Managing External Parasites of Texas Cattle

Introduction

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• Intro
• Integrated Pest Management
• Safety tips for using pesticides
• Livestock pests
• Insecticide application methods

Authors:

Sonja L. Swiger | Assistant Professor and Extension Entomologist

Texas A&M University System

Intro

The Texas dairy and beef cattle industry is a $12 billion industry and controlling external parasites is an important part of avoiding financial losses.

External parasites, commonly called ectoparasites, cost livestock owners billions of dollars each year. Untreated, these parasites make animals suffer and lose weight. Parasites also lower the quality of animal products by:

▶ feeding on their hides and hair

▶ reducing meat and milk production by sucking their blood

▶ transmitting diseases

▶ causing cattle to lose energy

Integrated pest management

Efficient pest management requires that cattle operators understand the three components of integrated pest management (IPM) and how they work together. IPM uses cultural, biological, and chemical control methods to more effectively suppress insect pests.

Cultural control

Cultural control focuses on preventing new infestations by minimizing conditions that support insect breeding.

The best way to prevent initial infestations is to check and treat new cattle for lice, ticks, or mites before adding them to existing herds.

Poor sanitary conditions in and around barns/operations encourage insect reproduction. The most effective way to control insect and mite populations, minimize breeding conditions:

▶ Remove and dispose of carcasses quickly.

▶ Clean up and dispose of manure and spilled feed—especially if they are wet.

▶ Keep drainage ditches clear by cleaning out weeds.

▶ Remove straw or hay that has been defecated and urinated on.

▶ Clean and dress all wounds on cattle to exclude blowflies and prevent infection.

One pound of moist manure or wasted feed can support the production of up to 1,000 house flies—but larvae cannot survive on manure with less than 30 percent moisture. Remove manure from barns at least twice a week and spread it thinly on pastures. Do not pile manure or leave it in clumps. Rotate the pastures to allow manure to dry out and decompose.

Biological control

You must identify insect populations accurately to make pest control decisions and avoid overusing pesticides. Some insects are harmless to humans and animals and can be used to control pest insects through predation:

▶ Fire ants prey on any available larvae.

▶ Black dump fly larvae feed on house fly larvae developing in the same manure.

▶ Small fish and immature dragonflies, damselflies, and mayflies feed on mosquito larvae.

Beneficial insects can also control pest populations through competition:

▶ Soldier fly maggots eat more manure than horn fly or housefly maggots, leaving competitors short of food and unable to complete development.

▶ Dung beetles remove manure to house their larvae. This causes the pats to dry faster and become unsuitable for fly development.

▶ Parasitic wasps lay eggs inside immature horn flies, house flies, and stable flies. The wasp larva then eats the immature flies.

Though wasps can be used to supplement sanitation, parasitic wasps probably will not control pests adequately in an environment that promotes breeding. For more information, see http://www.ca.uky.edu/entomology/entfacts/ef502.asp.

Chemical control

Pesticides should be used only when preventive methods are not effective or available. Use chemical control methods only when pest activity is at its highest.

Safety tips for using pesticides

▶ Follow all directions and safety precautions precisely. Never deviate from pesticide label recommendations.

▶ Record every pesticide application; include the common name, trade name, formulation, dilution, application rate, and date of treatment.

▶ Use a facemask or respirator and protective clothing during spraying. Avoid breathing spray mist or dust. Follow label recommendations regarding personal protective equipment.

▶ If you spill pesticides on your skin or clothes, wash them thoroughly with soap and water, and change clothes. Wash contaminated clothing separately from household laundry.

▶ Do not eat, drink, or smoke when handling pesticides.

▶ Provide adequate ventilation when applying pesticides.

▶ Follow label application rates to avoid illegal meat and milk residues and possible harm to the animal.

▶ Never apply pesticides closer to slaughter dates than the number of days listed on the label.

▶ Avoid wind drift; pesticides can kill fish, wildlife, and crops.

▶ Do not treat animals that are sick, overheated, or stressed from shipping, dehorning, castration, recent weaning, etc.

