Beneficial Insects: Good-Buys for Flies

Spiders are not the only beneficial insects.

Wouldn't you love to say good-bye to biting, stinging, pesty flies? And mean it? Better yet, wouldn't you love to never have to say hello to them? I would. Flies are a part of the horse world - where there is a horse, there is manure, and where there are horses and manure, there are flies. Flies such as house flies, horn flies, stable flies, greenhead flies, deer flies, snipe flies, black flies and whatever other unfavorites you can think of breed in the manure and feed on the horse's (and your) blood. Flies are annoying and can cause many problems. There is no escaping them - or is there?

You probably already know that: 1. Fly sprays are temporary. 2. As soon as your horse is sprayed and wears his fly barrier the flies attack you instead. 3. Many fly sprays can be harsh, irritating, and even toxic to your horse, and to you. 4. Stall and barn chemical misters and floor granules are toxic and environmentally unsafe, and flies can even become resistant to the chemicals. 5. Fly masks get muddy, torn, lost, and may chafe the horse. 6. Fly traps are wonderful until they need to be emptied (yuk!). 7. Fly paper snags more mane, tail, and human hair than flies (ever see your horse wearing one?). 8. Good sanitation practices help greatly, but who can patrol the pasture 24 hours a day? 9. All of the above take a big chunk out of riding time.

Unfortunately, pesticides are probably the most commonly used method of fly control. We spray those nasty flies - knock 'em down, poison 'em, kill 'em - it's easy. But does it really work? Pesticides are not only toxic, they are also only partially effective. In fact, they can contribute to a worse fly problem. They may work at first on adult pest flies, but within a few days a new generation of flies will emerge, because pesticides are not effective against the pest fly's immature stages so the reproductive cycle is not affected. Because pest flies rapidly reproduce, they rapidly develop resistance to pesticides, requiring the continual use of more and harsher chemicals.

Have you ever noticed how, when the buzzing bugs start appearing in the spring, the spiders and their webs start appearing too? And why is that? Because spiders eat bugs. Spiders are a horseman's friends. But how many of us encourage spider webs in our homes and barns? Not many. Spiders are effective, and they are not toxic to the environment. They are beneficial insects, but they are not the only beneficial insects - there are a few more worth becoming familiar with.

What are beneficial insects? Beneficial insects are friendly little bugs that help the horseman, farmer, gardener, and the animals. They are natural enemies to many known pests. Ladybugs and lacewings, for example, are two that help the gardener and farmer by eating the bugs and worms that devour their gardens, plants, and trees. For animal farmers and horsemen, there are fly parasites, dung flies, and dung beetles.

Fly parasites

Dung flies, golden and fuzzy, are among the beneficial insects that help reduce the pest fly population.

Fly parasites are tiny, wasp-like insects that eat fly pupae (the developing fly). Though the tiny pupae eaters are members of the wasp family, they don't sting or bite. In the undisturbed natural environment, this natural enemy of the pest fly keeps the fly population in check without any of the dangers of pesticides. Muscidifurax raptor and Spalangia endius, Spalangia cameroni, Muscidifurax zaraptor, and Muscidifurax raptorellus as they are called, are members of the Chalcididae family, a family that contains many of the world's beneficial insects.

These insects are friendly fellows that destroy the pest flies in the pupal stage by eating the pupae. Or they may lay their eggs inside the pupae as part of their own reproductive cycle, and when the little parasites' eggs hatch inside, they eat the fly pupae. They emerge 30 days later as adult fly parasites, ready to mate and start the cycle over again. That is how they eliminate flies, and they self-propagate in the process. Neat, clean, effective, before the fly can become an adult.

In fact, that is how they are shipped to arrive at your farm ready for application - inside the pupae of the pest flies. Just sprinkle them on or near the manure and other pest fly breeding sites and they will emerge and get to work. And they search for fly pupae, so they will find them wherever they are. Fly parasites live on manure and other fly-breeding areas to destroy the pest flies at their source, never becoming pests themselves, and they are specific to flies, never attacking anything else. They are very small and hard to see, and they are generally more active at night.

The female fly predator's life span ranges from two weeks to six months, long enough to deposit all of her 200 to 300 eggs. (The pest fly lives about 30 days and the female fly can lay up to 900 eggs.) When the pest fly population is under control and there are no pest fly hosts, the female fly predator will reabsorb her own eggs as a source of nourishment to enable her to live up to a month or so longer while waiting for other pest flies to come along and lay their eggs.

Although fly parasites are experts at eliminating the earlier stage of the pest fly, they cannot do anything to rid us of the existing adult flies. So while we are waiting for the adult fly's life span to come to an end, there may be a temporary need for compatible methods of controlling the adult population until the numbers are reduced through pupal elimination. Do not use pesticides, however, as these will destroy the fly parasites. The use of fly traps is recommended instead as it is a safe method. Becoming fly-free is a gradual process if the fly population is already abundant; not all flies will disappear immediately.

The number of fly parasites needed for your individual situation depends on the size of your operation, the number of animals, the severity of the current fly problem, your location in reference to other farms, and the results you want to achieve. Fly parasites will self-propagate in the process of destroying pest flies, but may be unable to reproduce quickly enough to control huge numbers of pest flies. The pest flies can travel up to a half a mile a day, which means there will always be pest flies migrating in from neighboring areas whereas fly parasites can only disperse themselves a few hundred feet from where they have emerged.

