Odor and Nutrient Management Newsletter

Summer 2001

Fly control starts with manure management

by Ken Holscher, Department of Entomology

House flies are the predominant flies found in and around livestock and poultry facilities. Although house flies can develop in just about any type of decaying organic material, the large accumulations of manure generated in these facilities has the potential to produce significant fly populations. Thus, manure management is of critical importance and should form the basis of an effective house fly control program.

During warm weather house flies can complete their life cycle in as few as 10 to 14 days. Removing manure that accumulates in livestock and poultry facilities on a weekly basis and spreading this manure thinly on fields to dry could provide effective house fly control. However, the lack of available land on which to spread the manure, increased labor requirements, and other factors seriously limit the usefulness of this approach and have necessitated the development of facilities designed for long-term manure storage.

Although house flies can develop in any type of manure, they cannot develop in manure that is too wet or too dry. Therefore, confinement facilities that incorporate long-term manure storage are usually designed with either a dry manure system or a liquid manure system. For example, most caged layer facilities incorporate a dry manure system where birds are housed in the top floor of the unit and the manure accumulates on the bottom floor. The key is to promote rapid and thorough drying of the manure and to eliminate or minimize moisture buildup. To do so requires effective ventilation, inspection and repair of leaking watering systems, evaluation of feed and water salinity, proper grading of outside areas to promote adequate runoff of rainwater, and identification of other factors that may contribute to excessive moisture problems. If additional moisture problems are avoided the manure can cone and effectively dry so that fly reproduction is substantially reduced. It also promotes the establishment of naturally occurring predators and parasites, which further aid in reducing fly numbers.

Rather than a dry system, many swine facilities incorporate a system where liquefied manure is stored in a pit. These facilities typically experience excellent fly control for the first year or two of operation. However, after that time a crust may form over the manure, which provides an excellent breeding source for house flies. Unfortunately, removing or breaking up this crust or treating the crust with an insecticide is extremely difficult.

Manure management is also important in open livestock facilities such as beef feedlots. In these facilities the lots should be stocked to maximum capacity to facilitate trampling and subsequent drying of manure. Mounds should be constructed or maintained to dry rapidly and allow adequate and thorough runoff of rainwater. Low areas within lots should be filled or graded to prevent water accumulation. Watering tanks should be adequately maintained to prevent water from collecting around the base. Manure that accumulates underneath fences or in similar adjacent areas should be removed. Other potential fly breeding materials such as spilled feed and wet bedding also should be removed on a frequent basis.

Although manure management forms the basis for an effective fly control program, supplemental measures may be needed. Chemical control options include space sprays, residual wall sprays, larvicide sprays, baits, and feed additives. Space sprays provide a quick knockdown of adult flies but provide no residual control and may need to be applied on a frequent basis. Residual wall sprays applied to areas where flies rest can provide some level of control for several weeks. Sprays are also available for application to manure to control fly larvae but are not generally effective and are only recommended as a spot-treatment. Baits can aid in the reduction of house flies but should only be used in limited areas to avoid unnecessary exposure to nontarget animals. Feed additives are available for use in some production systems and can aid in control if fed before fly numbers have reached high levels. Biological control options include the release of commercially available parasitic wasps. These wasps can help reduce fly numbers if they are introduced early in the spring before fly populations have had a chance to build up. Although these wasps can be released into all types of livestock and poultry facilities, they seem to work best in caged layer facilities as opposed to swine facilities or open feedlots.

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Iowa Manure Matters: Odor and Nutrient Management is published by Iowa State University Extension, with funding support from the USDA Natural Resource Conservation Service through Cooperative Agreement No. 74-6114-8-22. To subscribe or change the address of a current subscription, write to Angela Rieck-Hinz, 2104 Agronomy Hall, Iowa State University, Ames, Iowa, 50011-1010 or call 515-294-9590, fax 515-294-9985 or email: amrieck@iastate.edu. Please indicate you are inquiring about the Odor and Nutrient Management Newsletter. The newsletter's coordinators are Angela Rieck-Hinz, extension program specialist, Department of Agronomy, Wendy Powers, environmental extension specialist, Department of Animal Science, and Robert Burns, Department of Agricultural and Biosystems Engineering; the editor is Jean McGuire, the subscription manager is Rachel Klein, the production designer is Beth Kroeschell, and the web page designer is Liisa Jarvinen.

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