▶ Do not contaminate mangers, feed, water, milk, or milking equipment.

▶ Do not spread treated manure on pastures or cropland against label recommendations.

▶ Store pesticides in the original, labeled containers, safely locked away from children, pets, and livestock.

▶ Dispose of empty pesticide containers promptly and according to specified recommendations.

▶ If you suspect poisoning, call a doctor immediately. Symptoms include blurred vision, abdominal cramps, diarrhea, excessive salivating, vomiting, tremors, and tightness in the chest.

Livestock pests

Horn fly

Horn flies (Haematobia irritans) bite cattle and feed on their blood; they weaken the animal and make it lose weight.

Adult horn flies have piercing mouthparts and each fly feeds 30–40 times per day. The bites are painful and will form a wound that mars animal hides.

Horn fly populations increase from late spring to early fall; they peak in midsummer. They rest on the withers, back, and sides of the cattle, moving to the belly when temperatures exceed 90 degrees F. Cattle react by licking their backs, twitching their flanks, switching their tails, and kicking at their bellies with their hind legs. When flies exceed 250 per side, cattle will lose 15 to 50 percent of their weight.

Horn flies are the same color as house flies and stable flies but are slightly smaller (3/16 in.). The females can lay several hundred eggs in their 3-week lifespan. They lay their eggs under the edges of fresh dung pats where they develop in 10–20 days, depending on the temperature.

To control and prevent horn fly infestations:

▶ Kill adult flies before they harm the cattle or produce offspring.

▶ Exclude adult flies with screens or other barriers.

▶ Drag pastures and spread manure in a thin layer to limit breeding grounds.

▶ Rotate pastures to prevent manure buildup.

Beneficial organisms such as predators, parasitoids and natural competitors will help control insect populations. Predatory mites, beetles and the larvae of certain flies such as Hydrotaea spp. or Muscina spp. feed on horn fly larvae. Parasitoid wasps such as Muscidifurax spp. and Spalangia spp. feed on pupae. Dung beetles and the black soldier flies compete with horn flies for cattle dung.

The point at which chemical control measures are economically justified is called the threshold. For horn flies, the threshold is 250 flies per side. Use chemical control once the threshold is reached. Control options include:

▶ ear tags

▶ sprays

▶ pour-on liquids

▶ back rubs

▶ injections

▶ insect growth regulator

▶ mineral feed products

▶ boluses

▶ dust bags

Place self-treatment devices at bottlenecks near water, feed, or mineral sources. It may take 2 –3 weeks before cattle adopt self-treatment devices. Forcing cattle to use these devices can help control lice and will control horn flies more rapidly.

Insecticide-impregnated ear tags can also give excellent control if they are properly attached and the insect is not insecticide-resistant. The tag applies a small amount of insecticide to the animal’s body over a 2½- to 5-month period. Replace the tag when the insecticide is depleted and no longer controls the flies. Ear tags are an economical way to control horn flies, Gulf Cost ticks, and spinose ear ticks.

Managing pyrethroid- and organophosphate-resistant horn flies

Alternate the type of active ingredients to avoid or minimize insecticide resistance. Treating successive generations of flies with the same types of insecticides promotes insecticide resistance; insects that are susceptible to the active ingredient are quickly killed; those that are not passed on their genes and increase the number of resistant insects.

Horn fly resistance to organophosphates was first recorded in the 1970s; resistance to pyrethroids was confirmed in 1984.

Flies that resist one pyrethroid will resist all other pyrethroid insecticides currently labeled for use in Texas. To reduce resistance, delay treatment until flies reach threshold levels and susceptible flies mate with resistant ones. Periodic application methods (sprays, self-treatment devices, etc.) tend to delay development of resistance more than do continuous release meth-ods such as ear tags.

Treatment options

▶ Use sprays, dusts, or other formulations with a different mode of action than the ear tag, and treat only when horn fly populations exceed 250 per head.

