Every season has its trials when it comes to horse-keeping. Although we might pine for sunny skies when we’re battling spring mud, the turning of the seasons quickly reminds us of one of winter’s little blessings — no buzzing, biting, annoying flies! When those squadrons of pests descend on us from above, driving us and our horses to distraction (not to mention spreading filth and disease), it’s pretty easy to start wishing for winter again.

Fortunately, we’re not defenseless. Ever since flypaper was invented (in 1861, for you trivia buffs), humans tirelessly have applied themselves to the Battle of the Bugs — and while we might never win the war, we’ve certainly triumphed in some of the skirmishes. These days, we have quite an arsenal at our disposal to attack and repel flies. From electric bug zappers, to pheromone traps, to parasitic wasps that feed on fly pupae, we’ve explored all sorts of ways and means of getting rid of flying insects.

The cornerstone of any fly counter-aggression program in any barn or stable is a bottle of fly spray. When we’re planning to go on a trail ride through the woods, we squirt the stuff on our horse’s coats (and spray the human version on our clothing and exposed skin). When we turn our horses out in the field on a buggy afternoon, we circle their eyes with roll-on fly repellents and tie slow-release insecticide tags on their halters. Although nothing’s perfect in keeping the bugs off our equines, fly repellent formulas do help. But with their chemical smells and labeling lists of barely pronounceable ingredients, it’s not unreasonable to wonder just how toxic these products really are. Are they truly safe for your horse? For you? For the environment?