For most commercial livestock operations manure management is THE most important variable in any fly control program simply because this is the largest single source of (from a fly’s perspective) “the good stuff”. But be aware that some biting flies reproduce in rotting vegetation, not manure. There are two variables with manure that you can most easily change. The first is the quantity of manure, the second is the moisture content of that manure.
Hauling manure at least a 1/4 mile away in the summer no less often than every seven days is one option. This distance and time is important as flies generally travel no more than 1/4 mile (they can go farther) and they take at least 8 days to go from an egg to an adult fly at summertime temperatures (85℉).
Rather than cleaning out the barn and then piling it right next to it (which ensures that ALL the flies coming off that manure will make it to your barn) stockpile it near where you will be spreading it, far away. If frequent hauling is not practical, then at least turn the moist edges of the pile weekly. The other things you can do with manure to make it less fly friendly are moisture control and temperature.
A fly larvae has to be in a medium that is between 40-60% moisture or it simply won’t complete its development. Increase the moisture of your manure by holding it in a liquid lagoon as a fly can’t reproduce underwater. But make sure that you do not let a solid cap form on that lagoon or you will have a huge fly factory there. The top of the cap will be too dry and the bottom next to the water will be too wet, but somewhere in the middle will be just the perfect moisture for optimum fly production. Not Good. The cost of diesel or electricity to agitate it regularly, or adding bacteria to help keep it liquid, or installing a solids separator can be great investments in fly control.
In areas that receive regular summer rains, one alternative to a lagoon is to collect the manure frequently and pile it. When you do this the manure that is deeper than six inches from the surface becomes too hot for a fly larvae to survive due to decomposition. So even if the pile is mountainous, only the outer surface will allow for fly reproduction. One big pile is better than a bunch of small piles as you are trying to minimize the surface area. To speed up the decomposition consider adding a compost turner like the one shown here.
For areas that receive little moisture during the summer a good choice is to dry the manure. Best is daily collection and spreading manure thinly on crop areas. Running a harrow or screen drag around your pens and pastures to break up the pats into smaller faster drying pieces can be very effective. Keep in mind that you are in a race with the flies as you want that manure to be less than 40% moisture by the 5th day from new or when it came out of the lagoon. This is because at the optimum temperature of approximately 85°F it takes at least 5 days for a pest fly to pupate (form its cocoon) which is a really critical time for the moisture level. If it’s drier than 40%, the fly’s puparium (cocoon) doesn’t form properly and that particular fly is toast.
Do the best you can to clean stalls, corrals, paddocks, pens, drainage areas, loafing sheds, calf barns, feeding aprons, spilled feed and other decaying organic matter at no more than a seven day interval to minimize fly breeding. It doesn’t take much material to produce a lot of flies. Daily pickup is preferred, but if you remove those pupae before the flies have emerged, (eight days minimum) the difference can be enormous.
Dr. Bill ClymerFort Dodge Animal Health, Dr. Roy EllisPrairie Pest Management, Dr. Kevin FloateAgriculture and Agri-Food Canada, Dr. Robert M. Miller, DVM, Dr. William QuarlesBio-Integral Resource Center. All illustrations 2006 Dr. Roy Ellis.
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