▶ Alternate the type of ear tag insecticide each year. Organophosphate (OP) ear tags such as Terminator II, OPtimizer, Patriot, Warrior, or Dominator can be used after a pyrethroid ear tag. Do not use organophosphate ear tags for more than 2 successive years. Organochlorine (Avenger) or macrocyclic lactone (XP 820) ear tags are effective alternatives to pyrethroid or organophosphate ear tags.

▶ Remove the ear tags when calves are weaned or when the cows are worked in the fall. If there are more than 200 to 250 horn flies per head when the tags are removed, use a spray or dust with a different mode of action to reduce overwintering flies.

Combination ear tags are not recommended be-cause they combine modes of action and can promote resistance to both classes of insecticides at the same time.

Housefly

The house fly (Musca domestica) is the most abundant insect of confined cattle. This fly breeds continuously in manure and rotting vegetation. Adult house flies are about ¼ in. long and are gray and black with four black stripes on the thorax. The sides of the abdomen are creamy yellow and distinctly noticeable.

House flies do not bite; they feed on blood, sweat, tears, saliva, and other bodily fluids. Cattle respond by flapping their ears, shaking their heads, and avoiding infested areas. House flies can infest cattle wounds with maggots and spread pathogens (disease-causing organisms) such as E. coli.

Sprays, baits, light traps, and adhesive strips can control adult flies in livestock barns. Although, insecticides can keep maggots from developing on manure piles, chemicals alone will not solve the problem. Do not contaminate feed, utensils, or drinking water with insecticides.

Spread manure so heat and drying can kill eggs and larvae. Remove waste and spilled feed regularly.

Stable fly

Stable flies (Stomoxys calcitrans)are the US cattle industry’s most costly pest. They look like houseflies but are smaller (3/16 in.) and inflict a painful bite. Unlike horn flies that remain on the animal, stable flies rest on nearby surfaces after feeding.

Although stable flies suck blood only once a day, their irritation inhibits weight gain and milk production. They attack the legs, sides, back, and belly; cattle will stamp, and kick, and switch their tails. They will also bunch in a group, which keeps them from dissipating excess heat when it is hot and humid.

Stable flies congregate near confined animals indoors or out and breed in mixtures of urine, manure and decaying litter. Larvae (maggots) develop in straw bedding, wet hay, and manure accumulations. Eggs develop into adult flies in 3 to 4 weeks; adults can live for 3 weeks.

Stable flies begin to cause economic losses and must be controlled when concentrations reach two to four flies per leg.

Dispose of manure and litter as outlined for house flies to help reduce populations. Discard tram-pled hay bales and place new ones in another location to reduce larvae development. Predators, parasites, and pathogens that attack horn flies will also help in managing stable flies. Spraying animals and resting areas with approved insecticides will control flies immediately.

Screwworm fly

The primary screwworm fly larvae feed on living tissue but have been eradicated from texas. The secondary screw-worm fly larvae, Cochliomyia macellaria, feed on dead tissue and are found throughout the continental United States. The female lays eggs only rarely in wounds on living cattle but often in the natural openings of fresh carcasses. The larvae begin to develop within 10 to 20 hours.

There is always a danger that screwworm-infested animals could be reintroduced into uninfested areas. Inspect livestock for screwworms and report any suspected screwworm cases to your county Extension agent or local veterinarian. Submit any suspect larvae found in animals for identification.

For identification, collect 10 larvae from deep within the wound and place them in alcohol. Send the samples to:

USDA–ARS–KBUSLIRL
Screwworm Research Unit
2700 Fredericksburg Road
Kerrville, TX 78028.

Or

National Veterinary Services Laboratory

Attn: Sample Processing Department 920 Dayton Ave
Ames, IA 50010 (515) 337-7266.

The US Department of Agriculture, Animal and Plant Health Inspection Service international services office at (301) 734-8892 also can provide assistance.

Myiasis

Myiasis is the invasion of a living vertebrate animal by fly larvae. Myiasis can be classified as accidental, facultative, or obligatory:

▶ Accidental myiasis occurs when an animal ingests food contaminated with fly eggs or larvae; the larvae typically are not parasitic but cause discomfort as they pass through.

