Release Fly Parasites Now

Although a fly?s actual life span is short, no more than a month, their prolific breeding makes their presence seem endless. The biting stable fly may lay 10 to 12 batches of 40 to 80 eggs during her short lifetime. We’re willing to try almost anything to get some relief for our horses from the biting pests, and those of us who have tried fly parasites are convinced they are the best method.

Of course, good manure management is crucial to fly control, but many other factors are involved in controlling the reproduction of these winged monsters. In fact, it’s not just manure.

A study at Texas A&M demonstrated that a million biting stable flies could develop in the residue of one round bale of hay.? Other guilty locations are lawn clippings, moist compost, mulch and gardens. Standing water is great for breeding mosquitoes, as you know. But you may not have been aware that horse- and deer-fly larvae favor shallow water and wet ground, too. That mud hole by the water trough might be nearly perfect for them.

FIELD TRIAL. Last summer, a group of our testers, all living in the same general area in New York, decided to conduct their own field trial using Fly Predators, a specific brand of fly parasites from Spalding Labs (, 800-706-3116). We found the results so interesting that we wanted to share it with our readers, despite it not being a head-to-head comparison of fly parasites.

Several farms used Fly Predators to control nuisance flies, while others used traditional methods for a comparison. With this method, they decided, they couldn?t pass off a ?quiet? fly day as being solely weather-related, since they could compare with the activity on an unprotected farm.

Two farms with adjoining property lines showed a dramatic difference. The horses were actually a ?crow?s mile? apart, but the ones with the predators defending them had hardly a fly problem all summer, while the other horses were standing in the darkest part of their run-in shed, still stomping and swishing their tails.

All barns were kept clean, and some farms picked manure up out of their paddocks, while others didn’t. The fly parasites worked as well in either environment.? However, the establishments using more diligent manure management seemed to have better control. There also appeared to be a noticeable decrease in the flies that were not listed as being affected by the fly parasites.

One stable that kept four acres clean around the barn, run-in and riding area but did nothing with the manure in their 12-acre pasture had fantastic results.? (This farm is a half mile from a small cattle operation and adjoins a nature conservancy swamp, both prime breeding grounds.)? They were virtually fly-free all summer, noticing even a strong decrease in face, deer, horse and bot flies.

This stable used a small bag of parasites, designated for one to five horses, and sprinkled the predators on the manure piles. They also made a loop through the pasture, placing parasites on fresh manure in the rough areas.

ADDING BUGS. Our testers estimated they used 75% less fly spray than in previous years.? One user noted the difference in not having used two gallons of concentrate, but only two pints of wipe-on.

The price for a season?s supply of parasites is about the cost of a gallon of concentrate, and it’s a lot less work (one packet of parasites will do 1 to 5 horses and costs $18.45; the number of packets you’ll need for the season varies with your location). We found it takes only minutes to spread the parasites every three weeks.

When you receive a packet of? ?anti-fly army,?? you’ll see that it’s packed by volume and weight. Once the flies were released, they were never seen again.

The Fly Predators consist of several species, all bite-less and stingless. They won?t harm bees, and the only way you’ll see them is if you take a magnifying glass and look for them crawling around the manure.

they’re easy to use. When the shipment arrives, you place the packet in a warm place. In cooler spring weather, they hatched best if brought inside, but during the summer they did fine in the tack room. When you let them go, they just fall to the manure along with the shavings they’re packed in.? it’s as easy as sprinkling bird seed.

The farms gradually used less sprays and fewer traps. A few farms found they no longer needed fly masks either, although we still recommend using them, especially since they?ll protect against the few wayward insects that aren?t bothered by fly parasites and protect your horse’s eyes from debris.

You can use fly sprays on your horse when needed. However, you can’t use them over or close to the areas where the predators are released or you will destroy them. Fly traps have no effect on them as the predators never leave the manure, except to travel to the next pile.? Because flies breed much faster than the predators, you will need to add reinforcements every few weeks.

BOTTOM LINE. If you try the bugs, remember that the parasites only stop the eggs from hatching. They don’t attack adult flies.? Any flies you let develop will have to run their life span or be trapped. We recommend trying fly parasites. it’s natural, inexpensive and easy. Judging whether they work or not is as simple as looking at your horse during a summer day.

Fly Parasite Manufacturers

The companies listed here do not necessarily produce exactly the same fly parasites as one another. We’ve learned that some companies, such as Spalding Labs, even have bugs specific only to them.

You may need to experiment yourself to determine what works best for you. Ask your seller, including the ones listed here, what species you are getting in the packet, so you know if you’re getting the same insects or not.

Fly Predators, Spalding Labs,, 800-706-3116

Fly Eliminators, Arbico,, 800-827-2847

Fly Raptors Source Ecological,, 800-380-3560

Bug Logical Control Systems,, 520-298-4400

IPM Labs,, 800-441-2847

?Points To Remember

  • ?These are parasites that kill kill immature flies by laying their eggs in the fly pupae (cocoon).? They do not affect existing adult flies.
  • ?Biting flies are different than house flies. you’ll normally find house flies on your horse’s face, while the biting flies (seeking blood) go to the flanks and legs.
  • ?You need to understand where the flies are coming from in order to destroy them. House flies like manure, while biting flies will breed in compost, grass cuttings, and low wet spots.
  • ?Flies won?t breed in dry manure, but wet or damp manure is pretty much a fly factory.
  • ?Parasites are a preventative measure. The sooner you start the better, but if the biting and house flies are already out and about, you’ll need to wait through their life cycle before you see the decrease. it’s not too late to start now, but timing is everything.

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