Question of the Week
Answer: Flies of concern may include members of the family Muscidae that includes house flies, stable flies, horn flies and face flies. The habits of these are summarized in the chart below. Although certain flies favor barns or confinement settings and others are found more in pasture, some eat filth, others such blood and others feed on secretions, all flies reproduce rapidly and can cause trouble that it is worth the effort to prevent. The life cycle is complete metamorphosis: depending on conditions, fly eggs may hatch in a day. Fly larvae (maggots) pass through three larval instars and a pre-pupal stage within about a week, and adult flies begin laying eggs within a couple days.
These flies are pests because at a minimum they cause animals discomfort, and are estimated to reduce weight gain by 25% (18) and decrease milk production up to 15-30% (15) or even 40-60% (18). Flies, can transmit all manner of diseases (2) including bacterial diseases such as cholera and anthrax, and eggs of parasitic worms (10). The threshold that indicates a high level of activity for stable flies is just 10 flies per animal. Other flies not discussed here include external parasites that live part of their breeding cycle on/in animals.
The most economic and practical method of controlling flies is to reduce their breeding. The most effective way of reducing fly breeding is to eliminate areas that provide fly habitat where larvae feed and develop in wet or moist manure and other decaying organic matter. Observe the area where flies are a problem and figure out where the flies are breeding. Different flies have slightly different life cycles for breeding as well as different habits for being pests on animals. The latter will help you identify what fly or flies are present, and more effectively address the breeding problem at its source. All the other approaches listed below are complimentary, and will be most effective when used together with good sanitation.
A comparison of fly pests.
Fly species: common, scientific
Life cycle; eggs laid by each female
Location on farm and on animals
Form of feeding and habits; animal reaction
7-21 days, egg to adult (13);
150-200 (2) up to 500 (10) eggs per fly
Moist organic materials: fresh manure, bedding,
Feed on filth
12-21 days eggs to adult
200-400(2) or 500 (10) eggs/fly
Decomposing plant matter such as wet straw and grass
legs and bellies
Pierce skin, suck blood; Animals stamp their feet. >10 flies/ animal=high activity.
As little as10-12 days egg to adult
Lays 375-400 eggs (10)
Fresh manure (2-3 days old)
shoulders, backs, sides, midline.
Feed on blood.
Flies fly into manure as animal deficates
Moist fresh manure.
Live in cooler and coastal areas, not in hot, dry climates.
Pasture -- do not enter barns;
Face, eyes muzzle.
Feed on secretions around eyes.
Can transmit pinkeye (13).
Animals gather with heads together.
Sources (1, 2, 10, 13, 15) and many others)
Reduce fly breeding areas around barns and buildings
- Remove or move manure, bedding, waste and other sources of food for fly larvae. For most flies, the breeding cycle may range from 10 to 60 days (shorter in warm conditions and longer when the weather is cool). Move fresh manure, bedding and spilled feed and from barn areas every 2-3 days (10) if possible to break this breeding cycle.
- Keep animal barns and yards dry. Repair any leaky pipes promptly. Address any other sources of water that may help create areas that are ideal places for flies to lay eggs and their larvae (maggots) to develop. Clean drainage ditches. Cover silage.
- Keep drinking water fresh and clean. Dump water where it will be used by plants or dry quickly. Avoid creating places that stay soggy.
Keep flies out
- Ventilate barns to maintain good air circulation.
- Put up physical barriers such as screening on windows, and keep doors closed whenever it is practical.
Reduce Fly Breeding areas in Pasture
- Manage pastures using strategies such as rotational grazing to interrupt pest life cycles. Fly eggs, maggots, pupae and adults all die after a while.
- Disperse, break up and dry out manure paddies by dragging a harrowing. This is especially important early in the season before populations multiply.
- Encourage dung beetles by avoiding pesticides such as synthetic parasiticides (Ivermectin) or using them judiciously. Dung beetles break apart and incorporate fresh manure into the soil, eliminating breeding areas and thus reducing horn fly populations.
- Incorporate pastured poultry into your garden, pasture or farming system to eat fly larvae and help keep populations down. Both domesticated and wild birds in animal pastures, including chickens, ducks, geese, guinea hens, and cattle egrets will pick through paddies and eat fly eggs and larvae. Chickens are even adept at catching adult flies. Eggs or other poultry products may be an enterprise for farm income diversity.
- Compost organic materials using aerobic methods. A hot compost pile (where heat is generated by decomposition) will kill fly larvae, and presents an inhospitable place for adult flies to lay their eggs.
Fly traps: many possible designs and variations are allowed for use in organic production.
- Indoor traps include sticky traps or fly tape. Place these near beams and walls so they do not catch bats, and away from any barn swallow nests. Pheromone traps may be more effective against certain species of flies.
- Outdoors, an inverted cone traps consist of a cone with a hole in the top that opens into a space enclosed with screening from which flies cannot escape. Smelly bait under the cone will attract flies so they fly up through the hole in the top of the cone into the enclosed space where they die. These traps should be placed in full sunlight, sheltered from strong winds, and within 6 feet of active breeding areas, such as at the ends of barns manure piles or calf hutches.