▶ Facultative myiasis is not essential to the life cycle of the parasite, but occurs, for example, when the maggots of blowflies that normally feed on carrion invade an open sore on living cattle.

▶ Obligatory myiasis is the infestation by a fly species that require a living host for development. Examples are the primary screwworm and botflies.

Blow fly

Blowflies are big and metallic green and blue. They seek carrion for their larvae, though maggots are sometimes also found in cattle wounds. Black blow fly larvae often infest dehorning wounds during winter and occasionally infest the navels of newborn animals. Heavy infestations are occasionally fatal.

Blowflies breed and reproduce in decaying animal and bird carcasses, dog manure, and wet garbage. Remove dead animals to prevent heavy blowfly infestations. Clean infested wounds and treat them immediately with a topical pesticide until the larvae are gone.

Cattle grub (Heel fly)

Heel fly larvae are called cattle grubs; they reduce feed efficiency and lower milk production, weight gain, and hide value. They make cattle run wildly with their tails in the air (gadding) or stand in water to protect themselves. Affected animals have poorer carcass trim and lower meat quality.

Female flies lay eggs on the legs and lower bodies of cattle. Eggs attached to the hairs hatch into tiny larvae that penetrate the skin and migrate through the animal’s body. Larvae congregate in the tissues of the esophagus or spinal column, but eventually move to the back in later summer, fall, or winter. Grubs develop a “cyst” or “warble” in the animal just under the skin on the back. After 6 to 8 weeks, grubs cut holes in the hide, fall to the ground, and pupate. Adult heel flies emerge in late winter, spring, or summer.

Cattle grubs can be controlled once they reach the animal’s back; but by then, most of the damage is done. Prevention is preferable.

Systemic insecticide sprays, dips, pour-ons, boluses, and injectables are distributed through the animal’s body and destroy cattle grubs by contact. To avoid a host/parasite reaction, use systemic insecticides when heel fly activity ceases between May 1 and July 4 but not within six to 7 weeks before grubs appear on the back. Typical host/parasite reaction symptoms include:

▶ swollen esophagus

▶ bloat

▶ profuse salivation

▶ discomfort

▶ in extreme cases, death

Organophosphate poisoning symptoms are similar to host-parasite reactions. However, do not use the antidote for OP poisoning, atropine, because it may make the problem worse.

Other biting flies Horsefly and deer fly

Female horse flies and deer flies are vicious bit-ers and make livestock lose weight. They also can transmit anaplasmosis, anthrax, and other diseases. Horseflies are a serious nuisance to livestock and even a few can significantly reduce production. Most of these flies are found in damp, brushy, or low-lying areas near creeks, streams, or tanks.

The horse fly measures ½–1½ in. long: the deer fly is generally ¼ –1/3 in. long, and readily bites humans.

A female horse fly can lay up to 800 eggs at a time. Though most species lay eggs on vegetation near a water source, some lay their eggs in dry soil or leaf litter.

Female horse flies are not easily deterred or dislodged. Heavy attacks can reduce weight gain, milk yield, and feed utilization, and damage the hide.

Controlling these flies is difficult because one location can have several species that feed at different times. Spraying these flies while on the animal is ineffective because each fly generally feeds for only 4 minutes. No insecticides kill the larvae or pupae.

Moving livestock from infested areas may provide some relief, but shelter or barriers offer the most effective protection. Box traps and canopy traps can limit the number of adult flies in an area.

Biological controls such as ladybird beetles feed on the eggs; wading birds and dragonflies feed on the larvae. Some large solitary wasps attack the adults, and parasitoid wasps rear their young on various stages of horse flies and deer flies.

Mosquito

Mosquitoes multiply in water and attack mostly at dusk. Large populations can hinder production and, in some cases, even kill livestock and wildlife by sucking their blood and transmitting diseases.

Mosquito larvae develop in tidal pools, rain pools, or floodwater; in permanent surface water like pools, streams, swamps, and lakes; and in water-holding containers like tree holes, drinking water troughs, and discarded tires.

