Pest Management Recommendations for Dairy Cattle

BIOLOGICAL CONTROL

Female flies lay their eggs on manure, calf bedding, wet feed, or silage. The larvae hatch, and the maggots develop for about a week before they reach the pupal stage. Inside the pupa, which is protected by a hard reddish-brown shell, the developing fly goes through the metamorphosis from maggot to fly.

Flies have “natural enemies” that are commonly present in livestock barns. Beetles and mites devour fly eggs and larvae, adult flies are prone to diseases, and fly pupae are attacked by small parasitic wasps. Unnoticed and unaided by us, these natural biocontrol

Pest Management Recommendations for Dairy Cattle 3

agents can take a heavy toll on the fly population.

Parasitic wasps are among the most important of these natural biocontrol agents. About a dozen species occur throughout the United States. Some species perform better in different climates, and some prefer different kinds of manure and other fly breeding materials. The species best adapted to dairy farms in the Northeast is Muscidifurax raptor. This versatile species attacks fly pupae inside barns as well as outside, and it accounts for most of the naturally occurring wasps on our dairy farms.

Parasitic wasps are like “smart bombs” that live only to find and to kill fly pupae. Although the female wasp has a stinger, she cannot use it for anything except killing flies. When she finds a fly pupa, she first stings and feeds on it. This kills the fly. She then uses her stinger to lay an egg inside the pupa. The egg hatches and the parasite larva feeds on the dead fly. The young adult parasite then chews its way out of the fly’s pupal case and resumes the search for new pupae to kill. Development from egg to adult parasite is completed in about 3 weeks.

Evolution has led to a natural balance that allows both the parasite and the fly to coexist. If we think of the fly and the parasite as competitors in a race each summer, the fly has certain advantages that help it to “win” unless we intercede to level the playing field. For example, the fly develops twice as fast from egg to adult, lives longer, and lays more eggs than Muscidifurax raptor parasites. As fly populations begin to grow in late May and early June, the parasite populations lag behind. The result is that the parasite population is usually behind that of the fly by several weeks.

The parasite also lags behind the fly in developing resistance to insecticides. Many insecticide treatments for the fly therefore have the undesirable side effect of killing large numbers of parasites. If you use insecticides highly toxic to natural enemies in the early summer, you can get stuck on a “pesticide treadmill.” Each subsequent insecticide treatment kills more beneficial insects and creates conditions that require repetitive treatments to keep flies in check. This also aggravates the problem of insecticide resistance in the flies.

Parasite populations can be conserved by using insecticides that are compatible with these important biocontrol agents. Methomyl scatter baits and pyrethrin space sprays are good examples of compatible insecticides. Residual premise sprays such as permethrin, dimethoate, and rabon are highly toxic to parasites and should be used only as a last resort for dealing with occasional fly outbreaks.

PARASITE RELEASES

Along with conserving natural enemies, it is possible to go one step farther and make releases of parasites to “jump-start” their population growth in the early summer. Releases of parasites can be effective in managing fly populations if certain conditions are met:

• Waste management is a must; parasite releases complement manure management but cannot replace it.
• When insecticidal treatment is necessary for supplemental fly control, only those insecticides compatible with parasites (space sprays and baits) should be used.
• Parasites are sent from suppliers as killed fly pupae containing immature parasites. Local suppliers ship the parasites in cheesecloth bags. If most fly breeding on the farm occurs inside the barn, these bags should be stapled to posts and rafters near areas where fly breeding is a problem. If calves are housed in hutches, the bags should be opened and about 3 heaping teaspoons of pupae placed in each hutch weekly.
• Many companies who sell parasites advertise their products in farm magazines, but not all of them sell the right species or provide parasites adapted for our northeastern climate. Moreover, parasites from some commercial insectaries suffer from a debilitating disease that greatly reduces their effectiveness. Dairy farmers should look for Muscidifurax raptor and stay away from Nasonia vitripennis. Nasonia parasites are inexpensive but are inappropriate for use on our dairy farms. IPM Laboratories in Locke, NY (315-497-3129) is currently the only commercial insectary that produces and sells disease-free Muscidifurax parasites.
• Releases should be started early, preferably in middle to late May, and continued weekly until the middle of August.
• How many parasites should be released? Weekly releases of either 200 parasites per milking cow or 1,000 parasites per calf have proven effective in research trials. But every farm is different, and release rates and schedules may require adjustment to achieve a level both effective and affordable for an individual farm.
• How cost-effective are parasite releases? Prices vary, but they run at about $13.00 per batch of 10,000 parasites plus shipping charges. At a release rate of 200 per

