Using Fly Parasites



Fly Parasites Prevent Fly Emergence in Dairy Farms

Fly parasites are natural inhabitants of cattle manure. However, their numbers are reduced to zero with manure cleanouts or after the use of strong pesticides. Without help, fly parasite numbers rebuild slowly. The major fly outbreaks that occur after cleanouts in poultry barns demonstrate the massive effect that natural enemies normally exert on fly populations.

Use of Fly Parasites:

Fly parasites prevent adult flies from hatching. These tiny beneficial insects kill fly pupae and then use the killed pupae as “nurseries” to grow new parasites. Fly parasites are tiny insects in the wasp family that live only to search out, kill, and lay eggs in fly pupae. They move about unnoticed because of their small size.


  • No Side Effects
  • Long-term Fly Control
  • Natural, Organic
  • Reduces Chemical Use
Pest Management

The illustration shows the stages of the fly life cycle. The fly adult, fly eggs and maggots are light grey in the background. The fly pupae are black and each has a fly parasite on it. The fly parasite to the left is a mature adult female that is preparing to sting and kill the pupa. It may also lay an egg inside the pupa that will mature into a new fly parasite. The fly parasite on the right is a new adult that has just chewed its way out of the host pupa.

Quality Assured: IPM Laboratories Fly Parasites come in units of 10,000 host pupae called colonies. Host pupae are inspected prior to shipment to assure that they carry fly parasites. Some pupae that have been killed by fly parasite attack do not carry new fly parasites. These empty pupae are not counted as host pupae.

FLY PARASITES SPECIES MIX: IPM Laboratories varies the mixture of species with the time of year: Muscidifurax raptor for the cold winter months. During the warmer seasons, we add Muscidifurax raptorellus. M. raptorellus produces multiple offspring per host pupa. M. raptor produces a single offspring in each host pupa. Nasonia vitripennis, a commonly available fly parasite, is not recommended for dairies since it has not been recovered from dairy barns.

Program Planning

Plan your fly control program in the spring. Call us and set up an IPM Laboratories Fly Parasite introduction program to kill fly pupae. Introduce fly parasites weekly or biweekly throughout the fly season, approximately May 15 through October 1 in the Northeastern United States.

Strategy for Fly Control in Dairies

Tipping the balance to favor the natural enemies and reduce the fly population requires an integrated approach that includes weekly removal of manure and other fly breeding sites, use of fly bait and sticky traps, release of parasitic wasps, and avoidance of residual insecticides. Residual sprays will continue to kill fly parasites for several weeks after they have stopped killing flies.

Release Parasitic Wasps in Fly Breeding Areas
Release parasitic wasps in fly breeding areas. A fly breeding area is usually moist organic matter which attracts flies to lay eggs and then supports the growth and maturation of fly maggots. Favorite breeding areas for flies include calf hutches, wet spilled feed, and moist manure and bedding (particularly straw). Under optimum conditions, with no natural enemies, 2 square feet of moist organic material can generate 10,000 flies in two weeks. Release fly parasites in the drier areas directly adjacent to breeding areas to kill the fly pupae before they turn into adult flies. Application rates are listed on the chart below. Scatter the package contents next to the fly breeding sites, or in nearby corners where they
will not be crushed, buried, or disturbed for several days.

Common Fly Parasite Release Rates
Site No. Host Pupae Unit
Calf Hutches 500-1000 per hutch
Bedded Pack 250 per animal
Cleaned Areas 1 5000-10,000 per barn or site
Wet Edges 2 25-100 per sq. foot

1 see text under Manure Management
2 see text under Other Breeding Sites

Equivalencies (volumetric, liquid measure):

Number of host pupae How to measure
500 1/20 colony 3 Tablespoons
1000 1/10 colony 3 ounce cup, or 6 Tablespoons
2500 ¼ colony 1 cup
5000 ½ colony 2 cups
10,000 1 colony 4 cups