack usually is the one that causes death. Immunizing animals by inoculating them with "gnat extract," made from crushed and filtered gnats, has been tried by George- vitch (S) with a species causing great losses in the Danube Valley. This method appears to have some promise, but ftirther experi- mental work is necessary to determine its true value. Many concoctions have been used as repellents to protect human beings and animals from gnats, but none is very satisfactory. One of those most coinnionly used on animals is crankcase oil with a little pine tar added. The difficulty most farmers experience with oils and greases is that after their contimied use animals often become overheated when worked in the sun, the hair being shed in l)atclies, and the skin sometimes being badly burned. In an efïort to avoid these ill effects Bradley conducted some tests of nonoily nuiterials and found the following formula to be promising as \\ protection against the southern buffalo gnat: Boil 1/2 pound of soap in 1 gallon of water and slowly add 6 ounces of pine-tar oil '(specific gravity 1.065) while stirring vigorously; add 1 pint of this mixture to 21^ gallons of water; mop the animals with it in the morning and spray them lightly several times during the way. Another repellent, developed by Schwardt (9)^ is made by emulsi- fying 3 quarts of cylinder oil with 1 pint of fish-oil soap. This stock emulsion is diluted with 1 gallon of water and mopped or sprayed on the animals.

FLEAS AND LICE Fleas, especially the human , sometimes worry mules and horses considerably. These insects breed in barns, and their attacks frequentl}^ become so severe as to prevent horses and mules from standing in the barn even while eating. Methods of dealing with the pests in barns are discussed in the article on fleas, page 1188 of this volume. Lice not infrequently become so numerous on horses and mules as to make them unthrifty and rough-coated. Of the three kinds of lice found on equines, the bloodsucking* species known as Haema- topinm asini is the most injurious. This louse is about one-eighth of an inch in length and has an elongate head (fig. 3). The other tw^o species, known as Trichodectes pilosus and T, parumpUosus^ have rounded heads and are usually yellowish or reddish brown. They Some Insect Pesis of Horses and Mules 497 liave biting mouth parts and feed on skin scales. Sometimes they become incredibly nnmerous and seriously irritate horses, causing tliem to rub against objects, and to kick and stamp. The species of lice mentioned confine their attacks to members of the iiorse and remain on the host continuously. Tiie young lice closely resemble the adults except that they are smaller and paler. When removed from the host animal, the sucking lice are shoi-t- lived. living a maximum of 3 days under natural conditions. The biting lice, if kept on bunches of hair, may live for 10 days, but the -j majority of them die in 3 to 6 days. The eggs, or nits, are firmly attached to the liorse's hair. The incubation period of the is about •2 weeks and that of the l)iting lice is somewhat shorter. The sucking louse reaches maturity and the female begins laying eggs 11 or 12 days after iiatching. Lice are particularly abundant during the winter, wiien may become very heavy before they are observed. Even when no con- trol steps are taken, the lice diminisii in numbers when the hair is shed in the spring. However, a few of the ))arasites remain on the animals. Usually in the mane and tail, through- out tlie summer, and from these the builds up again the next winter. FiGlHE 3.—Slicking loiisi' of the horse The presence of lice in large num- and donkey. Much enlarged. bers is usually made known when the animal begins to rub itself against objects. The top of the tail is often made nearly bare in this way, and patches of hair are rubbed from the neck, sh()ulder.s, and flanks. Lice may pass from one animal to another by direct contact or by being rubbed olí in corrals xn- barns. A lunnber of , if properly ajiplied, are effective in killing lice, but since none of them will destroy the eggs, it is nece.ssary to treat infested animals at least twice to delouse them entirely. The irregularity in the time lequired for eggs to hatch and for the lice to mature makes it difficult to set an exact period between dippings. Schwartz, Imes, ajul Wiight (10, p. 37) state that "experience has shown that two dippings with an interval of 14 to 16 days usually can be depended on to control both sucking and biting lice." TICKS Several kinds of ticks attack horses and mules. One, called the tropical horse tick {Dernwcentor nitens), prefers equines to other 498 Yearbook of Agriculture, 1912 animals. The others attack