If insects are making life miserable for you and your horse, you're probably searching frantically for a fly spray that lives up to its claims. The trick? Learn how to read—and UNDERSTAND—the label on that stuff with these six important secrets:

1.Go for the small print: The product claims in the big print are the manufacturers' salespeak, or what they think will convince customers to buy that product. Yes, this language is highly regulated by the EPA, but it's the small print—the list of active ingredients and their percentages—that tells you the most, because the types and levels of active ingredients vary from one spray to the next, determining how well each will work.

2.Know your active ingredients: Active ingredients include insecticides, repellents and synergists. Insecticides are what killthe insects. Repellents simply repel them. Some insecticides both repel and kill. Many fly spray formulas also include synergists, which are additives that increase the effectiveness of the insecticides and repellents.

3.Understand pyrethrins, pyrethroids and the role of synergists: The most common insecticides in equine fly sprays are pyrethrins and pyrethroids. Pyrethrins are extracted from certain types of chrysanthemums. They provide very quick knockdown, killing the insects quickly. However, pyrethrins are broken down rapidly by sunlight, so synergists—usually Piperonyl butoxide and/or Butoxypolypropylene glycol—are often added to protect and extend the effectiveness of the formula.

Pyrethroids are synthetic forms of pyrethrins. The most common pyrethroids are permethrin, cypermethrin and resmethrin. Pyrethroids are not as easily broken down by sunlight, so they can remain effective for several days. Both pyrethrins and pyrethroids have a long track record for effectiveness and animal safety on horses and dogs. You might also come across an ingredient called coumaphos, although it’s more common in livestock or cross-species fly control products.

4. Think percentages: If you’re examining two bottles of fly spray trying to figure out which one is more effective, the amount of "actives" in each formula is key. Say Brand A contains .05% pyrethrins and Brand B contains .90% pyrethrins. That means there’s 18 times more active ingredient in Brand B. Which do you think will be more effective? It’s easy to be misled by brands with big claims but very low levels of actives, and therefore a lower price. With fly sprays, as with most things in life, you really do get what you pay for.

5. Consider oil vs. water: Another difference between fly sprays is that some are water-based, while others are oil-based. There are advantages and disadvantages to both. Oil-based sprays tend to work the fastest, in part because the insects just plain drown or suffocate in the oil. Oil-based sprays also put a nice shine on the horse’s coat when first applied. That said, oil attracts dust, which then sticks to the coat—so much for the shine! Plus, some horses' skin gets burned if they’re sprayed with an oil-based product and then turned out in the sun.

By contrast, water-based sprays are less irritating to the horse’s skin, and because there’s no oil to attract dust and dirt, the horse tends to stay cleaner longer. Some water-based fly sprays include ingredients to help them stay on the coat even if it’s rainy or the horse gets sweaty.

6. Natural isn't always best: Last but not least are the "natural" fly sprays. These typically contain a combination of natural oils known to repel various insects. The bottom line: Because these oils only repel insects rather than killing them, natural fly sprays are never going to be quite as effective as fly sprays with insecticides. This can confuse uneducated consumers who expect the natural sprays to yield the same results as the insecticide sprays. But if you prefer the natural option, it's a good bet when the bug population is low, such as in the early spring, late summer and the fall.

So now you know!

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