Monday, April 11, 2022

Fly Control with Fly Parasites

Close-up of the face of a housefly.
My mother used to say that nothing was certain but death and taxes. I’d like to amend that statement to include Arizona summer heat and summertime flies for everyone. We are all acutely aware of how annoying, disgusting  and relentless flies are and  keeping them away is never 100% effective. However, by introducing fly parasites into your world, you can make a powerful dent in their population. Here at ARBICO we pioneered the use of these invaluable insects some 40-plus years ago when the whole idea of using insects to kill insects sounded like science fiction to most people. Fast forward to 2022 and we are still raising and selling  Fly Eliminators® and  have greatly expanded our inventory of "good bugs" to include predators for the most common garden pests.

A female preparing to pierce a dark brown pupa. In the upper left hand corner with a line marked 1.5 cm that has a line under it. This is to show scale.
Fly parasites are non-stinging, gnat-sized wasps that use fly pupae as both a convenient sheltering place for their eggs as well as a food source for the eggs as they grow. Parasitoid wasps (aka parasitic wasps) are common in the insect world, but these particular ones are host-specific to flies. There are several species of fly parasites that are native to North America, but they are not usually present in large enough numbers to affect the fly population (which reproduces quicker and in larger numbers). The Fly Eliminators® we sell here at ARBICO are a proprietary mix of several species of these wasps, because diversity is beneficial in all parts of our world.

A picture showing the lifecycle of the fly parasite, beginning with the adult fly in the 7 o'clock position.
The world of parasitoid wasps is a ruthless and gruesome one that most people are never aware of, even though it’s happening all around us. This is because the wasps are mostly tiny insects and much of the activity is out of sight underground or out of sight within pupae. In addition, many parasitoid wasps are nocturnal. Fly parasites fall into all these categories. The females venture out under the cover of darkness and fly about a foot off the ground in search of fly pupae. Once they find the pupae, the wasp tears a hole in it and deposits as many as 10 eggs inside. She will keep moving through the fly larvae until all her eggs are gone. She can eliminate up to 100 fly pupae in her very short lifetime. As her eggs develop they will feed on the immature fly. This will eventually kill the fly, but not until the developing parasite has gleaned as much nutrition as it needs from the fly. So, they feed on it while it’s still alive in there – ruthless and gruesome.
Adult parasite emerging from brown pupa

Dark brown pupae showing the holes that parasites made upon emerging.Fly parasites hatch out of their pupae in 17-21 days, depending on temperature and other environmental factors. Flies, on the other hand, can lay five to six batches of eggs in a month (more on their lifespan here). Due to this disparity, in order to gain control of the fly situation you will need to regularly introduce the parasites to the area where flies are breeding – and in larger numbers than would normally be there. That way, there will always be a wasp ready to parasitize the next batch of fly eggs. That being said, the reproductive power of flies is such that parasites can control flies, but can’t eradicate them completely.

It’s important to remember that fly parasites are only effective against larval flies. For adult flies, you will need another source of fly control. It's also important to take measures to control or eliminate fly-friendly habitats like manure and wet areas. Check out our 4-Step Fly Control page for more information.

Close-up of the face of a horse with flies buzzing around it
Will they sting me or my animals? Or swarm?

In short, absolutely not. They are too small to do harm to anything but fly pupae. Plus, and this is a big one, they do not have stingers. Although the females have an ovipositor that could conceivably be mistaken for one. These are solitary insects; they mate, lay eggs and die. That’s it. They do not form social communities like colonies or nests that need to be protected or moved (the usual reasons for swarming).

Will they get rid of all the flies? 

A chart showing 22 different species of flies

Fly parasites are only interested in filth-breeding flies – other flies will not be affected by these wasps. Simply put, filth flies breed and feed in manure, rotting organic matter and other sweet or smelly or sweet and smelly areas. House flies are filth flies, as are stable flies. However, the female stable flies are also blood feeders (they need it to produce viable eggs). Stable flies may be controlled by fly parasites, but it isn’t very effective for them. So, a good rule of thumb is that if flies are biting you or your animals (and drawing blood), the parasites are not a good control choice. Here's a blog I wrote last year on this subject.

Would I need specific equipment to use these beneficial insects?

Brown fly pupa with white sawdust .
Nope – fly parasites are sold commercially while they are still cocooned in the fly pupae. They are about the size of a grain of rice an usually mixed with sawdust. All you need to do is go out to where your problem flies are, kick up a little dirt, sprinkle some pupae in and cover them over lightly with dirt. You don’t want to bury them, just cover them enough so birds won’t easily find them (these cocoons are quite the treat for both wild and domestic birds).If you don’t want to touch the cocoons, you can sprinkle them directly out of the package. An even distribution will cover more ground but is not strictly necessary.

Is it safe to use these around livestock and pets?

Close-up of a cow's face with flies buzzing all around it.
As I mentioned before, these insects do not bite or sting and are only interested in fly pupa. They will not harm domestic animals. We get calls fairly often about dogs getting ahold of a bag and eating them; although we encourage you to keep them away from pets, a dog can eat a bagful with no serious effects .

We have several pages on our site about how to purchase and use Fly Eliminators. I encourage you to peruse them at your leisure for more information. Or call one of our specialists at 800-827-2847; they have a wealth of information to share.

A small skeleton tapping a fly on its head. Take Care

Submitted by Pam

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