What Are Fly Predators?
When I think of fly predators, I instinctually imagine my mom running around the house, hell-bent on eliminating the current fly infestation with an arsenal of traps, sprays, swatters, and electric zappers.
And admittedly…this is definitely the person I’ve become over the last few years.
Although somewhat effective, this is not the type of fly predator you need at your homestead or farm.
To adequately control the pest fly population, you need a fly predator that is evolutionarily bred to eliminate flies. The best “tool” for the job is called a parasitoid, or Muscidifurax raptor, a parasitic wasp species that kills flies before they can develop into an adult.
In this article, I will take a deep dive into fly predators. I’ll discuss what they are, how they operate, and how you can harness fly predators as a natural, chemical-free mitigation tactic for the nuisance flies on your property.
The importance of managing fly populations on your farm
The epitome fly predator- Muscidifurax raptor
Muscidifurax raptor life cycle
Using predator flies on your farm- where, how much, and how often
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Why Is Managing Flies Important?
Before discussing more about predator flies, it’s important to understand why you might need them in the first place. Unfortunately, nuisance flies on your farm are inevitable. They come with the territory. However, too many flies can begin to cause issues.
Out-of-control fly populations on farms can increase disease transmission. In addition, fly populations can cause different behaviors in your animals, some of which can decrease production, for example, with dairy cows. In addition, large populations of flies on the farm are a nuisance to us humans. And they can bite!
For those reasons, managing flies on your farm is important. Oftentimes times, you can manage nuisance fly populations on your farm through hygienic farming practices. But sometimes, the flies go beyond your control. That’s when you might deploy fly predators as a management tactic.
What Are Fly Predators?
In this context, I’m not talking about natural predators that feed on flies, like frogs. Above, I introduced a specific type of insect whose sole purpose in life is to disrupt the reproduction cycle of nuisance flies like the ones constantly bothering your horses and cattle.
Muscidifurax raptor is a member of the Pteromalidae family. It’s just one wasp species of approximately 3,600 included in the family that is known as insect, arachnid, or plant parasitoids. Parasitoids are a type of parasitic wasp that kills fly populations before they can develop into adults. In doing so, parasitoids act as natural biological control agents of insect pests.
Muscidifurax raptor is one of the most commonly occurring fly predators. It can be found in North, Central, and South America, Africa, the Caribbean, the Middle East, Europe, Australia, and many Pacific Islands. In particular, it's common on sheep, dairy, and beef cattle farms. In addition, it is common on caged poultry farms. Typically, it’s naturally found in livestock straw and feed.
Included in the Muscidifurax genus are two other wasp species, Muscidifurax raptorellus, and Muscidifurax zaraptor. Each species of predator fly differs in behavior, where they inhabit, and the hosts they choose to feed on. However, all three are extremely effective at controlling populations of nuisance flies.
How Do Fly Predators Work?
As I stated above, there are thousands of different species of fly predators, each with their own intricacies. However, to keep things simple, I’ll continue discussing Muscidifurax raptor as the epitome of how fly predators operate.
An adult parasitoid is a tiny black wasp. It’s only visible to humans in its adult stage because during its development as an egg, larva, and pupa, it remains inside the fly puparium encapsulated in a cocoon.
While inside the host fly puparium, the fly predator undergoes a metamorphosis. It hatches from an egg, develops through multiple stages of instars and pupates, and then emerges as an adult. The length of this development cycle depends on temperature. At 26°C, it takes 17-22 days, and at 27.8°C it takes 13-15 days.
After a female Muscidifurax raptor emerges from the host fly’s puparium, it immediately begins its mating and oviposition processes. While looking for a host, a female goes through four distinct phases– finding the host area, locating a host pupa, drumming and drilling, and feeding. This entire process can take 10-15 minutes.
Fly predators locate their hosts in the manure piles of animals. Once they’ve found a potential fly pupa to infest, they drum along the pupa with their antennae. If the pupa is dead or has already been parasitized, they move on to the next best option.
Once a female finds a suitable host, they drills through the surface of the puparium, inserting her ovipositor and stinging the fly pupa inside. This process kills the fly. Afterward, the female parasitoid uses its ovipositor to feed on the fly pupae by sucking its blood. After feeding, the female deposits a single egg on the surface of the puparium.
With ideal conditions, a female Muscidifurax raptor can parasitize 13 fly pupae per day and about 100 during her life span. After she lays the egg, the larva hatches two or three days later. It completes three larvae instars over a 10-13 day period. Then, an 8-12 day pupal stage, after which an adult emergence occurs about three weeks after the original egg was laid. Male parasitoids emerge prior to females. Female parasitoids can reproduce both sexually and asexually. After sexual reproduction, only male offspring are produced. From there, the cycle continues.
How Many Fly Predators Do You Need?
It’s most common to purchase fly predators like Muscidifurax raptor in large shipments. Usually, fly predators are mailed to you as parasitized fly pupae. It's common for the pupae to be sent in plastic bags filled with sawdust or wood shavings. The size of the shipments and quantity of fly predators per package will depend on the manufacturer you’re choosing to purchase from.
The number of fly predators you will need depends on a variety of factors. Specifically, the number of fly predators you deploy will depend on the severity of the problem, the number of animals you own, your manure management, and the size and condition of your stables or property.
