MANAGEMENT OF FILTH FLIES

WITH PARASITIC WASPS

Rincon-Vitova Insectaries is a pioneer in growing beneficial insects to control flies in animal manure accumulations and other filth fly breeding sites. The species of flies that inhabit accumulations of manure are attacked by over 200 kinds of predaceous and parasitic species of insects, spiders and mites.

Combinations of these beneficial insects are attracted to manure, destroying all life stages. Beetles and mites devour fly eggs and larva. The adult fly stage is partially controlled by natural disease. The pupa (or cocoon stage) also has one of the most important natural enemies of flies: small parasitic wasps. Parasitic wasps find fly pupae with biological radar in manure and other fly breeding sites.

Our insectary mass-produces several species of tiny wasps in the genera Muscidifurax and Spalangia that attack fly pupae. Because each species in our mixture is adapted to different climates, we increase the proportion of Spalangia to Muscidifurax as seasonal temperatures rise. Hundreds of our satisfied customers from more than 20 years of service find our product helps reduce or eliminate the use of pesticides.

HOW FLY PARASITES WORK

Parasitic wasps lay their eggs inside fly pupae and prevent the flies from emerging as adults. Immature stages of the parasites feed on the juices of the fly pupa. Adult parasites also prevent fly emergence by drawing fluid from fly pupae during host feeding. These parasites are very effective against the housefly, biting stable flies, garbage flies, and the lesser housefly, which comprise 95% of the flies in manure accumulations. These parasites will also attack blow flies and bottle flies breeding in and around garbage dumpsters. The parasitic wasps only attack flies and will not bite, sting, swarm or bother anything else. They are nocturnal and are rarely seen during the day. Fly parasites operate to a depth of 8 inches in manure, homing in with their biological radar on fly larvae that are about to pupate.

Fly and Parasite Life Cycles

(at approximatemly 80º F, 27º C)

Fly parasites complete a generation every 3 weeks, (from parasitism of the fly pupa to emergence of the adult) thus at least three weekly releases are recommended to yield a steady production of adult parasites. With weekly releases, a noticeable reduction in flies can be expected in 4 to 6 weeks as the parasite population increases. They will eventually find and kill most of the flies at your location. However, because adult flies still can be migrating in, other control strategies such as trapping must be used. Biological control will work better for you if you and your neighbors use multiple strategies for fly control.

STEPS TO THE SUCCESSFUL

MANAGEMENT OF FLIES

1) REDUCE THE NUMBER OF ADULT FLIES

Flies have a much higher reproductive advantage than parasites; a single fly can lay up to 800 eggs a day, whereas a single parasite will attack less than 30 fly pupae a day. Flies also have an advantage of a shorter life cycle than parasites; 8 days in hot weather up to 14 days in moderate weather compared to 18 to 28 days for parasites. Adult flies are able to travel greater distances faster than parasites. The shorter life cycle also allows flies to become resistant to insecticides faster than parasites. By keeping the number of adult flies down, parasites will be better able to keep pace with the number of fly pupae. Because the fly has the edge, the population of fly parasites needs continuous reinforcement through augmentative releases of insectary-grown parasites in order to maintain a high level of fly control.

Fly parasite emerging from fly pupae

USE FLY TRAPS

Trapping adult flies with baits is recommended to accompany fly parasite releases. Some chemicals or nonpoisonous materials are useful when they are formulated into sugar baits. Bait traps can be economically and safely used to remove large numbers of adult flies without interfering with biological controls. Baited jug traps are easy to make, very effective and keep the bait out of way of children and pets. Reducing the adult fly population early in the fly season (usually beginning after the first frost-free day of the year) give the beneficial population the time needed to increase to larger numbers in the manure and will result in fewer fly problems for the rest of the summer. Sources for purchasing and directions for making your own traps are available.

In humid areas and in wet manure accumulations, especially where manure is washed into pits, it takes both releases of parasites and bait stations to give excellent fly management. Set up at least one bait trap inside each barn or shady area where you see high numbers of adult (as indicated by fly specking) when you start releasing parasites. Trapping should continue with parasite releases until adult flies are gone.

Sagebrush Trap S3

2) REDUCE FLY BREEDING SITES

Manure management

Good sanitation practices that eliminate conditions favorable to fly breeding are critical to limit fly problems. Frequent manure removal reduces the breeding sites. Keep areas around watering and feed troughs clean and dry. Maintain ventilation to keep manure dry and eliminate wet areas wherever possible.

Large amounts of manure can be managed in a pond or storage where non-aerobic digestion is accomplished or by aerobic composting systems. Unprocessed manure can be piled and covered. This reduces the surface and heat builds up to reduce fly breeding. Dry manure will not breed flies. The interface between wet and dry manure that has a moisture content of 50 to 80 percent is where fly breeding occurs. This is also where the fly parasites work best

ESTIMATING NUMBERS OF PARASITES

Parasites are sent as approximately 10,000 parasitized pupae at approximately 75% parasitism to yield one standard colony (minimum 20,000 adult parasites). Factors affecting recommended numbers of parasites include numbers of flies, amount of manure or other organic matter, moisture content, humidity, temperature, existing beneficial controls, chemical usage, use of bait traps and incoming migrations.

Below are some suggested release rates based on the number of animals. Other factors to consider are temperature, moisture (rainfall) and the number of potential fly breeding sites. Fewer parasites may be needed during cool dry weather especially if other control strategies such as frequent manure removal and trapping adult flies are used.