various kinds of domestic and wild animals. The tropical horse tick is found in the extreme soiithern part of Texas aiul in tropical America. It attaches it.self mainly in the ears of the animal but may be found in the foretop .and mane or elsewhere on the head and neck. Tlie Gulf coast tick, technically .1 ¡nhlyommamamilatxim^m the adult stage attaches itself in the outer ear. The lonp- beak of this tick makes a severe wound, and when a group of the ticks i>uncturc an ear it becomes inflamed, thick- r ened, and sore. Not infrequently screwworm flies are attracted to the infested ears, and their larvae burrow into the tissues. If the screwworms are killed in time the animal's life may be saved, but frequently cartilage is destroyed and the ears droop. When this occurs the animal is said to be got eh-eared. The spino.se ear tick {Ornttho- fhiros mepest, see the article on Cattle Tick Feyer, page 572. The American dog tick {Dermacentor vaiidhiUs) attaches it- self to horses and human beings as well as to dogs and many other species of animals. On well-groomed horses this tick becomes at- tached mainly in the mane and tail and on the fetlocks. The ticks cause much irritation but are not known to carry any equine dis- ease. (See the article on this tick as a pest of dogs, p. 1180.) A number of other species of ticks are important as pests of horses in certain localities, among them the black-legged tick {Ixodes ricinus scapularis)^ the Pacific coast tick {Dermacentor occid&ntalis) ^ the lone star tick {Amhlyomma ainericarmm)^ and the cayenne tick {A, cajennense). Control measures for ticks must be fitted to the habits of the par- ticular species. Horses infested wdth the ear tick and the Gulf coast tick may be freed of these pests by treating the ears with a mixture of 2 parts of pine tar and 1 part of cottonseed oil. In order to reach all the ear ticks, it is necessary to work the material into the ear or to break up the mass of ticks, as described by Imes (6). The liquid should not be allowed to run down the side of the face, as it may cause shedding of the hair. Applications every 2 to 4 weeks will usually keep either of these species under complete control. The same treatment is effective in controlling the tropical horse tick. Dipping in an arsenical solution, as mentioned on page 575 of this volume, is the most satisfactory w:^ay of destroying cattle ticks and other species that infest various parts of the animal other than the ears. The short period of engorgement and the general host rela- tions of such species as the cayenne tick, the lone star tick, and the black-legged tick make complete control by dipping impossible. The winter ticks are more resistant to arsenical dips than the cattle tick, and many of them survive dipping in the standard-strength arsenical solution. Two dippings at 14-day intervals in a solution containing 0.22 percent arsenic trioxide will destroy most of the ticks if the animal is not exposed to reinfestation. Mopping infested animals wdth a mixture of 2 ounces of finely ground derris containing 5 percent rotenone, 2 ounces of neutral soap, and 1 gallon of water would probably kill all the ticks with which the wash is brought in contact. This wash is also effective for the American dog tick. Clipping helps to keep ticks off saddle horses, and dusting derris or cube powder in the mane and fetlocks also helps to hold down infestations. LITERATURE CITED (1) BiSHOPP, F. C. 3939. DOMESTIC MOSQUITOES. Ü. S. Dept. Agr. Leaflet 186, 8 pp., Hlus. (2) BRADLEY, G. H. 3935. THE HATCHING OF EGGS OP THE SOUTHEKN BUFFALO GNAT. Scieuce 82: ?77-27a 500 Yearbook oj Agriculture, Í94¿

(8) GEOHGéVITçH. JIVOIN. 1923. NOUVELLES lUJOHKRCHKS SUB LA MOUCHE ÜF,GOL0URATZ. [Píiris] ACîKI des Sei. CoiiipL Rend. 176: 1500-1502. (4) HKRMS, WILLIAM BBODUKCK, and GRAY, HAROLD FAUNS WORTH, 1940. . ;il7 pp., iUus. New York. (5) HOWARD, L. O., and BISHOPP, F. C. 1026. THE HOUSK Fi-Y AND HOW TO SUPPRESS n\ U. S. Det>L Ajcr. Farmer.^' Bui. 140S, 17 pp.. ilhis. (Revised.) (6) I MES, MAKION. 19LS. THE Sl'INOSB EAR TICK. U. S. I>e[lt. AfTP. FaiUUTS' Bill. 980, 8 pp., illiis. (7) KING, W. V., BRADLKY, O. H., and M( XKKL, T. K. 1080. THE MOSQUITOES OF THK SOUTHEI-VHTKRN STATtiS. Ü. S. Dept A^V. Misc. Pub. 336, 91 pp., illus. (8) RANSOM, B. H. 1013. THE LIFE HISTORY OF HAITR<)NK^^A MUSCAE ( CARTER)» A PARASITE OF THE HORSE TRANSMIíTEI) KY THK HOUSE FF.Y. U. S- Bui'. A ni Ml. ludus. 163, 36 pp., illus. (9) SCHWARDT, H. H, 1935. LUBRICATING OIL EMLXSION AS A UUFFALO GNAT REl>ELfJí:NT. KaUS. Ent. Soc, Jour. 8; 141. (10) SCHWARTZ, BENJAMIN, IMES, MARION, and WRIGHT, W. W. 1930. PARASITES AND PARISITIC DISEASES OF HORSES. U. S. De[)t. Agi*. Cir. 148, 55 pp., illus. (Revised.)