Female mosquitoes will lay eggs on water or on a surface where water will accumulate. Eggs generally take 2 to 3 days to become larvae but can take up to a week. Most mosquito larvae take 6 days to become a pupa, then 2 days to become an adult.

To control mosquitoes, eliminate standing water to prevent egg-laying and larval development.

Natural controls do not significantly reduce mosquito populations. Birds, bats, dragonflies, and fish eat mosquitoes but do not reduce their numbers significantly.

Chemical control is necessary for heavy infestations. Sprays reduce the number of biting females and some products treat standing water. Topical sprays repel biting mosquitoes. Ear tags, back rubbers, or dust bags will protect cattle against mosquito adults without further intervention, but you should monitor water sources for larvae.

Products containing Bacillus thuringiensis israelensis (Bti) and B. sphaericus kill larvae effectively.

Black fly

The black fly is a small humpbacked fly that can irritate and even kill livestock. Black flies depend on flowing water for their larvae and are found along fast-moving rivers, particularly in northeast Texas.

The female black fly lays eggs near a riverbed. The larvae attach themselves to vegetation and filter food from the water. Black fly adults can emerge from their Photo by J.V. Robinson pupal cases in such large numbers that they can suffocate cattle.

Black flies have a painful bite and can transmit diseases. Black fly swarms can make cattle crash into structures, stampede, and even trample calves.

These flies are best managed at the larval stage by treating the water where they grow. Treating cattle with dusts, ear tags, back rubbers, pour-ons and sprays will limit the number of black fly attacks. For additional protection, use shelter, smoldering fire, permethrin-based repellents and white petroleum jelly on the ears.

Lice

A single cow can harbor more than a million lice. Symptoms include lameness, dermatitis, hair loss, allergic responses, and skin crusting or scabbing. Lice cause anemia, lower milk production and inhibit feed efficiency and weight gain. They also lower the animal’s resistance and increase secondary diseases and mortality.

The cattle biting louse (Bovicola bovis) feed on hair and scales and prefers the top line of the animal’s back, especially the withers. It can spread to other parts in heavy infestations.

Four species of lice suck blood from cattle:

▶ The short nosed cattle louse (Haematopinus eurysternus)

▶ The longnosed cattle louse (Linognathus vituli), which occurs in greater numbers on calves than mature cattle; it can be found all over the body but prefers the shoulders, back, neck, and dewlap.

▶ The little blue cattle louse (Solenoptes capilla-tus), is the smallest of the lice and gets its name from its color at maturity. It is a common species on cattle and clusters on the face. These lice also infest the top of the neck, the dewlap, and the brisket. During heavy infestations, they can be found from the horns to the tail.

▶ The cattle tail louse (Haematopinus quadriper-tusus), populations peak during the summer. The adults are typically confined to the tail region; the nymphs will be found on the face, neck, vulva, and anus.

Lice spread in cattle by direct contact and can heavily infest animals that are sick, very young, or very old. Heavy infestations can be debilitating and cause restlessness and anemia. Sucking lice can also spread bovine anaplasmosis.

In temperate regions, lice are typically more abundant during winter and spring, so treat cattle in the late fall and early winter. Control methods include:

▶ spot treatments

▶ quarantine of infested individuals

▶ dust

▶ powders

▶ sprays

▶ dips

▶ ear tags

▶ boluses

▶ pour-ons

▶ lotions and

▶ injectables

Systemic pour-ons, injectables, and oral products are effective and popular treatments. Do not use systemic products on grub-infested animals in winter because reactions can be lethal.

Heavily-infested cattle are a major source of reinfestation for a herd. Cull these animals to protect the rest of the herd.

Mites

Mange mites tunnel into the skin and deposit their eggs inside. Scab mites deposit their eggs at the bases of hairs or in the skin. They initially irritate the skin and cause scabs that enlarge as feeding continues. Left untreated, they will fully occupy the skin or hair follicles. Problems include:

▶ persistent dermatitis

▶ mite-induced allergies

▶ transmission of microbes and metazoan parasites

▶ intermediate parasites (tapeworms)

▶ invasion of respiratory passages, ear canals, and internal organs

On stressed, pregnant or lactating cows, the cattle follicle mite (Demodex bovis) causes nodules under the skin that can be felt but not easily seen. Heavy infestations can cause lesions on the neck, shoulders, and udder and between the forelegs and body.

