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Horseflies and their cousins (deerflies) feed on your horse's blood, but unlike the blackfly they do not target any specific areas. They have a powerful and painful bite and can ambush your horse anywhere on his body, resulting in extreme discomfort and even the development of nodules.
The use of repellents is the only really effective direct defense against these nasty flies since they don't discriminate in which body areas they target. While repellents do provide some protection, they shouldn't be viewed as a bulletproof shield since horseflies will often ignore repellents. Test various brands and see which you have the best results with.
While there aren't perfect shields for horseflies, you can minimize their appearance by knowing what landscapes they favor. Horseflies prefer wooded areas, which is why they can be a particularly nasty nuisance during trail rides – when we ride through wooded trails we're entering their territory! If your horse's pasture is grassy and clear he probably will not be exposed to a significant level of horseflies.
If it's not possible to pasture your horse in open, exposed locations then consider stabling him during their prime feeding times: early evening.
Mosquitoes are equal opportunity offenders, all too happy to target us as quickly as they will target our horses! Repellents can provide a nice defense against these pests, but as is the nature of repellents they aren't 100% effective.
The best way to minimize mosquito assaults is to try and control their population. Mosquitoes favor hot, humid and swampy locations, so unfortunately putting a stop to them entirely may be impossible for some of us depending on the climate and landscape where we live. That having been said, one common mistake that many horse owners commit is leaving standing water sources nearby.
Mosquitoes take to stale standing water like a fly to dung. If your pasture or property contains a small pond or pool of water, try to keep your horse as far away from that water as possible! If your fields get partially flooded with water during spring or after serious rainfall, try to find ways to drain the water out of the area. Finally, never allow water troughs to become old and stagnant – make sure your horse receives fresh water daily.
The good news is houseflies are the only type of insect within this article that doesn't actually bite your horse. The bad news is they are still nuisances that can distract and annoy your horse, as well as pass on diseases.
Houseflies target your horse's eyes since they feed upon the liquid secretions of the eye. As such the best defenses are:
Repellents can be somewhat effective, but I discourage their use for housefly defense since you can accidentally expose your horse's eyes to the repellent if you're not careful. If you do choose to use repellent, never directly spray repellent around your horse's face or eyes. Instead spray some on your hand or on a cloth and carefully wipe the repellent around your horse's face and eyes. Don't apply the repellent so close to the eyes that they might cause irritation.
These are the tiny flies that incessantly swarm around your horse's neck, mane and tail, causing no end of irritation to your equine partner. Their bites, while not nearly as painful as that of a horsefly, can still cause discomfort and a great deal of itching. Often horses will furiously rub their manes or tails in response to this itching, thereby causing hair loss and even raw, bleeding skin.
Sandflies primarily feed around dusk, so the best defense against these pests is stabling your horse during their prime feeding time. Providing your horse a box fan in his stable can also help assist him in keeping these tiny pests away, not to mention help him cool down during those hot summer months.
Controlling all of the above flies is not simply a matter of our horse's comfort, though as responsible owners we should certainly do anything we can to alleviate our horse's discomfort anyways. Controlling the exposure of our horse to these flies is also a matter of health and longevity since the insects are notorious hosts of diseases.
Although it's not possible to remove flies from the equation entirely during the summer months, as you can see there are ways to help our horse and combat each of the main offenders.