Schedules and numbers of units used in some typical seasonal programs: (1 unit = 1 FP10)

Area	Rate	Frequency	Amount suggested
Stables	100 parasites/horse	every 2-4 weeks	1-4 units/month for up to 30 horses
Feedlots	250 parasites/head	every 1-2 weeks	7-10 units/week for 1,000 head
Dairies	200 parasites/cow, 1,000/calf	weekly	5-7 units/week for 100 cows
Poultry breeders	6 parasites/bird	weekly	5 units/week for 10,000 breeders
Poultry layers	4 parasites/bird	weekly	1 unit/week for 10,000 layers
Compost	500-1,500 parasites/cu. yard	monthly	5-15 units/month for 100 cubic yards

To develop a basic release program, increase or decrease suggested release rates based on these factors:

Factor	Increase	Decrease
number of flies	high	low
manure or organic matter	a lot	little
manure moisture content	wet	dry
control measures established	no existing program	good program
rain	regularly	little
humidity	damp	dry
drainage	could be better	good
animal watering equipment	leaky	no leaks
temperature	hot	cool
existing biocontrols (i.e. beetles, mites & fungi)	few	many
bait traps	don’t use	use
flies migrating in	yes	no
flies hauled in (i.e. to composting sites)	yes	no
comfort level with flies	low	higher
neighbor’s comfort level with flies	low	higher
budget for control	good	low
health concerns	yes	no

TIMING RELEASES

It is easier to prevent a build-up of flies than to get rid of them. A few flies always survive the cold and drying conditions of winter in the pupa stage. Parasite releases should be made early each spring at the first sign of emerging or immigrating adults to minimize the numbers of adult flies laying eggs. Very early releases can be smaller in number, increasing in quantity at the first signs of active breeding. Once established fewer parasites are needed to maintain an effective number. A few may overwinter outdoors, but yearly augmentation is necessary.

PUTTING PARASITES OUT

These parasitic wasps arrive developing inside the fly pupa. When fully grown, they cut a hole in the pupa case and exit as adults searching for more fly larvae, seeking to lay their eggs where the flies pupate. The date on the bag is an estimated emergence date.

Sprinkle a small handful or spoonful of the parasitized fly pupae in wood shavings either on manure or in furrows and lightly cover to protect from birds. The widest possible dispersal around fly breeding areas is best.

Locating the fly breeding sites is critical to using the fly parasite effectively for fly control. Fly parasites should be released around any area where maggots are seen. Places to look for these sites are in and around coops, kennels, barns, stables, and stalls, with special attention to maternity, hospital and calf pens on dairies and fence lines and feedbunks on feedlots, and wherever straw bedding is provided for animals. Place also around corral posts, fence lines, paddock areas, and other dropping sites, at the edges of manure piles, pits or carts, and wherever manure accumulates. Other fly-breeding areas are near (but never directly in) water sources and decomposing matter in garbage cans and septic tanks.

HANDLING OF PARASITES

Fly parasites must not be left in direct sunlight or hot areas. If ordered fresh, they may be held at 70°- 80° F, increasing to 85° F for more rapid emergence; otherwise, they are emerging and ready to release within a day or two. Cold storage shortens life and may harm reproduction. Avoid chemical sprays within 48 hours of release. Rincon-Vitova offers screen mesh release stations for hanging in barns where floors are washed regularly or predation by rodents is likely.

EVALUATING PARASITE EFFECTIVENESS

1) ASSESS PARASITISM OF FLY PUPAE

To assess the parasitism of fly pupae in manure, fly pupae can be separated from the manure by flotation in water. Agitation will float the pupae to the surface. Pupae that are old enough to have been exposed to parasitic wasps change from reddish to dark brown. Up to ten percent of these will not develop into flies. Those yielding flies have the end of the pupal case broken off. Neatly cut escape holes are evidence of parasitism. Check 100 dark brown pupae in a week for parasitism and dead intact pupae to get parasitism rate and possible parasite-induced mortality rate.

2) MONITOR NUMBER OF ADULT FLIES

Since adult flies are the pest, a reduction in the number of adult flies is the best measure of a successful integrated fly control program. Control decisions should be based on a standardized method of quantifying fly numbers. Baited jug traps and index cards offer two standardized methods.

Counting the number of flies caught in baited jug traps or on fly tapes is an excellent way to monitor changes in fly populations. These traps are easily made by hanging a gallon milk jug that has four 2-2½ inch holes in the top half of the with a wire. One ounce of bait should be placed in the bottom of each

trap. Baits containing the fly pheromone muscalure (Muscamone^®,Z-9-tricosene) are the most effective at attracting flies. These traps should be hung about 1 foot below beams near areas where flies are often seen resting or where fly specks are concentrated.

The trap should be emptied weekly and the number of flies caught counted. In general, fly activity is considered high if more than 250 flies are caught in a trap in a week.

fly parasite wasp

actual size is approximately 1/10 inch

Weekly placement of 3 X 5” plain index cards near fly resting areas as indicated by fly specking provide an inexpensive method for monitoring fly populations as well as a historical record of fly activity. These cards should be fastened flush to a surface where fly specks are concentrated. Cards should be placed in the same position at each renewal. In general, fly activity is considered high if each card on average has more than 50-100 spots in a week.

INTEGRATING CHEMICAL CONTROLS

Biological control works because of the entire complex of insectary-grown and naturally-occurring predators and parasites of all stages of flies. All natural enemies of flies are susceptible to pesticides, particularly when directed at manure. Reduce adult populations with poison baits. Spray only adult fly resting areas with long residual pesticides. This way you keep biological control working for you and reduce the need for insecticides.