cow (= 26 cents) per week, this means that total costs for the summer are between $2.60 and $4.70 per cow, depending on how long the releases are sustained.

In research trials, parasite release costs have been more than offset by reductions in insecticide treatments. On average, dairy farmers who use biocontrol in fly IPM programs make 80 percent fewer insecticide treatments than farmers who rely on insecticides for fly control. In addition, fly populations on IPM farms are about 50 percent lower than on conventionally managed farms.

We are still at an early stage in understanding how to use biocontrol to full advantage in fly management programs. Please share your observations, successes, and disappointments so that we can all learn together. Call us (Don Rutz at 607-255-3251 or Charlie Pitts at 814-863-7789); or contact your local Cooperative Extension agent or regional specialist.

CHEMICAL CONTROL

Insecticides can play an important role in integrated fly management programs. Chemical control options include space sprays, baits, larvicides, residual premise sprays, and whole-animal sprays. Insecticides registered for fly control are listed in Table 1, enclosed in the pouch on the back cover.

Space sprays with synergized pyrethrins or a combination of dichlorvos and synergized pyrethrins provide a quick knockdown of adult flies in an enclosed air space. Because space sprays have very little residual activity, resistance to these insecticides is still relatively low in fly populations in the Northeast. Scatter baits containing the insecticide methomyl are also very useful for managing moderate fly populations. As indicated previously, space sprays and baits are compatible with fly parasites.

A number of insecticides are labeled for use as larvicides, either for direct treatment of manure or in controlled-release formulations. Direct application of insecticides to manure and bedding should be avoided in general, because of harmful effects on beneficial insects. The only exception is occasional spot treatment of breeding sites that are heavily infested with fly larvae but that cannot be cleaned out. Controlled-release larviciding options include boluses and feed additives that result in the insecticide’s being excreted with animal feces.

Treatment of building surfaces with residual sprays such as permethrin, dimethoate, naled, and rabon has been one of the most popular fly control strategies over the years. High levels of resistance to these insecticides are now very common. These materials should be used sparingly and only as a last resort to control fly outbreaks that cannot be managed with other techniques.

Whole-animal sprays can be made directly on the animals to manage stable fly problems. Although this approach can provide needed relief from biting fly pressure, the control is rather short-lived.

FLY CONTROL IN MILK ROOMS

Milk rooms represent a special case. Because sanitary codes restrict insecticide use in milk rooms, the only chemical treatments recommended are space sprays with synergized pyrethrins (read label carefully regarding protection of milk and milk handling equipment) and placement of Vapona strips. Use of sticky ribbons and cultural practices that restrict fly entry into the milk room can greatly reduce the need for insecticidal treatment in the milk room.

Warning. Always read product labels carefully before applying any insecticide; mix and apply as directed, do not overdose, do not treat too often, and follow all precautions exactly. Remember that improper practices can lead to illegal residues even when correct materials are used. It is illegal to use an insecticide in any manner inconsistent with the label.

BIOLOGY AND IMPORTANCE

Several fly pests attack cattle on pasture. These pests include horn flies, face flies, horse flies and deer flies, black flies, mosquitoes, and biting midges. Each has distinctive habits, life histories, and economic importance.

BIOLOGY AND IMPORTANCE

In contrast to the fly pests, lice are relatively small and inconspicuous. Four species of lice attack dairy cattle in the Northeast. By far the most common is the cattle chewing louse, Bovicola bovis. This species is about 1/8 inch long when fully grown, has a yellow-brown appearance, and is most commonly found on the animal’s neck, back, hips, and tailhead. B. bovis are not blood feeders, but they use their mouthparts to rasp away at animal skin and hair.