Pest flies reproduce more readily than the fly parasites, so applying adequate numbers of parasites when needed is important to achieve and maintain control. Monthly applications may be advised throughout the entire fly season to keep the fly parasite population heavy enough to get and keep things under control.

It is certainly easier to prevent a pest fly problem than it is to get rid of one once it is established, and although control can be achieved at anytime of the year, it is best to start a biological fly control program as early in the spring or summer as possible, or when the first flies begin to appear. Monthly applications can be continued throughout the fly season until the first fall frost.

Dung flies

Naturally occurring dung flies. The adults prey on house flies and other adult insects; the larvae feed on dung.

If you ever walk past the manure pile or a wheelbarrow full of manure and a swarm of golden, fuzzy, sometimes red-eyed, bee-like insects are swarming around the manure, don't disturb them! They are dung flies, beneficial insects that prey on pest flies and other adult insects. They seek out manure, lay their eggs in it and the larvae will tunnel down into it feeding on the dung as they go. Dung flies may resemble bees in appearance, but they leave man and animal alone. And they are not toxic to the environment.

Dung beetles

Dung beetles are hard-working beneficial insects that eat and break down manure. Dung beetles, Scarabaeidae, were worshipped by the Egyptians - the scarab beetle, the mystical religious symbol of the ancient Egyptians, is a dung beetle. Dung beetle history extends back to the early Jurassic period.

The dung beetles have tough, biting jaws to squeeze and suck the juice from manure, but they don't bite and suck on flesh. Dung, along with everything else that lives in it, including fly larvae, is the major food of the dung beetle. Adult dung beetles eat the nutrient-rich liquid of fresh dung, which contains microorganisms from the intestines of the animal, while immature dung beetles feed on the undigested plant fiber in the dung. 

Most dung beetles make tiny tunnels in the soil. The beetles break up the dung piles, shape the manure into small, smooth balls, roll them across the ground for several feet, and carry them down into their tunnels. The female lays her eggs in the dung balls.

Dung beetles also promote pasture quality. When they make their tunnels, water and air can permeate deep into the soil. Their activity speeds up the rate of dung degradation and incorporation back into the soil. Dung gets recycled into and spread evenly throughout the soil as an excellent fertilizer, and all that is left is refreshed, fertilized soil. Less exposed manure also results in fewer flies.

Dung beetles are not well known to the United States. They are more readily found in Africa, Australia and Mexico. There was a time when Australia had a dung accumulation problem because there were few native dung beetles and many imported cattle. When the cattle were imported from Europe, they arrived without their dung beetles and the native beetles could not handle the excess manure. (Kangaroo manure is of much lesser quantity than cow manure.) Years later, after successful importing of dung beetles, the manure problem started disappearing. Hawaii is another area where beetles have been imported; Mexican beetles have been successfully introduced there.

Dung beetles may also be a major source of food for birds and small mammals. Some dung beetles can also fly. There don't seem to be any disadvantages to dung beetles!

Other common-sense fly discouragers

An adult fly parasite and the fly pupa from which it recently emerged.

Man's desire to concentrate animals in small areas upsets the natural balance among pest flies and their predators. Beneficial insects naturally occur in small numbers, and letting nature take its course would be acceptable under most natural conditions. But where there is a dense population of animals, there will be a dense population of pest flies.

Good farm management practices such as the following can help keep pest fly numbers down.

Stop water leaks promptly; moisture promotes fly breeding.

Keep feed storage areas clean; spilled feed can be an attractive breeding site.

Ventilate areas where manure collects; dry manure means less fly breeding.

Dry manure also means a more active and effective population of natural predators and parasites; where manure accumulates and stays reasonably dry, there will be an abundance of mites and beetles that prey on pest flies and use them for their own reproduction.

Try something different this year - try friendly, beneficial insects. Beneficial insects can provide efficient and environmentally safe pest management. The cost is minimal in comparison to what can be spent on conventional methods, and the results are much better. There are even predators available for fleas - naturally occurring, insect-killing, beneficial nematodes that prey on the pre-adult stages of fleas and several common garden pests. Give all your animals the benefit of a highly effective and environmentally safe method of pest control - beneficial insects.


For more information or to purchase beneficial insects:

The beneficial predators will appear on the sides of the package as they begin to emerge from the fly larvae casings. When several are seen, they are ready to be distributed.

A-1 Unique Insect Control

5504 Sperry Drive

Citrus Heights, CA 95621



Spalding Laboratories

760 Printz Road

Arroyo Grande, CA 93420



The Natural Gardener/Gardenville of Austin

8648 Old Bee Caves Road

Austin, TX  78735



Beneficial Insectary

14751 Oak Run Rd.

Oak Run, CA 96069-9565



Gardens Alive!

5100 Schenley Place

Lawrenceburg, IN 47025




100 Countryside Dr.

Bellerville, WI 53508



Harmony Farm Supply

PO Box 460

Graton, CA 95444




PO Box 25845 (mailing address)

8765 Vallmer Rd.

Colorado Springs, CO 80936




333 Ohme Gardens Rd.

Wenatchee, WA 98801



Natural Farm Store

Route 2, Box 201A

4360 Spencer Rd. SE

Kalkaska, MI 49646



Necessary Trading Co.

PO Box 305 (mailing address)

8311 Salem Ave.

New Castle, VA 24127



Peaceful Valley Farm Supply

PO Box 2209

Grass Valley, CA 95945