POULTRYAND
LIVESTOCK
POULTRY
The information and recommendations in this newsletter are applicable to
North Carolina and may not apply in other areas.
Fly management on a hog farm is largely a matter of good sanitation. Flies are attracted to manure and other decomposing organic matter, and are not a serious problem where waste is handled properly. Modern hog facilities are designed to dispose of the manure and urine generated by a large number of animals kept in confinement. The proper maintenance and operation of these waste handling systems reduces the accumulation of material suitable for fly breeding.
The important phrase to remember in this discussion is, . . . suitable for fly breeding. The odors commonly associated with any type of animal facility (e.g., confinement buildings, corrals, kennels, stockyards, etc.) attract a wide variety of fly species. These can properly be thought of as the background population of flies attracted to potential breeding sites. This potential is always present with animal production, but it's wrong to assume that the surrounding area will be overrun with flies simply because a hog farm or other animal facility is nearby. A little understanding of what makes suitable fly-breeding habitat, fly movement and fly behavior will help the hog farm manager minimize the likelihood of raising more than hogs at his or her facility.
Filth flies (mainly house flies and related species) have specific requirements for successful reproduction. There must be suitable material (manure or carrion in this case) for them to lay eggs, and for the maggots that hatch from these eggs to feed. There must also be suitable sites for the fly maggots to pupate and complete their development to adult flies. On both counts, the design and operation of swine waste handling systems do not provide opportunity for successful fly reproduction. Manure and other wastes are flushed regularly into a lagoon where they are unavailable for fly breeding. Even where house fly maggots able to survive in the lagoon, adequately dry locations suitable for successful pupation may be limited. Fly breeding does occur on a modern hog farms of course, but it is minimal. In general, there is less suitable fly breeding habitat available in a properly managed hog building than there is in a horse barn half its size.
What potential there is for fly breeding on a hog farm can still be reduced, however. Accumulations of wet feed and wastes are the primary culprits. Clean up feed spills quickly, and periodically move feeders to clean out the material that collects beneath them. Solid wastes that may collect along flush gutters should also be removed every few days. Be sure to check any areas along the waste stream where solids may become trapped. Solids may also collect near outlets into lagoons. These accumulations should be broken up on a regular basis. Similarly, inspect the lagoon edge for areas where solids may have built up. Heavy crusting leads to conditions that favor house flies where the manure is just dry enough for them to breed. Control weeds along lagoon banks (especially near the water line) to eliminate snags that may trap solids where flies can breed. Heavy weed growth along the lagoon's waterline also provides cover and breeding habitat for mosquitoes. Inspect pits to be certain that no large, heavily-crusted islands of solids have developed. A well maintained pit will not have any significant crusting. If the material in the pit is not fluid or there are maggots visibly working on the surface, it's time for a clean out.
What about fly movement? Do flies typically move from the hog farm to other locations? The simple answer is no. Movement is limited. There have been a number of studies looking at the question of house fly dispersal in urban and agricultural settings. To summarize, fly numbers drop off dramatically at distances greater than 50 to 100 meters from breeding sites (e.g., dumpsters, poultry houses and cattle lots). When dispersal does occur, the tendency is toward other potential breeding sites. The consensus among researchers is that house flies will disperse no more than a mile under normal conditions. The perception of long distance dispersal from hog and poultry houses probably has more to do with relative fly density in a given area, weather events and nearby breeding sites that may go unnoticed (crop debris, dumps, kennels, small loafing pens and barns, poorly-maintained compost piles, etc.). It's important to point out, however, that the limited dispersal of filth flies is not an excuse to neglect fly management.
From time to time, insecticides may be needed to reduce fly numbers regardless of how well a farm is managed. One of the biggest mistakes made with chemical fly control is the way in which surface-applied insecticides are used. There are two things that usually go wrong: 1) placing spray where it's not effective; and 2) using the least effective formulation. The best outcome in either case is that the treatment will not control flies. Application of the right kind of surface spray to the right target can reduce labor, save money and minimize the risks to the environment.
Most of us don't adequately consider the formulation used to spray a surface for fly control. It does make a difference though. Making the correct choice depends on how porous the treated surface is. Where surfaces are porous (unpainted cement block and wood for example), a wettable powder formulation is generally the best choice. Once dry, wettable powders leave a more uniform residue on these rough, porous surfaces. Emulsifiable concentrates, on the other hand, are absorbed into porous materials and may not be as well distributed over the surface of porous building materials. Emulsifiable concentrates are equally effective on less porous surfaces such as painted blocks, metal and vinyl. Even though wettable powders are as effective in this case, they may be less desirable because they are harder to mix and require constant agitation.
Remember that regardless of the formulation used, rough, porous surfaces will need significantly more spray for thorough coverage than smooth, impervious surfaces. For example, cyfluthrin formulations used for fly control call for 1 gallon of spray (water) for each thousand square feet of painted plywood surface, compared to the recommendation of 2.7 gallons for a thousand square feet of unpainted plywood. Where painted cement block is to be treated, cyfluthrin labels still call for 3.2 gallons of spray per thousand square feet. Treatment of unpainted cement block calls for 36 gallons of spray for each thousand square feet!
Finally, fly sprays need to be targeted where they'll do the most good. Too often I see surface sprays for fly control applied to every available surface in swine buildings. This practice is wasteful and can be dangerous to non-target organisms. A more selective approach to the application of fly sprays significantly reduces risk and saves both labor and insecticide.
House flies tend to migrate upward at night. A large percentage will spend the evening resting on rafters and other overhead surfaces. That is the place to direct surface sprays. Alternatively, treatment under eaves and on the southern or eastern exposures of exterior walls will often yield good results. Southern and east-facing walls are particularly good treatment areas when evening temperatures are cool. Large numbers of flies gravitate to these exposures to warm up in the morning. It's simply not necessary to spray the entire building from top to bottom, inside and out. It pays to observe where flies tend to congregate in any building. Those are generally the only sites one needs to treat.
Other methods of fly control may be useful when fly populations are not extremely high. Baited traps, containing either a toxic bait or simply water to drown flies, can be effective. The recommendation for trap density is one to every 1,000 square feet of floor area. Fewer may be used if control is acceptable. Traps should be hung from the ceiling and be easily accessible. The biggest disadvantage to traps is that they must be cleaned and recharged regularly (about once a week) to remain effective. Traps should also be placed early in the season.
Electrocution traps can also be effective. Several types are
available for use in livestock buildings. They can be hung from
the ceiling or wall mounted at one or less per 1,000 square feet of
floor area. Maintenance is minimal, but the cost per trap is high
at around $500 each. Fortunately, the service life of these traps
is at least 5 to 10 years. The fluorescent UV lights used in these
traps will need to be replaced from time to time, of course.
Web page last updated on May 18, 1998 by Stephen J. Toth, Jr..