In addition to chewing lice, three species of sucking lice feed on the blood of dairy cattle: the long-nosed cattle louse (Linognathus vituli), the short-nosed cattle louse (Haematopinus eurysternus), and the little blue louse (Solenopotes capillatus). Sucking lice have mouthparts specialized for penetrating animal skin. They spend most of their time with their heads firmly attached to the skin. Sucking lice often take on a darker appearance than chewing lice as they become engorged with blood.

Female lice lay their eggs by attaching them to hairs with a strong glue to prevent them from falling off. The eggs, known as nits, hatch in 10 to 14 days, and the young lice (nymphs) complete their development within several weeks. Lice, in contrast to some other livestock pests, are permanent parasites that spend their entire lives on the host animal.

All four types of lice cause extreme annoyance to the host animals. Milk production declines in heavily infested cattle, and the animals’ preoccupation with rubbing leads to hair loss, reduced feed conversion efficiency, and general unthriftiness. Infested animals become irritable and difficult to work with, especially during milking. People working around lousy animals are exposed to greater risk of injury and are also annoyed by stray lice they pick up from infested animals during handling.

Although louse problems are generally perceived as being most severe during the fall and winter months, animals of different age groups show distinct differences in the seasonality of infestation. Lice are most common on mature cows in December through March, with peak populations found in March. In contrast, calves housed inside barns show high levels of infestation throughout the year, with peak populations in June. This difference may be due to the fact that cows are placed on pastures in the spring, where exposure to direct sunlight heats the skin to levels lethal for most lice. Calves kept in the cool environment of the barn are not able to take advantage of sunlight’s natural curative properties.

Other animal housing conditions also affect louse populations. Cows in stanchion barns are twice as likely to be infested as cows in free stalls, owing to the greater opportunities of unrestrained animals to groom themselves. Calves housed in communal pens inside barns are 10 times as likely to be infested as calves in individual hutches. The effectiveness of hutches results from a combination of the animals’ isolation from one another and the opportunity for calves in hutches to spend time in direct sunshine.

MONITORING

Because lice often are inconspicuous, many producers do not detect them until their cattle begin to show hair loss from the animals’ grooming activities. But by the time the infestation has progressed to this stage, populations of lice are already well above economic injury levels, and treatment becomes very difficult owing to the large numbers of lice involved. Effective management of cattle lice below economic injury levels requires sampling of apparently healthy as well as noticeably lousy animals for the presence and relative numbers of lice. Such surveillance should be conducted every 2 to 3 weeks throughout the fall, winter, and spring months.

Lice can be monitored easily with a flashlight and a little practice. Sampling involves carefully inspecting sections of skin on a representative sample of animals in the herd, either 10 percent or 15 animals in each group: mature cows, heifers, and calves. The best regions to inspect are the head, neck, shoulders, back, hips, and tail. If sampling indicates that B. bovis is the dominant species present, assessment of the neck and tailhead alone is sufficient to detect most infestations. Treatment is recommended when counts average over 10 lice per square inch.

MANAGEMENT

CULTURAL CONTROL

Producers can save on the cost of insecticide treatments for lice by adopting cultural control practices. First, replacement animals brought into the herd should be isolated and carefully inspected for lice before they are allowed to mingle with the rest of the herd. Second, careful and regular monitoring for lice can detect problems before an infestation gets out of control. Third, housing calves in hutches will reduce infestations on these valuable replacement animals by 90 percent without any insecticide applications.

SARCOPTIC MANGE

Sarcoptic mange is a condition caused by another, smaller species of mite, Sarcoptes scabiei. The skin lesions arising from infestation by these mites are so severe that sarcoptic mange is handled as a quarantinable disease.

Unlike lice and Chorioptes mites, the microscopic sarcoptic mange mites burrow deeply into the skin, laying eggs inside the burrows. The eggs hatch into the larval stage. The larval mites then leave the burrows, move up to the skin surface, and begin forming new burrows in healthy skin tissue. Development from egg to adult is completed in about 2 weeks. The lesions resulting from infestations by these mites are a consequence of the reaction of the animals’ immune system to the mites’ presence. Because of the intensity of the animals’ immunological response, it takes only a small number of mites to produce widespread lesions and generalized dermatitis. Animals show remarkable variation in the extent to which they react to the infestation, however. It is not uncommon to have healthy-looking animals in stanchions next to animals with lesions over much of their bodies.