To release your predator flies, make a small hole in the ground. Deposit your fly predators into the hole and cover it with straw, dirt, or sawdust. Depending on the severity of the area, deposit as little as a teaspoon or as much as a handful.
How to Measure:
1/20 of a colony: 500
3 tablespoons
1/10 of a colony: 1,000
3 ounce cup
¼ of a colony: 2,500
1 cup
½ of a colony: 5,000
2 cups
1 entire colony: 10,000
4 cups
Spalding Labs has a super helpful webpage where you can plug in your location, and the number and type of animals you have on your property to get an estimated amount of predator flies.
When Should You Release Fly Predators?
When you release parasitic wasps on your property mainly depends on your geographic location and local climate. If you live in an area with a milder climate where nuisance flies survive all year, you can start anytime. However, if you live in an area that experiences winter, you will need to focus your attention on the spring and summer months.
Take a look at this table for a rough estimate of when you should release fly predators to manage nuisance flies. You’ll notice I recommend almost year-round fly predator application in the southern tier of the United States while in the northern tier, I only recommend releasing flies during a portion of the year.
Zone A, Southern US Climates: Start: Mid-February, End: Mid-November
Zone B, Middle US Climates: Start: Mid-March, End: Mid-October
Zone C, Northern US Climates: Start: Mid-April, End: Mid-September
Remember– although these timing recommendations are helpful, do your best to make the most appropriate decision for your specific circumstances.
What is the Best Place to Put Fly Predators?
The application of predator flies is simple. After you purchase your fly predators or receive a shipment in the mail, you will want to strategically locate them around your property to be the most effective. Location is important because, typically, fly predators travel 90-150 feet in search of hosts.
When you are applying your fly predators, focus on as many problematic “hot spots” as possible. Over time, repeat your release methods in slightly different areas around your property.
Urination and Manure Areas:
In kennels and coops
Around manure piles, pits, carts, and bins
Around paddocks, corrals, and fence lines
Inside stables, stalls, barns, loafing sheds, and hospital pens
Feeding and Watering Areas:
Below water troughs, feeding tubs, and near buckets, barrels, and other watering devices
Around bathing areas, run-off areas, and drainages
Areas where straw and feed have decomposed
Wherever leakage or spilling occurs
Other Areas Where Flies Can Breed:
Alongside your garbage cans
Around your compost piles
In the family garden (especially if the garden gets flooded)
Are Fly Predators Invasive?
According to the United States Department of Agriculture, an invasive species is understood as “a non-native (or alien) to the ecosystem under consideration whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”
Species of fly predators like Muscidifurax raptor have been found naturally on the North American continent. In addition, they are not harmful to economic, environmental, or human health. Therefore, they are not generally understood as invasive species.
How Long Do Fly Predators Live?
The lifespan of fly predators depends greatly on temperature. Once an adult, fly predators typically survive for 26 days, depending on temperature. As the temperature increases, the life span of predator flies decreases(15.5°C to 32°C).
When Are Fly Predators Ineffective?
Fly predators are ineffective if they cannot successfully finish their development. When you purchase your fly predators, they come as larvae inside parasitized fly pupae. They may need more time to develop and exit the puparium. Store them at room temperature until they begin to hatch from the host pupae. Do not leave them in direct sunlight or extreme heat.
For best results in the Spring, Fall, and Winter, keep your parasites at about 26°C. Temperatures below that slow the process. During the summer, warmer temperatures can speed up the hatching process. If you receive your fly predators and they have already hatched, release them around your property immediately.
Will Chickens Eat Fly Predators?
Yes, it’s common for chickens, ducks, and geese to feed on fly predators. Chickens love most insects and can sometimes eat live fly predators. However, most commonly, chickens inadvertently eat fly predators while foraging the ground for a host fly’s pupae.
For this reason, after you apply the parasitized pupae around the various hot spots on your property, you want to cover them with dirt, straw, or the sawdust or wood shavings they were shipped in. You also want to avoid depositing them in areas where they can get trampled by heavy animals like pigs, goats, horses, or cattle.
Do Fly Predators Bite?
No, fly predators like Muscidifurax raptor do not bite or sting humans or other animals. Their primary concern is seeking out suitable hosts for their offspring. Plus, adult predator flies are nocturnal so they are hardly noticeable when they are most active.
Final Thoughts
Nuisance flies on your property are not only annoying. They can also affect your animals by biting, infecting, and spreading diseases. You can control the population of nuisance flies on your farm or homestead with parasitic fly predators like Muscidifurax raptor.
Parasitoids like Muscidifurax raptor hunt for and infect fly pupae they find on your property. They kill the fly larvae inside and use the fly’s puparium to lay their own eggs. Once the parasitoid’s eggs hatch and the insect develops into an adult, it leaves the egg and reproduces, continuing the cycle, or goes off to parasitize a host.
Using fly predators to mitigate nuisance flies on your farm is super effective, but it should only be one piece of the puzzle. You should also integrate other preventive tactics like proper manure management, removing compost, fixing leaks, and keeping feed storage areas clean and dry to mitigate the development of nuisance flies on your farm.
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