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6 Tips for Finding the Best Fly Spray

Posted by Animal Care Team on
absorbine blog, horse with flys in its eyes

Fly season is well underway in most of the country. While most barns have ways of mitigating the flies, it’s very easy for the problem to become more than just a slight annoyance. Choosing the best fly spray for your horse is often the first line of defense. With so many different products on the market, picking the right fly spray might seem like a tough choice. Here are six things to consider when picking the best fly spray for your horse or barn.

  1. Know your active ingredients. Active ingredients include insecticides, repellents and synergists. Insecticides are what kill the insects. Repellents stop bugs before they can even land on your hose. 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. You will want to look for a fly spray that has both.


  1. Understand the insecticides in the fly spray. The most common insecticides in equine fly sprays are pyrethrins and pyrethroids. Pyrethrins are extracted from certain types of chrysanthemums. They provide a very quick knockdown, killing the insects quickly. 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.


  1. What insects, other than flies, are you trying to repel? The best fly sprays not only kill and repel flies, they are also effective against gnats, ticks, and mosquitoes, too. Make sure to check the bottle to see which insects your fly spray will be effective against.


  1. Look at the percentages. If you’re examining two bottles of fly spray trying to figure out which one is more effective, the amount of active ingredients in each formula is important. Say Brand A contains .05% pyrethrins and Brand B contains .90% pyrethrins. That means there’s 18 times more active ingredient in Brand B. It’s easy to be misled by brands with big claims, but very low levels of active ingredients typically mean a lower price. With fly sprays, as with most things in life, you get what you pay for.


  1. Ready made vs. concentrate. If you’re buying fly spray for an entire barn, there are many formulas that come as concentrates that you can mix yourself and make larger quantities at a time. Make sure you understand how to mix the concentrate so your fly spray is the correct strength. A fly spray concentrate mixed in the wrong ratio can either not be effective or irritate the horse’s skin. If you are concerned about mixing incorrectly, there are plenty of fly spray formulas available that come ready to use. The ready to use sprays are already mixed in the correct ratios for optimum results every time.


  1. What about natural fly spray? There are many natural fly sprays on the market. These typically contain a combination of natural oils known to repel various insects. While these formulas often smell great, the oils in the natural fly spray only repel insects rather than killing them. This means that natural fly sprays are never going to be quite as effective as fly sprays with insecticides. This can confuse consumers who expect the natural sprays to yield the same results as the insecticide sprays.





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