Nodules will form over a 1-month period, and then gradually disappear and be replaced by other nodules. The smallest sores are the size of a pinhead, the largest as big as a chicken egg. The nodules eventually rupture and exude a pus-like substance full of mites causing defects to the hides.

Scabies, psoroptic, and chorioptic mites (Sarcoptes scabiei, Psoroptes bovis, Chorioptes bovis) must be reported under state law. If you suspect these mites, contact the Texas Animal Health Commission, Box 12966, Austin, Texas 78711, 1 (800) 550-8242.

Scabies mites are spread by direct contact. The adult females burrow in the upper skin layers, where the mites live. Cattle react to fecal deposits in the burrows 3 weeks after scabies mites first infest. Lesions occur first in areas with thin hair (such as on the head) but quickly spread over the entire body and cause generalized mange. Progressive infestations make the skin thickens and crust; scratching and rubbing will cause secondary infections. Because mites are difficult to collect, infestations are usually diagnosed by clinical signs and positive responses to acaricide treatments.

The psoroptic scab mite causes mange that spreads rapidly by contact with another animal or indirectly from an infested object such as a fencepost or stall. These mites are more prevalent in the winter and feed by abrading the skin. The host responds by developing swelling and dermatitis around the blood vessels.

The chorioptic scab mite causes mange that is irritating and develops crusty lesions. Chorioptic scab mites feed primarily on the legs and feet and generally go unnoticed as cattle spread them. Cattle typically react to them only when infestation reaches into the thousands and mange develops. Chorioptic mange is also referred to as foot mange, leg mange, or itchy heel.

Reportable Diseases

Report any suspected foreign or emerging animal disease to the Texas Animal Health Commission immediately. Texas law requires that specific livestock and fowl diseases (a complete list can be found at http://info.sos.state.tx.us/fids/200904288-1.html) be reported to the TAHC within 24 hours of diagnosis. This requirement applies to veterinarians, veterinary diagnostic laboratories, and people who manage animals.

Ticks

Several tick species attack livestock. Ticks can spread protozoan, viral, bacterial, and fungal pathogens and also injure cattle by feeding on their blood. Tick damage to cowhides reduces their value.

Ticks are classified as hard or soft. A hard tick has a prominent plate on its back known as a scutum. This plate is hard and its color varies according to species. The mouthparts of hard ticks extend from the front of the head, and they feed only once between each stage of development. Female hard ticks also lay eggs only once.

Hard ticks differ according to the number of hosts they use during their lifecycle:

▶ A one-host tick stays on a single host from egg through adult; after the female’s final feeding, it drops from the host, lays eggs, and dies.

▶ A two-host tick completes the larval and nymphal stages on a smaller host such as a rabbit, then moves to a larger host such as a cow for the adult stages. After the adult female feeds, it drops from the host, lays eggs, and dies.

▶ The three-host tick begins as a larva on a small host such as a squirrel, where it takes a blood meal, and then moves to an intermediate host such as a rabbit. The nymph feeds once on the intermediate host and then detaches. The adult attaches to a large host such as a deer or a cow, where it feeds once, detaches, lays its eggs, and dies.

Soft ticks have no scutum and appear more rounded. The mouthparts are located beneath the body. Soft tick females can take multiple blood meals as adults and lay multiple batches of eggs.

Common Texas ticks

Texas cattle fever disease was eradicated in the US in the early 1900s. However, since 2009, Boophilus tick populations have reentered South Texas.

Two species of this tick, B. annulatus and B. microplus, spread the protozoans that cause Texas cattle fever. This disease causes animals to develop a high temperature, stop feeding, and become anemic. The animal will eventually become lethargic, lapse into a coma, and possibly die. Heavily infested cattle that do not develop cattle fever disease will still gain less weight and produce less milk.

