Published June, 2011

Following heavy rains throughout April and May in Kentucky, June's high temperatures mark summer's early arrival. And with the heat, haze, and humidity come bugs, including several types of flies, ticks, and stinging pests. Because many insects and their relatives are potential disease carriers, horse owners should know which ones are simply nuisances and which could be potentially dangerous to equine health.

"The general warming trend we are experiencing has a big impact on our insect populations," said Lee Townsend, PhD, University of Kentucky College of Agriculture entomologist. "Add moisture to the heat and you have the potential for greater problems, so it's important to review some of the key pests to anticipate."

The Ubiquitous Fly

Flies are common pests whose persistent biting can make horses nervous, difficult to manage, and sometimes dangerous to work around when the horse stomps his feet, kicks, and swishes his tail to deter insects. Biting flies also can interfere with grazing, and animals can even injure themselves if they run to escape being bitten. Vigorous stamping is another fly-related issue, because the repetitive force can cause hoof cracks and contribute to loose and lost shoes.

Most biting flies are attracted to movement, dark surfaces, carbon dioxide, and warmth--which is how they find horses.

"Horse flies are sun-lovers and rarely enter barns or shady areas, so grazing animals at night and stabling or providing shelter during the day can provide effective relief," Townsend said.

House flies are potential carriers of human and animal pathogens and can also be a nuisance to neighbors. House fly maggots are found in moist material, such as manure, garbage, or rotting hay, where development takes seven to 14 days.

Stable flies resemble house flies but have a prominent beak that delivers a distinctly painful bite. Stable flies usually attack the flank or below the knee, causing horses to stamp their hooves and/or kick at their belly. Stable fly maggots develop in decaying organic material, such as a mixture of straw, spilled feed, hay, and water/urine, with a reproductive cycle that takes 21-25 days.

Fly control is not easy. "There's no magic solution for fly problems, but recognizing problems early and correcting them if possible will go a long way toward keeping fly numbers manageable," Townsend said.

Eliminating breeding sites is key to successful stable fly and house fly control. Clean and remove manure from barns and paddocks once a week to break flies' life/reproductive cycles. Spread removed manure and muck in a thin layer where appropriate, or compost it. Promote good drainage, and prevent wet areas from forming around waterers. Insecticides can help reduce house and stable fly populations, but this is a temporary remedy. A good fly management program will ensure that wet and warm organic materials are removed promptly and encourage thorough drying to prevent the proliferation of breeding sites.

Townsend's suggestions for dealing with flies are as follows:

• Use screens in feed and tack rooms and stalls;
• At entryways, install fans that blow down and out to keep flies from entering barns;
• Use insecticides if a fly problem has developed (this is only a temporary fix, as it does not address the root issue--namely that flies have access to moist breeding material). Follow the manufacturer's instructions carefully for proper insecticide use;
• Use fly traps and sticky paper to capture flies;
• Consider using a commercial firm that specializes in fly predator release programs; and
• Bring horses into barns during the day to provide them with fly relief.

Ticks

Ticks are blood-sucking relatives of insects that attach to a host (human, horse, dog, etc.) for sustenance. Some can transmit diseases such as ehrlichiosis, Lyme disease, and piroplasmosis, and cause skin irritations and even anemia (low red blood cell count).

Ticks can be found in woody areas that have heavy growth and brush, which harbor mice (another important tick host). Removing brush to let sunlight in and keeping pastures well-trimmed can make paddocks inhospitable to ticks.

The lone star tick and American dog tick are the most commonly found tick species in Kentucky, and both will attack horses, Townsend said. If you spot a tick on a horse, remove it promptly using tweezers and a straight pulling motion to ensure removal of the entire tick. Do not twist or squeeze, and do not use petroleum jelly, matches, or other similar removal methods.

Repellents and insecticides containing permethrin or cypermethrin are very irritating to ticks and will provide several hours of tick protection for horses. Check the lower body, especially the legs, and mane regularly to prevent infestation.

Wasps and Bees

Paper wasps often build open nests under barn eaves and other protected places, according to Townsend. Late spring is the best time to watch for these nests and destroy them as they are being established. This reduces the chances for accidental encounters and possible stings in late summer or early fall.

Honey bees occasionally become a problem around water troughs, especially during very dry summers.

"Bees need water to air condition their colonies and will recruit other bees to a reliable source," said Townsend. "In some cases they seem to be aggressive toward horses that are nearby."

For more information, see University of Kentucky publications Horse Flies and Deer Flies, Insect Control for Horses, Horse Farms, and Stables, Fly Control Around Horse Barns and Stables, Managing Ticks on Horses, and the April 2011 issue of Equine Disease Quarterly.

Karin Pekarchik is an editorial officer in Agricultural Communications Services.