Pest Control for Horses

Horse operations attract a lot of visitors, many of them welcome. People come to admire the horses and the beautiful barns and paddocks where they are kept. Then there are the biting insects and the wild things, winged or legged, that come uninvited, and all too often bring along disease.

Stable hygiene is the first line of defense in keeping unwanted visitors out of a barn. Another place to exercise good stable hygiene is in the feed room. The storage of feed can either deter or attract rodents and other critters that don't belong in the barn.

"Good sanitation goes a long ways," said Dr. Tom Barnes, a University of Kentucky extension agent specializing in wildlife control in barns and pastures. Barnes' expertise is in controlling field critters such as raccoons and opossums, as well as rodents, bats, and birds. 

For feed storage, Barnes recommends using receptacles with firmly attaching lids. Commercially manufactured feed bins are made exclusively for this purpose. Another solution is to buy an ordinary large, heavy duty plastic trash can that has a lid that snaps into place. Under no circumstances is it recommended to leave sacks of feed out on the floor. Exposed feed lures rodents and prowling wildlife that venture into the barn.

Biting insects have long been a bane to horses and people who work around horses. In the few short years since West Nile virus (WNV) took center stage as a public health threat, we've become more aware than ever of the need to eliminate mosquito breeding grounds.

Mosquitoes --and birds, which carry the disease as they migrate--have gained notoriety as WNV vectors, but mosquitoes have always been health threats to humans and horses. For horses, mosquitoes are carriers of the common strains of sleeping sickness known as Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE), as well as WNV.

Vaccines to protect horses against EEE, WEE, VEE, and WNV do give farm managers a measure of defense against those mosquito-borne diseases. However, any smart farm manager will be the first to point out that good stable management--i.e., preventive management--is crucial, to give the vaccination program its best chance for success in protecting horses against disease.

As the warm spring and summer months approach, one might want to consider some of the more aggressive pest and insect control measures for inside and outside of the barn. Insect control systems take different approaches. Makers of the different systems note that horse facilities might need to employ more than one type of system to control all species of insects inside and outside of the barn.

Regarding insects, owners should note that beginning in 2001, when Kentucky and the mid-Atlantic states saw a dramatic outbreak of early- and late-term abortions, the Eastern tent caterpillar (ETC) moved into first place as the number one creepy-crawly nemesis to breeding operations. The ETC is not a biting insect, but it has been implicated in connection to mare reproductive loss syndrome (MRLS), and is regarded as a major nuisance by horse farm managers in regions of the country it inhabits.

Fly Away
Fly season starts as soon as it gets warm enough in the spring to start your garden, after the danger of frost is past. If uncertain when that is in your area, consult your county extension agent. Generally, fly season runs through September or October in southern regions, or it can wind up by the end of August in some northern regions. osquitoes also like warm weather, and are more active breeders during wet, rainy seasons.

Biting flies can drive horses crazy, interfering with training and grooming activities. Flies also can spread infectious diseases. Several fly species lay their eggs in manure piles. One species, the bot fly, lays eggs on the horse, which then ingests the eggs. The bott fly is an internal parasite.

Misting Systems
Automatic misting systems, also called overhead systems, can be built into a barn at the time of construction or they can be added on to an existing facility. The automatic systems dispense a light mist of insecticide down into the barn via nozzles that are installed overhead in the stalls, aisles, or wash racks. The systems are timer-operated and fully adjustable, allowing farm managers to set the duration of misting intervals and the number of times per day the barn is misted.

Insecticide drums are available a variety of sizes. The drum is filled with insecticide that is dispensed by a pump through tubes into nozzles. For a larger barn, a 55-gallon system is extremely low maintenance. It requires being filled once at the beginning of the season, figuring that an insect season runs about five months, and average use is going to be anywhere from six to 10 gallons of insecticide a month.

It is important to use one of the recommended insecticides in overhead misting systems. These include the natural and synthetic pyrethrin family of chemicals. Order refills of the insecticide from the company that sold the system, or if buying insecticide through another supplier, check the label to be sure the insecticide can be used in an overhead system. Citronella, for example, is not for use in an overhead system.

Costs of the systems vary based on two variables; size of drum and number of nozzles. A basic unit that includes the drum, pump, and timer can start at about $550 and range to about $665. Nozzles and tubing cost approximately $20 per nozzle.

Foggy Notes
H.D. Hudson Manufacturing in Chicago, Ill., manufactures mosquito and insect control sprayers and foggers. These types of equipment are generally used by professional exterminators and they are also used by consumers for home and private use. They have not traditionally been used by the horse industry, but they do offer an alternative to the overhead systems. Sprayers are hand held, and there are two types of foggers. One can be set in place, but can be easily relocated for use in different places. The stationary fogger is very adaptable for use in barns. It has a range of up to 100 feet and can be set to apply anywhere from one to five gallons of insecticide per hour. The sprayer and the stationary fogger run on electricity and range in price from $150 to $200. The motor runs softly, making a low hum similar to a vacuum cleaner. The ULV Porta-Pak fogger, which is worn on the back, is designed for fogging a range 150 feet wide as a person covers the ground on foot. This unit has a gas engine and costs approximately $1,200.

Hudson does not make the insecticide that would be used in the equipment. When selecting an insecticide for use with this type of equipment, be sure to read the label and follow instructions regarding health and safety concerns for both humans and horses.

Hudson also makes the pump-up, compression bottles, and the trigger "spritzer" bottles (the kind used for household cleaners) that can be used to apply fly spray directly onto the horse. Products that combine fly repellent and sunscreen can be purchased at the neighborhood tack shop.