The Texas Animal Health Commission and the USDA are working together to prevent Boophilus ticks from spreading beyond South Texas and the quarantine zone.

The Lone Star tick (Amblyomma americanum), is aggressive, will attach to many types of hosts, and transmits several pathogens. This Amblyomma americanum tick prefers wooded or brushy areas during spring and summer. It is most abundant in Central Texas and has killed white-tailed deer.

The Gulf Coast tick (Amblyomma maculatum) ranges from the Texas Gulf Coast to central Oklahoma. In Texas, populations peak in late summer and early fall. Adults attack cattle mainly around the ears, eyes, and poll. Heavy infestations can injure the skin and often render the hides useless.

The winter tick (Dermacentor albipictus), is a one-host tick that attacks during the winter and late fall. Heavy infestations of this tick cause blood loss that can lead to anemia or even death.

The black-legged tick (Ixodes scapularis), is prevalent in the eastern half of Texas during spring and winter. It is most commonly found on white-tailed deer and is the primary carrier of Lyme disease. The winter tick readily feeds on humans.

The spinose ear tick (Otobius megnini), though limited in Texas, often infest livestock and domestic and wild ruminants. The larvae and nymph stages feed on blood; the adult does not. These ticks attach deep within the ears and cause intense irritation, wax accumulation, and excretions that can lead to ear infections.

Pesticides known as acaricides are used commonly to prevent and control mite and tick infestations. Clearing or burning dense vegetation will also help reduce tick populations.

Insecticide application methods

Sprays

Prepare only enough solutions for the number of animals you plan to treat. Do not store mixed insecticides. Emulsifiable concentrates or soluble formulations are well suited for use in small sprayers. For wettable powders, sprayers should have a high-volume piston pump with a suitable agitator. Apply sprays at a pressure of 250 to 350 pounds per square inch.

For ticks, lice, and mites, use enough water to cover the animal thoroughly. When spraying system-ic insecticides to control cattle grubs, be sure to wet the animals to the skin.

Dips

Dip vats are effective and, when properly maintained, can be used several times a year. The initial cost is high, but many animals can be dipped during the season with little additional expense. Vat treatments ensure good coverage by wetting the animal thoroughly. Vats are the most effective way to treat for Boophilus ticks.

Follow label directions when filling or recharging a dipping vat; use only products labeled for dipping animals. Do not mix different products unless specified on their labels. Stir the vat thoroughly before dipping animals.

Pour-ons

Apply pour-on insecticides directly to the center of the backlines of animals. The chemical is absorbed and then circulates through the animal’s system. Backline pour-on treatments control horn flies for up to 30 days

Spot-ons

This method uses specially designed applicators to apply a small amount of pesticide to a single spot on the animal’s backline. Spot-on pesticides are best used for cattle grubs and lice.

Dusts

Dusts are applied with hand shakers or self-treatment dust bags. They are most valuable against horn flies and lice on large animals.

Injectables

Avermectin and milbemycin treatments for beef cattle are formulated for subcutaneous injection and are also labeled for internal parasite control.

Feed and mineral insecticide additives

Some insecticides may be administered as feed or mineral additives. These control specific fly species whose maggot stages develop in animal manure.

Insecticide-impregnated ear tags

Ear tags are plastic devices that dispense insecticide to control ear ticks and horn flies. They control ear ticks for 4 to 5 months and horn flies for 2½ to 5 months. Ear tags also help control most biting insects, such as stable flies, mosquitoes, and lice.

Baits

Baits help control house flies that congregate around feedlots, dairies, and livestock barns. Baits are made of dry sugar, syrup, or other substances that attract house flies. A small amount of insecticide is added to kill flies that eat the bait.

Boluses

Boluses are administered orally and slowly release chemicals in the animal’s second stomach. These chemicals pass out into the manure and disrupt the development of maggots.

Read and follow label directions

The Environmental Protection Agency establishes tolerances for pesticide residues in agricultural commodities intended for human consumption. Follow the manufacturer’s label recommendations label concerning safety restrictions, dosage, and application. Observe all label-specified withdrawal intervals to avoid illegal residues in meat or milk.