Do you understand what the label means on your horse fly spray? If insects are making life miserable for you and the equids on your property, you’re probably looking for a fly spray that lives up to its claims. What’s the solution?

Learn how to read—and understand—a fly spray label with the six important secrets from this article. 

1. Read 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. This language is highly regulated by the EPA. However, it’s the small print—the list of active ingredients and their percentages—that tells you the most.

The small print gives the types and levels of active ingredients, which vary from one fly product to the next. Those are the details that determine how well each product will work. 

2. Know Your Active Ingredients

Active ingredients include insecticides, repellents, and synergists. Insecticides kill insects.

Repellents simply repel insects (the types of which will be listed on the label).

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 kill 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 long track records 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 and 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 turned out in the sun.

Water-based sprays are less irritating to the horse’s skin. Also, because there’s no oil to attract dust and dirt, the horse tends to stay cleaner. 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 Better

The “natural” fly sprays typically contain a combination of natural oils known to repel various insects. Because these oils only repel insects rather than kill them, natural fly sprays are never going to be quite as effective as fly sprays with insecticides.

If you prefer the natural option, try using them when the bug population is low, such as in the early spring and late fall. 

This article is based on a story from Practical Horseman Magazine.

Further Reading

Equine Insect Repellents for Horses. Dr. Nancy Loving. MySeniorHorse.com