For a growing industry in a rapidly changing environment, the presence of pests is an ongoing concern. Numerous species of flies can breed in litter and manure, come to maturity (some in as few as seven days; most in two weeks), and disperse up to a mile or more from their breeding place. Manure handling systems must be carefully managed to prevent these annoying creatures from spreading disease (always a serious problem) or becoming a public nuisance and a focus for bad feelings.
Identifying the Enemy
Moist litter is not only a threat to surface and groundwater; it is also an ideal breeding ground for flies. Caged layer operations are the most susceptible to this problem, followed by breeder farms and, occasionally, broiler farms. Wherever poultry houses are susceptible to flooding, or litter is stored outdoors, the potential exists for fly-control problems.
Several species, including house flies (Musca domestica), blowflies, and Fannia spp., are bothersome, but it is the common house fly that creates the greatest outrage and danger. It crawls over filth and food products, breeds in all kinds of organic matter (plant material, spilled grains, and animal wastes), and reproduces by the thousands.
A nuisance? Yes, but also a carrier of disease for animals and people.
Flies, which generally become active in the early spring (mid-March in many areas), have four stages of development: egg, larva, pupa, and adult. Most generations require about two weeks to develop. Females will produce 120 to 150 eggs in three or four days, and hatching occurs be- tween eight and 24 hours later. House flies can complete their entire life cycle in as few as seven days; therefore, many of the newly hatched 150 flies will also breed within a few days. Twenty to 30 generations in a fly season is not unusual. As many as 1,000 flies can develop in a single pound of suitable breeding material. The actual rate of development depends, however, on the temperatures and moisture levels in the breeding area.
Management of manure so that it is not conducive to fly breeding is the most effective means of control. Fresh poultry manure generally contains 60 to 80 percent moisture. Fly breeding in this material can be minimized by reducing the moisture content to 30 percent or less. This reduction also encourages the development of beneficial insects that can displace developing house- flies or serve as predators of fly eggs and larvae, or both. Dry manure management is practiced under two types of systems: (1) frequent manure removal (at least weekly), and (2) long-term, in-house storage of manure. Frequent manure removal systems to prevent fly breeding are based on weekly (or more often) removal, spreading, and drying of manure to break the fly breeding cycle. This system is effective if done regularly and thoroughly, but it requires adequate agricultural land where manure can be spread.
In-house storage of manure calls for drying the manure to about 30 percent or less moisture level and the capacity to maintain this level for up to a year. Where sufficient storage space is available, dry manure can be maintained for several years before being removed.
Once removed, land application is generally made. When poultry litter is applied, it should be spread thinly to promote drying. If fly larvae are in the litter, then incorporating it into the soil as quickly as possible will help break the fly development cycle.
Good housekeeping and management practices that keep manure and litter dry are a first line of defense against flies. A partial list of such practices includes the following:
- Water troughs or cups should be free of leaks, drips, and condensation. The water pressure should be properly adjusted (to prevent dripping) and an on/off cycle should be used (to control condensation).
- Adjust the floor/grade relationship if the water table is high or if outside water can penetrate the house.
- Provide abundant cross-ventilation and avoid excessively high temperatures.
- Prevent dysentery with antibiotics, if necessary, and avoid foods that have a known laxative effect.
- Avoid excessively high house temperatures that encourage abnormal water intake.
- Use absorbent litter materials.
- Consider combining deep pit manure storage with composting for layer operations.
Chemical Controls
Under certain conditions, insecticides may be used to control adult flies in barns and poultry houses. But these products should be reserved for critical times when the management system breaks down, because flies quickly develop resistance. Insecticide applications may be regulated in some states and should be handled carefully to minimize any harmful effects associated with toxic ingredients.
By increasing their focus on outcomes, rather than inputs, growers will find that they have many more tools than insecticides to help them control flies. Consider composting, for example. Undisturbed litter that is free of moisture will slowly begin to compost naturally, and it will support a large number of predators and parasites that feed on fly larvae. These predators include beetles, mites, and parasitic wasps. Scavenger insects help aerate the litter and make it less suitable for fly development. Take care, however, to leave the litter undisturbed; time is needed to encourage the buildup of the beneficial insects. Schedule complete cleanouts, therefore, in the off-fly seasons, and make only spot applications of insecticides in the meantime to reduce the potential for resistance to insecticides.
Integrated Pest Management
Among many reasons to include new waste management practices and beneficial insects in the battle against flies is the dawning recognition that flies are not going to be eradicated. Instead, an integrated and routine program to control them must be implemented and practiced throughout each year. Other reasons to integrate pest management measures involve changes in our understanding of and attitudes toward pesticides:
- The choice of effective pesticides that can be safely applied is limited;
- Flies develop resistance to even the most potent pesticides;
- Avoiding insecticide residues in animal tissues and other products is essential; and
- Pesticides are included in a general concern for the effects of agricultural chemicals on the environment.
Pesticides should be used, therefore, as part of an integrated system and with proper attention to practices that will minimize these concerns. Thus, consider insecticides as supplemental to good housekeeping and waste management, and use space spray with no residue to gain immediate control.
Use sprayers made especially to form aerosols that will remain in the air long enough to catch the adult fly and make the application early in the morning before the flies fly up to ceilings and support posts. Using portable equipment may help the applicator reach some difficult areas around the house.
Fly baits in wet or dry form can also be used as supplements to other methods. Liquid baits must be prepared by the applicator and brushed or sprayed on fly resting areas. Larvicides can be applied to manure below the cages and around waterers, but treating manure regularly (and throughout the facility) is not recommended. Such a practice is costly, the flies quickly develop resistance, and the treatment will also kill the beneficial insects.
Some growers may want to investigate other practices; for example, feed-through larvicides or the commercially available parasitic wasps or soldier flies, which reduce the volume of waste and crowd out houseflies.
Sticky fly papers and spot cards can be used to monitor the presence of flies. Spot cards are plain white cards stapled so that each side is available for the flies to rest on. The resting flies leave brown regurgitation and fecal spots on the cards, which are then retrieved and the spots counted. Chemical treatments are advised if the grower finds 50 spots per card per week. The cards also provide a handy record of conditions — and indicate the grower’s use of controls — should such a record be needed.
Some type of regular “scouting” or inspection schedule should be used throughout the year to determine where and when the fly population is developing, and therefore where and when to use cultural practices or pesticides. It can also help the grower determine the effectiveness of the control program overall.
References
Axtell, R.C. 1985. Arthropod Pests of Poultry. Pages 269-295 in R.E. Williams et al. eds. Livestock Entomology. John Wiley and Sons, New York.
Collison, C.H. 1996. Manure Management Strategies to Control Flies. In Manure Management for Environmental Protection. Reprinted as Fact Sheet. Pennsylvania Cooperative Extension, Pennsylvania State University, Lancaster.
Nolan, M.P. Jr. 1988. Control External Parasites and House Flies Around Poultry Operations. Bulletin 723. Cooperative Extension Service. College of Agriculture, University of Georgia, Athens.
Strother, G.R. 1990. Fly Control in Poultry Operations. DTP Circular 12/90-015. Cooperative Extension Service, Auburn University, Auburn, AL.
Williams, R.E. 1990. Fly Control in Poultry Houses. E-3. Cooperative Extension Service, Purdue University, West Lafayette, IN.
———. 1997. Fly, Beetle Control Continues to Concern Poultry Producers. Poultry Times, June 2, pp. 1, 5, 19.