The Why and How of Rotating Fly Sprays for Your Horse

It’s a simple truth: if you have horses, you’re going to be dealing with flies and insect pests at some level. Fly control will always be a management aspect of horse ownership.

Since fly control is ongoing year after year, how can you tilt the playing field against pests to put the odds in your favor?

Winning the battle against flies and pests requires a multi-stage approach. It also means using effective weapons.

Solution focused

We’re well into the 21st century, but the fact is most horse fly sprays use decades-old formulations.

Farnam recently tackled this issue head-on and created Endure® Gold Killer Fly & Mosquito Control (Endure® Gold), a next-generation insecticide/repellent fly spray with a synergistic combination of novel ingredients. It’s the first EPA-approved fly spray for horses with acetamiprid and etofenprox.

These two active ingredients--acetamiprid and etofenprox--set Endure® Gold apart from other products, making it the only equine fly spray formulated with these ingredients.

These insecticidal ingredients have different modes of action against pests.

“Even though both ingredients impact the insect’s nervous system, they attack different parts of the nervous system and both cause insect death after contact,” explains Chris Holderman, Ph.D., entomologist and senior manager of product development at Farnam's Research and Development facility in Dallas.

Combining acetamiprid and etofenprox in the formulation significantly boosts the product’s effectiveness, allowing horses to have lasting protection without daily application.

Depending on the species, Endure® Gold can last up to:

• 14 days - general flies (biting flies, stable flies, etc.)
• 10 days - house flies
• 21 days – horn flies
• 7 days - mosquitoes
• 14 days – biting midges

This broad-spectrum control offers day and night protection for peace of mind.

Mode of action

Equine fly sprays can be repellent and/or insecticidal. Repellent products are designed to just repel flies and pests, so they don’t bother the horse, while insecticides are specifically meant to kill pests that come in contact with the spray.

Depending on the formula, some horse fly sprays can both repel and kill pests. Endure® Gold is both repellent and insecticidal thanks to acetamiprid and etofenprox because these active ingredients both repel AND kill pests.

Horse fly sprays don’t all work the same way and can have different modes of action.

Some create a “bubble” of repellency protection around the horse which discourages flies from even landing. Other products are activated when flies land on the treated horse, causing the insects to be immediately repelled and fly away.

Both acetamiprid and etofenprox work when flies land on the sprayed horse. Flies absorb the chemicals through their feet. Although these active ingredients impact the insect nervous system in different ways, the end result is death to the insect.

But why create a new fly spray? Aren’t there plenty on the market already?

“We wanted to come up with a product that could be used rotationally to combat resistance and that’s what drove the development of Endure® Gold,” says Holderman. “When we started developing this formula, every product was pyrethroid based, and we know there is resistance to these ingredients when they are the only ones used.”

Endure® Gold is backed by an EPA-approved label and extensively tested to perform and deliver on those approved claims.

“Being EPA-registered means the product has to meet a lot of standards and be backed by intensive research--both on the environment and on the horse,” says Holderman.

Insect resistance

Many popular fly control products have limited modes of action that contribute to resistance.

When susceptible flies are killed by a product, the only flies that survive are the ones resistant to the ingredients in that product. Those remaining flies breed and produce more resistant flies, which continues the cycle of resistance.

When insects develop resistance to an active ingredient, the product is no longer as effective. You may have experienced this and wondered why a fly spray you’ve used for years no longer works as well as it did in the past. Insect resistance is often the reason.

Acetamiprid and etofenprox have never been used together in on-horse products before, so there are no resistance issues to worry about. Bottom line: flies and insect pests aren’t prepared for this powerful combination of ingredients.

“Etofenprox is exclusive to Farnam for equine use and Endure® Gold is the first product to use this ingredient on horses,” says Holderman.

Rotate products

The Farnam development team didn’t design Endure® Gold to be the only horse fly spray you’ll ever use. Rotating products is a concept that horse owners should adopt for the most effective protection.

As Holderman explains, the key to success is creating a fly control program, also known as an Integrated Pest Management (IPM) plan. Part of that strategy is using more than one product and rotating products through the season. You can significantly improve fly control by not using products with the same active ingredients and same mode of action all season long.

“Even within insecticides, you want to rotate between different modes of action to help prevent resistance,” says Holderman.

He recommends starting fly season with an on-horse repellent product that has worked well for the pest species you’re dealing with. As the season progresses, especially if the product you’re using doesn’t seem as effective, switch to an insecticide/repellent horse fly spray like Endure® Gold for the worst part of fly season. You can rotate back to the repellent product late in the season.

“It helps all the products work better when you’re not relying on just one mode of action or one active ingredient,” says Holderman.

Endure® Gold doesn’t have sweat-resistant properties, so you may opt to use a product like Endure® Sweat-Resistant Fly Spray for Horses when riding or training in hot weather.

Make a plan

Even with proven on-horse products to protect against flies, you need a multi-stage plan. That plan will vary somewhat depending on your location. For example, horse owners in New England will likely tweak their plan differently from horse owners in Arizona or Florida.

For starters, identify the flies and insect pests that are the main problem in your area. Knowing which species are the primary concern allows you to choose products that target these species and better manage them.

Timing and use of specific products may vary, but the basics are the same. An effective fly control plan should:

• Block: create an actual physical barrier (using fly masks like SuperMask, boots, sheets, as necessary) to keep flies and pests off the horse.
• Repel: use products that repel and kill flies and pests on the horse and in the environment.
• Reduce: decrease the fly population using SimpliFly® Feed-Thru Fly Control along with manure management and good housekeeping.

“Pest management is not a ‘one and done.’ All these activities add extra levels of control,” says Holderman. He emphasizes that there isn’t one single solution to controlling flies on the farm and around horses.

Starting your program early in the season will reduce the number of flies you have to deal with.

Don’t overlook the importance of manure management and good sanitation throughout the horse area. These practices aren’t high tech or complicated, but they are critical to keeping fly populations down.

Endure® Gold Killer Fly & Mosquito Control is in stores now, just in time for fly season. Adding Endure® Gold to your fly control plan will help you better protect your horse.