Biting and stinging insects tend to come out in force in the summer, and if your barn is overrun by bugs, you likely need some help. Our Church’s Mobile Veterinary Service team knows that battling pesky insects can be extremely frustrating, so we explain what pests are problematic for horses and provide tips to help with prevention and control.
Filth flies are problematic for horses
Knowing your enemy is important in any battle, and identifying the problematic insect can help you devise appropriate management strategies. Filth flies develop in moist organic debris, such as aging feces, soiled animal bedding, near leaky waterers, and rotting feed debris, and reproduce from about May to early October. An adult female lays 50 to 150 eggs every few days, small maggots hatch from the eggs, feed on the bacteria growing in the debris, and eventually mature into winged adults that live about one to three weeks. Filth flies include:
- House flies — Musca domestica are typically the most prevalent flying pest found around horses and livestock. They feed on facial secretions and sweat, and are often found in high numbers on an animal. House flies have sucking mouthparts, and to eat solid foods, they vomit on the food, and then suck up the material that their saliva and digestive fluids have liquefied.
- Face flies — Musca autumnalis are closely related to house flies and can be hard to distinguish. They are non-biting flies that feed on facial secretions, and can usually be found around a horse’s eyes, nose, and muzzle, and can be immensely annoying.
- Stable flies — Stomoxys calcitrans are blood-sucking flies that commonly feed on an animal’s legs. Stable flies have piercing, sucking mouthparts, with a painful bite. They are responsible for transmitting diseases such as equine infectious anemia (EIA) and anaplasmosis.
- Horn flies — Haematobia irritans are primarily found on pastured cattle, but can also bother horses, sheep, and goats. They like to congregate on an animal’s back, shoulders, and sides where they use their piercing mouthparts to take about 40 blood meals a day.
House, face, and stable flies also can invade wounds or moist areas on the horse’s body and cause summer sores that manifest as intensely itchy, nonhealing skin lesions. Lesions are most commonly seen around the horse’s hooves, but also on the prepuce, lower abdomen, and eye and lip margins.
Managing filth flies around horses
Methods to help prevent and control filth flies include:
- Reducing breeding sites — Reduce sites where these insects can breed by:
- Keeping feed dry and avoiding ground feeding
- Removing manure from pastures and living spaces at least twice a week
- Spreading or composting waste
- Replacing bedding weekly, and considering wood shavings or sawdust, which produce fewer flies than straw
- Placing waterers in well-drained areas away from feeding locations
- Insecticides — Always read and follow label instructions carefully when using chemical insecticides to prevent toxicity. Insecticides are more effective when you reduce debris in the areas where insects lay eggs.
- Stingless parasitic wasps — These small, ant-like insects that kill filth fly pupae occur naturally around animal premises. You can purchase more parasitic wasps to supplement natural populations.
- Fly repellents — Fly repellents can provide temporary relief from stable flies.
Aquatic biting flies are problematic for horses
Aquatic biting flies include:
- Horse and deer flies — Horse and deer flies belong to the Tabanidae family. The females have knife-like mouthparts and feed on animals during the day, inflicting a painful bite and leaving a bloody feeding site. They lay eggs on vegetation around water, and the adults can travel several miles to find a host.
- Black flies — Black flies are gnat-like insects that are most active from May until July, and most commonly attack pastured horses during the day. Larvae develop in flowing creeks, streams, and rivers, and adults can travel several miles from their origination to find a host. They cause scabby lesions, typically inside the ears and on the neck, chest, and belly.
- Mosquitoes — Mosquito larvae develop in still water containing decaying leaves and algae, such as rain-filled depressions, naturally occurring tree holes, swamps, and artificial containers, including water troughs. They can transmit West Nile virus (WNV), Western equine encephalitis (WEE), and Eastern equine encephalitis (EEE).
- Biting midges — Biting midges, which are also called sand flies and no-see-ums, belong to the Ceratapagonidae family. They lay their eggs in moist areas around ponds, marshes, and stock tanks, and the larvae develop in muddy conditions. Biting midges feed most actively at dawn and dusk, and thousands can feed on one horse. They can cause sweet itch, a hypersensitivity to the fly’s saliva that creates a chronic, seasonal skin irritation.
Managing biting aquatic flies around horses
Methods to help prevent and control biting aquatic flies include:
- Providing shelter — Keeping horses inside or in deep shade during daylight hours can protect them from horse, deer, and black flies. Keeping them behind screened doorways and windows can protect them from mosquitoes and biting midges.
- Managing water sources — Reduce water sources around your farm by:
- Cleaning water tanks and garden containers
- Disposing of old tires and other potential water containers
- Drilling holes in tire swings
- Traps — Insect traps have not been proven to significantly reduce insect populations.
In addition, ensure your horse is vaccinated against WNV, EEE, and WEE, and tested for EIA once a year. You can also provide a fly mask, fly sheet, and fly boots to help inhibit flies from biting your horse.
If you would like more suggestions to help manage your insect problem, contact our Church’s Mobile Veterinary Service team. We can find a strategy to address the pesky bugs and help your horse suffer fewer pest problems.
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