- Walk-through traps can help reduce flies—especially horn flies--on larger animals. Strips of canvas dislodge flies from animals' backs and sides. Attracted to the light, they fly up and become trapped between two layers of screened mesh. Plans are available from various sources including ATTRA. Please note that some plans for walk-through fly traps recommend the use of treated lumber. Organic producers must find alternatives to using this prohibited material. Please see ATTRA's publication entitled Alternatives to Treated Lumber. Walk-though traps can be placed anywhere where animals must pass, such as the entrance to the milking barn, and to sources of water. While cattle may need to be trained to walk through such an unfamiliar space at first, they may later walk through to achieve its benefits even when it is freestanding in a pasture.
- Use bug zappers to kill adult flies. These are most effective when the bulbs are replaced frequently enough to keep the ultraviolet wavelength attractive to insects. Keep records of their date of installation; a light that appears all right to the human eye may not maintain that proper wavelength.
- Recognize and encourage predators: Hister beetles are small, shiny black beetles that eat fly eggs—one beetle can eat as many as 24 eggs per day. Predatory mites also eat fly eggs and small maggots (15).
- Release fly parasites such as parasitic wasps. The Cornell website on biological notes the use of the parasitic wasp Muscidifurax raptor for control of the housefly Musca domestica and stable fly Stomoxy calcitrans, as well as different types of bacteria, fungi, and nematodes for flies. The wasp Muscidifurax raptor may be most effective in hot and humid conditions. Other wasps or mixtures of wasps may be more effective in other areas. Consult with an insectary or supplier of beneficial insects about which parasitic wasps are most appropriate for your species of fly, type of livestock and region. A supplier should also be able to provide recommendations on the best conditions, locations, frequencies, and numbers of releases. Remember to protect these beneficial insects from getting too hot, cold, wet or dry. Releases may be most effective when done weekly, and will probably need to be done every year because their numbers decline in winter.
- Provide habitat for bats, and birds such as purple martins (in the parts of the country where they live). Several species of bats and birds will inhabit appropriately constructed and well-placed nest boxes or other types of enhanced or artificial housing, and help by eating flies.
- Some pesticides are allowed for use in organic production a complement if other methods are unsuccessful or insufficient. Such materials should be used to complement, not substitute for other methods as listed above. Before you use any organic or biological pesticide, you must include it in your organic system plan that is approved by your organic certifier. Botanical and allowed synthetic pesticides may be found in various product formulations at feed stores and farm coops. Organic or natural materials often have inert ingredients or synthetic carriers that are not allowed. Botanical pesticides also need to be labeled for use on cattle or other animals where you intend to use them. All synthetic pesticides, including insecticidal ear tags, are prohibited in organic production. It is good to check with your veterinarian to see if she or he has any experience in administering organic pesticides in animal production.
1) Fanatico, A. 1996. Alternative Fly Control. Butte, MT: National Center for Appropriate Technology. (out of print)
2) Macey, Anne, Ed. Canadian Organic Growers, Inc. 2000. Organic Livestock Handbook, Fly and Rodent Control chapter, pages 50-63.
3) University of Nebraska at Lincoln, Dairy Cattle Insect Management: Fly Control and Cattle Lice sections. http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=495
4) Biological Control: A Guide to Natural Enemies of North America
Note: This site provides photographs and descriptions of over 100 biological control (or biocontrol) agents of insect, disease, and weed pests in North America. It is also a tutorial on the concept and practice of biological control and integrated pest management (IPM). Excellent photos and lifecycle descriptions.
5) Organic Valley Co-op. Controlling external parasites on the organic farm. http://Organicvalley.coop/pdf/pools/controlling_parasites.pdf
6) Dr. H.J. Karreman, DMV. January 2002 Newsletter. Penn Dutch Cow Care
7) Dr. Hubert J. Karreman, VMD. Treating Dairy Cows Naturally.
8) Paul Dettloff, DVM. Alternative Treatments for Ruminant Animals
9) Little, V.A. 1963. General and Applies Entomology. Harper and Row Publishers.
10) Organic Materials Review Institute (OMRI). June 2004. OMRI Generic Materials List, under Livestock Production Materials: enzymes.
11) Those Pesky Lice! By Cheryl K. Smith. Dairy Goat Journal May/June 2005
12) UC IPM Online. April 2004. Pests of Homes, Structures, People and Pets: Flies
13) Integrated Pest Management for Fly Control in Maine Dairy Barns. University of Maine Cooperative Extension Bulletin #5002.
14) Integrated Management of Flies in and around Dairy and Livestock Barns, DAIRY MANAGEMENT Pest Management Fact Sheet, 6/1994.
15) Make Your Own Fly Trap
Horse Talk New Mexico Horse Directory
16) David Shetlar, PhD. The Ohio State University, photos of Old Fly Traps.
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