Mist Away Those Flies

If you’re trying to limit fly populations in a large barn, or have a fly population so pesky that you dread summer, an automatic fly-misting system may help. Misters do kill a lot of insects with each spray.

An automatic fly mister is a central barn-ceiling unit that sprays fly repellent and insecticide throughout a barn via tubing and nozzles. Misters are powered by electricity. A drum full of insecticide is set up in your stable and connected to hoses overhead.

The hoses allow the insecticide to flow to the nozzles that dispense it at regular intervals. A float system shuts off the system when the drum is empty so that the pump doesn’t run without fluid. Anyone who has been in a barn outfitted with an automatic system is used to the quiet “whoosh” of the mister that signifies that it’s spraying. It’s much like the water misters in the produce department of a grocery store.

Misters provide a hands-off way to control insects beyond the ones actually on horses and minimize the need for using fly sprays in the barn. Since bottled fly sprays are typically higher concentrations of insecticide than that in misting systems, many people prefer the misting spray rather than spraying from bottles by hand.

Most misters use a vane pump, which looks something like a fan blade. The vanes (spire or rod-like objects) are placed in slots in the rotor. As the rotor spins, centrifugal force pushes the vanes out to the casing, where they trap and propel fluid. When the vanes reach the return side, they are forced back into the rotor by the casing. The fluid escapes through a channel, and the whole cycle begins again.

You can use a timer to set the mister according to the season, location and how your barn is used. For example, if the horses are out all day and the barn is cleaned then, you could run the mister before bringing in the horses. Or an automatic mister can be set to go off at sunrise, when the flies begin to emerge. After that, hourly spraying for about a minute can keep the pest population down during the day. But don’t set it to go off directly at feeding time.

The insecticides used in the systems vary by manufacturer, but many use pyrethrum, which is made from chrysanthemums. There are synthetic options as well — one common one is called Permethrin — and they serve much the same function. John Marsh, of Pro-Tech, says synthetics don’t work as well as natural products because insects can adapt to them. He says the natural variations in chrysanthemum-based insecticides keep insect populations from becoming immune.

Other options include odor reducers that can be put in the tank with the insecticides to keep the characteristic astringent smell down. Manufacturers recommend not using anything in your mister other than products approved for use in that overhead system. Simply loading your unit with generic citronella, for example, may gum the system and clog nozzles. You may save money in the long run by paying more up front but avoiding service charges in the future.

Parts And Pieces
Different misters can handle different amounts of nozzles. Some systems come with nozzles, and with some you have to order nozzles separately. The number of nozzles you need depends upon your fly problem and the area you’re trying to control.

One standard MT Heavy Duty Mister system, for example, can handle up to 60 nozzles. The optional, extra heavy-duty system can handle up to 250 nozzles.

Larry Spears of Pyranha suggests no more than 70 nozzles for a standard, 55-gallon drum system, and no more than 30 for a 30-gallon drum.

We found the fly-misting systems were pretty similar to one another. Most have a 1/3 HP motor and 55-gallon drum. Smaller units vary more. Automist has a 30-gallon-drum system, and the Mosquito Terminator Compact Mister has a 14-gallon drum, which is normally used in dog kennels but may work for a two- or three-stall barn. Shut-off systems are important, because if the system runs without liquid, the motor will be damaged.

Variables include the timers, which are manual or digital. In general, we like to keep things simple. We’d choose a manual timer like those sold by Pyrahna and Shoo-fly, which will be less trouble to reset in case of a power surge or outage and less frustrating in general. If you find programming a VCR a challenge, you’ll probably want to stay away from a digital timer.

Automist systems have the option of a wireless remote-control timer, which is convenient, especially if you have stashed your main unit somewhere out of reach, like a hayloft, and don’t want to climb a ladder to reset the timer.

Make things easier for yourself by putting the drum where you can easily access it for refilling and maintenance. Some good choices are behind the feed-room or tack-room door, which puts it out of the way yet leaves it easy to get to.

When deciding where to put nozzles, becoming something of an entomologist can help. Standard placement is one nozzle over each stall, and then one at each end of the barn, but consider where flies congregate in your barn. Flies usually have a naptime where they all come together, so you’ll want to point a nozzle there.

When choosing where to place the nozzles, we’d recommend avoiding the tack or feed room because of the possibility of tubing breaking or shrinking and insecticide wetting feed or staining saddles. We’d also try to set up stalls so the mist isn’t directly over the hay corner/rack, water bucket or feed tub.

We recommend that you buy a system with a dust cover. They’re standard on most machines and are important because if dust gets in the drum, then in a nozzle, air can suck in. Then the system won’t pressurize, which means you have to drain the system and/or clean all the nozzles, a time-consuming chore.

Cleaning the unit’s suction filter with water can help keep things running smoothly. Winterizing is also important. Diane Goodrich of Shoo-fly says that you can use motor-home antifreeze. Don’t just drain the lines, since there will likely still be fluid in the pump and nozzles that will freeze in cold climates and gum up in warmer areas. And when the weather gets warmer, clean the system before trying to use it. Inspect your nozzles frequently and replace them as necessary, because a cracked one will allow dust and air into the system.

Misting systems can require frequent maintenance. Some people don’t like the insecticide smell, or simply don’t like to breathe it in, and may complain about it being automatically dispensed.

Also, remember that horses need time to get used to misting systems. The first time they hear the noise, they may panic. Consider bringing in two horses at a time to get used to the system, and calm will prevail as herd mates realize that the misting system won’t hurt them.

Bottom Line
You can’t go wrong with any of the systems in our chart. The differences are really minor, and all appear to be sturdy machines backed by strong reputations.

However, we lean toward the systems that let us choose our own nozzles. We also like dust covers and Automist’s gasket door to protect machinery, which is a nice double-safety measure, as is the Mosquito Terminator’s cordura timer cover. Varying drum sizes are also a good option, depending upon the size of your barn.

Because pricing can often vary from dealer to dealer, check with the company to find out who retails locally. California requires registration fees and more insurance, for example, so prices on the same system can vary by locale. Consumers should plan to spend about $3 to $4 per nozzle per month in insecticide, although this, too, may vary widely by region.

Finally, we advise you to compare insecticide costs and delivery charges when you make your choice. A seemingly lower-cost misting unit could become more expensive if the insecticide it uses is difficult to get or expensive to use.

Also With This Article
Click here to view “Smart Misters.”
Click here to view “Fly Mister Systems.”

What did you think of this article?

Thank you for your feedback!