A parasitic wasp kills a stable or house fly by stabbing a fly pupa and laying an egg inside the case, after which a developing wasp larva eventually eats the pupa.

Need a successful method to control stable flies and house flies in your cattle feedlot, dairy or equine center? Give this killer fly recipe a try:

  • Eight parts sanitation
  • Two parts naturally occurring enemies
  • Five parts introduced parasitic wasps
  • One part fly baits, traps and oral larvacides
  • Three parts insecticides
  • And a heaping dose of knowledge and common sense

Mix thoroughly, and this recipe should allow you to keep stable and house flies to manageable levels while keeping peace with your cattle, horses, employees, neighbors and inspectors.

“Several years ago, some companies selling parasitic wasps would cringe if the word ‘pesticide’ was even mentioned,” said nationally recognized veterinary entomologist Bill Clymer, Ph.D., president of Agricultural Training and Technology Inc., in Amarillo, Texas. “Today, those people, like the chemical industry, realize that it takes an integrated pest management (IPM) program to effectively reduce and control nuisance flies, and using both parasitic wasps and insecticides are important parts of this.”

Two people on both sides of the fence agree with Clymer.

“I would say that the major players in the biocontrol industry believe in an integrated approach, and using both parasitic wasps and insecticides to control flies in feedlots, dairies and equine facilities is part of that approach,” said Sinthya Penn, president of Redding, Calif.-based Beneficial Insectary, which sells a variety of natural enemies to help regulate pest populations, among them tiny, gnat-sized wasps to control flies.

Doug Ross, senior technical services entomologist for Bayer, agreed, stating, “Whenever we talk with producers, we tell them that insecticides are just one of several tools they need to achieve fly-control objectives. An integrated approach is truly needed, and though every tool in an IPM program is important and will help — whether a parasitic wasp, an insecticide or something else — no single one is a magic bullet.”

Ross and Penn concurred with Clymer that arming yourself with knowledge is critical, everything from being able to properly identify pests to developing and carrying out a sound IPM program. They also support Clymer’s belief that “sanitation, sanitation and sanitation” should top the plan.

“If you do any one of those three things, you can significantly reduce your fly control issue,” Clymer said.

More and more producers are taking steps to improve sanitation, and they also are realizing the importance of parasitic wasps.

“The biocontrol industry, as a whole, has grown tremendously in recent years,” Penn said. “When I became president of Beneficial Insectary in 1986, we were probably shipping one million fly parasites per day during the fly season. That number has grown to 100 million parasites per day, which are being trucked to feedlots, dairies, equine facilities and poultry operations across the country. Customers want results, and they are getting results.”

But are parasitic wasps economical?

“If they were not, we would not be selling them to companies that provide fly control with chemicals as part of their management program,” Penn said.

Ross, whose company is in the insecticide business, offered the following: “If you are a cattle feeder or dairy operator, I hope that you’re not on a regular spraying schedule because you shouldn’t use insecticides unless there is a specific need. If you’re releasing wasps on a regular basis and you come to a point where you need to spray to help get your fly numbers down to a manageable level, that’s the time to use an insecticide.”

Penn added, with emphasis: “Consider chemicals your big gun; save that gun [for] when you need it the most.”

Consider, then, that parasitoids are your arsenal of small guns. During the fly season, Penn said, weekly releases of about 300 to 500 wasps per animal are ideal. These will augment populations of natural enemies, including certain species of wasps, mites and beetles.

Insecticide placement and timing can be coordinated around fly parasite releases so that adult wasps are not harmed.

“If a person wants to learn more about biocontrol and how to successfully work it into an IPM program, contact more than one company before making any decisions,” Penn advised.

A good initial source for information about biocontrol, along with a list of producers and distributors, is the Association of Natural Biocontrol Producers website (http://www.anbp.org/).

“Knowledge is power, and please understand that the entire parasitic wasp industry has grown out of need,” Penn said. “Beneficial insects saved the California citrus industry twice, and they are now a very important part of insecticide resistance management, and it’s hard to put a price on that.”


New fly management tool available

Starting in 2016, cattle feedlot and dairy operators have another tool to manage nuisance flies and mosquitoes.

DeltaGard is a new insecticide product from Bayer for wide-area control of house flies, stable flies and mosquitoes. It contains a pyrethroid called deltamethrin.

The product is applied with hand-held, backpack, portable and truck-mounted ultra-low volume sprayers and portable and vehicle-mounted mist blowers, said Doug Ross, senior technical services entomologist for Bayer.

Producers can rotate DeltaGard with other classes of insecticides including organophosphates for adult fly control.

“Since insecticide resistance is an issue, do everything else you can to get fly numbers down before using them, and then rotate between classes,” Ross suggested.

Bayer technical services veterinarian Larry Hawkins, DVM, added: “I am excited about DeltaGard because I believe it gives feedlot and dairy operators a good tool during stable fly outbreaks. Once you kill off a big population of the flies, you use your other management tools, including sanitation and parasitic wasps, to keep flies at a manageable level.”

Always read and follow label instructions.


(Photo by the late Mike Rose, courtesy Beneficial Insectary)