MONITORING

Mange lesions often first appear around the tail, anus, thighs, udder, legs, and feet. The first sign of infestation usually is hair loss from the animals’ rubbing as they try to relieve the itching. As the infestation progresses, the lesions become larger and bloody or moist, followed by the formation of thick, crusty scabs. If left untreated, the lesions may eventually cover the animal’s body. When this happens, the entire hide may take on a thick, wrinkled appearance.

Sarcoptic mange mites are nearly invisible to the naked eye. In addition, mange is only one of several conditions resulting in somewhat similar symptoms. The only way to diagnose mange accurately is by having skin scrapings taken by a veterinarian or other trained professional. Scrapings are made with a scalpel by abrading rather deeply into the skin. The scrapings are then brought back to the laboratory and examined under a microscope for the presence of mites and for species determination.

MANAGEMENT

PREVENTION

Mange mites, like lice, are permanent external parasites that do not survive away from the host for very long. The best way to minimize the risk of introducing the mites into a herd is to be cautious when buying or boarding new animals. Avoid any animals that show visible skin lesions or that appear to be abnormally itchy or agitated. As an extra precaution, it is wise to segregate all newly purchased animals from the rest of the herd for several weeks and keep them under observation. A veterinarian should be called in if any of the animals show signs of unusual itchiness.

CHEMICAL CONTROL

Several pesticides used for controlling cattle lice also are effective against chorioptic mange mites. These are shown in Table 4. Because of the severity of sarcoptic mange, it is regarded from a regulatory standpoint as a reportable disease. Therefore, the threshold for placing a herd under quarantine is the discovery of a single mite on one animal.

Once a herd has been placed under quarantine, animals may not be moved off the farm except for slaughter. Every animal in the herd must then be treated with high-pressure hydraulic spray equipment by certified pesticide applicators under the supervision of a state veterinarian. Either two or three treatments must be made, depending on the choice of insecticide used, with treatments spaced 7 to 10 days apart. Quarantine is lifted when post-treatment skin scrapings demonstrate the infestation has been eradicated. Because high-pressure spray equipment is necessary to ensure penetration by the spray into the skin, “home remedies” applied with low to moderate pressure gear of the type owned by many dairy producers are never successful.

PESTICIDE EMERGENCY NUMBERS

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NEW YORK POISON CONTROL CENTERS

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Western New York 1-800-888-7655

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Rochester 1-800-333-0542

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Central and Southern Tier New York 1-800-252-5655

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Eastern and Northern New York 1-800-366-6997

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New York City 1-212-340-4494

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Long Island 1-516-542-2323

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■ Air

Hang garments outdoors to air.

■ Prerinse

Use one of three methods:

1. Hose off garments outdoors.
2. Rinse in separate tub or pail.
3. Agitate in automatic washer.

■ Pretreat (heavily soiled garments)

Use heavy-duty liquid.

■ Washer Load

Wash garments separately from family wash. Wash garments contaminated with the same pesticide together.

■ Load Size

Wash only a few garments at once.

■ Water Level

Use full water level.

■ Water Temperature

Use hot water, 140^oF or higher.

■ Wash Cycle

Use normal 12-minute wash cycle.

■ Laundry Detergent

Use a heavy-duty detergent. Use amount recommended on package, or more for heavy soil/hard water.

■ Rinse

Use two full warm water rinses.

■ Dry

Line dry to avoid contaminating dryer.

A Cornell and Penn State Cooperative Extension publication

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by Cornell Cooperative Extension or Penn State Cooperative Extension is implied.

This publication is issued to further Cooperative Extension work mandated by acts of congress of May 8 and June 30, 1914. It was produced with the cooperation of the U.S. Department of Agriculture, Cornell Cooperative Extension, and Penn State Cooperative Extension.

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