Beneficial Brigade
Mother Nature had it all figured out. Some species of insects would feast on the larvae of flies, thus keeping down the population of those disease-carrying insects. Flies wreak their havoc within a remarkably short lifespan, 24 hours long, during which one adult female fly can lay 2,000 eggs. Creating a "beneficial insect" that feeds on the young of flies was nature's way of fighting insects with insects. These beneficial insects' purpose in life is to kill filth flies by interrupting the life cycle of the prolific pest.

Spalding Laboratories in Arroyo Grande, Calif., is a biological company that produces beneficial insects. Another biological company, Kunafin, in Quemado, Texas, produces The Insectary system. The beneficial insects are packed in an air permeable bag. Customers take the bag to a manure pile, release the insects, and let the beneficial insects eat the fly maggots as they emerge from eggs around the manure piles. Beneficial insects do not carry disease and do not bite humans, horses, or dogs. They are tiny, and hover about one foot off the ground above the manure piles.

If a horse operation ever managed to wipe out all of the flies present on a given day, repopulating it would be a simple matter of one female fly arriving on the property and laying her eggs. Most operations remove all muck from the barn each day, and wherever the muck is taken, the manure heap on the property then becomes a destination for flies to lay eggs. Then, too, the overhead spray systems that work inside the barn on adult flies do not eliminate the source of the problem.

Beneficial insects will die out if there are no maggots for them to eat. A horse operation might need to replace these beneficial insects at different intervals. A bag of 15,000 insects, adequate for up to 15 horses, should cost about $15, and a bag of 30,000 insects, effective for 16 to 40 horses, should cost about $25.

Fly Trap
Newman Enterprises in Omro, Wisc., makes the Horse Pal fly trap for use outdoors against horseflies and deerflies. The trap itself is the lure to these insects--no bait is used, but as long as the trap is set up so that the horseflies and deerflies see it, these insects will fly into it, and become trapped in a containment receptacle on top. The receptacle would be emptied of dead flies, and then it is ready to trap more flies. Equine infectious anemia, vesicular stomatitis, anthrax, and Lyme disease are a few of the diseases attributed to horseflies and deerflies that carry health risks to humans or horses.

Collars & Leg Bands
R&R Enterprises in Granite Bay, Calif., makes a line of Defy the Fly products for horses, cows, and dogs. The fly and mosquito repellent collar and leg bands for horses were released onto the market in 1998. These can be used either when horses are turned out or stabled. The collar and leg bands are impregnated with repellents to provide relief to the head, neck, and legs for up to two months. Three all-natural repellents are used--geraniol, citronella, and cedar oil. All are Environmental Protection Agency-approved as ingredients that are safe if ingested. Price for the Horse Fly Collar is $15.95. A set of four Horse Fly Leg Bands costs $24.95.

Fire Ants
Dr. Phil Nichols, staff entomologist for Middleton Lawn and Pest Control in Orlando, Fla., talked about the mosquito management and fire ant control services offered by Middleton.

Fire ants are a problem in the southern part of the U.S., especially in Florida, but also in Texas, and just recently they are starting to be noticed in Southern California. These biting insects build large mounds in pastures where horses are turned out. They can be harmful to foals, and with the bigger mounds, Nichols said, "The ground underneath is very soft. There's a possibility of a horse stepping into one of those mounds and possibly breaking a leg."

Fire ants have been a problem in the U.S. since 1946. In recent years, Nichols said, "With the drier weather in Florida, there seem to be bigger mounds."

Middleton offers a two-step approach to fire ant control. One, larvicide is injected directly into the bigger mounds. Two, granular bait impregnated with insecticide is set out near the smaller mounds.

The company does not spray for mosquitoes, but offers consulting services for horse farms, such as getting rid of any receptacles that can hold standing water, which serve as a breeding ground for mosquitoes.

Horse farm managers might decide that combining two or more methods of insect control works best to address indoor and outdoor areas at their facility.

Varmint Repellent
We return to UK's Dr. Tom Barnes for more on the bats, birds, and other varmints that can infiltrate our barns and pastures.

Exclusion methods of wildlife control are the best solution for birds and bats, Barnes said. Exclusion methods are barrier devices that would be put around an area where the pests like to congregate.

"In many situations, it's tough to deal with bird problems," Barnes said. Plastic bird netting set over an area where birds like to roost will discourage them from roosting. Porcupine wire, the generic term for products that "a bunch of different companies make," he said, has short, sharp spikes in different areas. Staple the porcupine wire in a strip and it discourages birds. Sticky repellent, used like caulk, is another exclusion method.

"Poisons can be used as a last resort, but typically, I don't recommend those," Barnes said. "If somebody has a serious problem, I'm going to recommend them to the USDA Wildlife Services." Before using poison, consult your state's agency office.

Because of WNV concerns, "If you see dead birds on your property for no reason, take them in to adiagnostic lab." When handling a dead bird, wear rubber gloves, and put the carcass in a plastic garbage bag that can be sealed. If you suspect bats in your barn might have rabies, take a carcass to a diagnostic lab.

Equine protozoal myeloencephalitis (EPM) is an infectious disease of the spinal cord associated with a protozoan parasite, Sarcocystis neurona. Opossums have been identified as hosts for the parasite that causes EPM.

With rodents, and the pedestrian wildlife that can be lured into barns by exposed feed, Barnes said, "There, you have to think of exclusion as being the best solution. You'd have to go with metal, hardware cloth, a welded wire that they can't chew through. They can get through a pretty small hole, so you have to make sure that all around your barn is well sealed up."

About the Author

Bettina Cohen

Bettina Cohen is a past contributing writer to The Blood-Horse magazine.

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