How Feed-Thru Fly Control Means Fewer Flies to Bother Your Horses

Wait a minute! How could we possibly have flies already? It was cold last week, and we've only had a few days of warmer weather.

Isn't it too early for flies? What's the deal?

House flies and stable flies are two species commonly found around horses. The fact is, both species can "overwinter," meaning they can survive winter in a developmental stage.

Overwintering is a key survival mechanism for some fly species. This explains why you can suddenly have an outbreak of flies annoying your horse well before summer officially arrives.

To understand how this happens—and how to avoid it going forward—let's look back in time to last fall.

Survival mode

Winter is around the corner, but female flies are still busy.

Meanwhile, you've been dumping your horse's manure in a pile behind the barn with plans to have it hauled off over the winter. You've also been feeding hay outside in some paddocks.

Without knowing it, you've played right into the fly reproductive cycle. And make no mistake, female flies will take advantage of this.

Manure and decaying organic matter, like decomposing hay and bedding, are optimal breeding sites for house flies and stable flies.

Females of both species automatically lay their eggs where they have the best chance for survival. This requires two things: moisture and warmth. Manure and decomposing hay and straw provide both.

Interestingly, these fly species have specific preferences.

"House flies like manure that is more freshly deposited. They will also use spilled feed or garbage. Stable flies like older aged manure and rotting hay, especially with manure mixed in," explains Casey White, Sr. Director of Technical Services & Innovation at Farnam's Research and Development facility in Dallas.

Because of these tendencies, both house flies and stables flies are considered "filth flies."

"Those female flies are opportunistic in what larval development sites they have easy access to," says White. "For stable flies, and other blood-feeding flies, they want a site close to the animals they are feeding on. House flies will be feeding around the horses and in close proximity, even though they don't require a blood meal to survive."

Egg-laying machines

To put things in perspective as to how prolific flies really are, here's a brief timeline. Remember, there are no "baby" flies. The fly that emerges from the pupae is already an adult.

• Adults can fly within 1 hour of emergence.
• Flies are ready to mate in 3 to 5 days.
• Mated females start laying eggs 5 to 8 days after emergence.
• One female house fly can lay up to 500 eggs in her lifetime in batches of 75 to 150 eggs.
• One female stable fly may lay up to 800 eggs in her lifetime in batches of 60 to 130 eggs.

Depending on environmental conditions, a house fly can go through its entire life cycle in 15 to 25 days but may live somewhat longer. A stable fly's average life cycle is typically about 28 days.

Even though flies have a short lifespan, they're primed to be incredibly efficient at reproduction.

"When you take into account a whole population of flies, at any given time there will be eggs being laid by multiple females in one area," notes White.

"Once females reach sexual maturity and are able to get eggs fertilized and ready to deposit, nothing will stop them from doing this," he adds. "Wind may keep them from doing so immediately, but they will lay their eggs in any site they instinctually identify as ideal for their larvae to develop."

Those eggs laid last fall at the end of fly season can survive by overwintering in manure piles in the pupal stage. Then early in the year after a brief period of warmer weather, adult flies emerge from those overwintering pupae.

If a spell of cold weather doesn't kill these new adults, they will mate and begin their reproductive cycle within days. And there you are, dealing with this season's fresh population of flies.

The good news is there are ways to make it difficult for eggs to overwinter, and to interrupt the life cycle of those flies that do emerge.

Interrupt the cycle

While you can't ensure that zero fly pupae will survive through overwintering, you can make it much more difficult.

This simply requires eliminating the manure pile and sites where hay and bedding are allowed to decompose.

Don't "stockpile" manure to be hauled off months later. Instead, have it removed weekly, or if you have the space, spread it on fields so it's completely broken up and dried out.

The same goes with old hay and bedding. Have it hauled away regularly and don't let it pile up. If you feed hay outside, change the feeding site regularly to avoid an accumulation of damp hay with manure mixed into it.

In addition to these straightforward management approaches to sanitation, you can use a feed-thru fly control product like Farnam^® SimpliFly.

"If you can make life difficult for the flies by removing larval development sites and using the feed–thru product, this makes it tough for the population to thrive and continue," says White. "Anything you can do to make their lives difficult will result in a reduced number of overall flies."

To have the greatest success with feed-thru fly control, you should start it early in the season before flies become a problem. Continue using it through fly season until cold weather returns in the fall. In warmer climates, you may want to use it year-round.

How the SimpliFly^® product works

The active ingredient in the SimpliFly® product works in the horse's manure, not inside his body. The product is safely formulated so that it's not absorbed by the equine digestive system but passes out in the manure.

You feed a small amount of the SimpliFly® product in your horse's ration each day based on how much he weighs. This automatically treats the horse's manure, setting up a fatal scenario for developing fly larvae.

Female house and stables flies lay their eggs in the treated manure. If the eggs don't remain moist, they won't hatch, which is why female flies naturally seek out the moisture of manure and damp rotting hay or straw.

In optimal conditions, the eggs hatch into first instar larvae within 12 to 24 hours. The larva begins to feed on the manure and develops through three instar stages in just under two weeks. The third instar larvae transform into pupae, which is where the new flies develop and emerge as adults.

So how does a feed-thru fly control product interrupt that life cycle?

During each short instar stage, the fly larvae must molt and reform their exoskeleton. This process requires chitin, which is a critical part of the exoskeleton.

The active ingredient in Farnam's SimpliFly® feed-thru fly control product is diflubenzuron, which is a "chitin synthesis inhibitor."

As White explains, without chitin, the larvae aren't able to form a functioning exoskeleton. Without that protective exoskeleton in place, they end up dying.

"Think of an astronaut; they have to have a sealed suit to go into outer space. If anything is broken on their suit, they are at risk," says White.

This is similar to what happens to the developing larvae when eggs are deposited in manure from horses treated with the SimpliFly® product.

"Most larvae won't even make it to the second instar stage because the manure they are in contains enough of the active ingredient to interrupt their development," notes White.

The fly population takes a serious hit when larvae can't develop, and the lifecycle is interrupted. When horses are fed the correct amount of the SimpliFly® product, this occurs early in the process.

All it takes is daily use of the feed-thru fly control product until cold weather returns.

In case you're wondering, there's nothing about manure from a horse being fed the SimpliFly^® product that will warn the female fly this isn't a good place to lay her eggs.

"This 'stealth component' means the female looking to deposit eggs will still lay eggs in that manure not knowing it has the insect growth regulator in it," says White.

Ease of use

The convenience of a feed-thru fly control product is that it works continually as long as you're feeding it.

So long as a horse is fed the feed-thru fly control product every day during fly season, every time a house fly or stable fly lays eggs in that treated manure, the developing larvae will be exposed to the active ingredient and will not able to complete development.

"This product is a useful tool because it's being deposited by the horses themselves in the very areas where flies will be laying eggs," says White. "It's doing its job even when you're not around."