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Stable flies are serious, blood-feeding, pests of livestock, especially cattle, throughout much of the world. Their painful bites reduce livestock productivity, cause pain and suffering in companion animals, and disrupt human recreation. Both male and female stable flies require blood for sexual maturation and reproduction and will blood-feed one or more times per day for their entire adult life of up to three weeks. Immature stable flies develop in decomposing vegetative materials, especially those associated with animal wastes. Throughout much of the northcentral United States, cattle producers feed their animals hay from large round bales during the winter. As the animals feed, much of the hay falls to the ground and is wasted. When combined with manure and urine from the cattle, this material produces an ideal substrate for the development of stable flies. More than one million flies can develop in a single hay feeding site and producers will frequently have several feeding sites in each pasture. The hay feeding site substrate is highly organic and microbiologically very active. Most pesticides break-down rapidly and have little or no residual activity in this type of material. Cyromazine is an Insect Growth Regulator which interferes with chitin synthesis and inhibits molting. Treated immature insects cannot develop into the next stage or molt into adults. Unlike most insecticides, Cyromazine does not break down rapidly in organic substrates. In fact, Cyromazine can be used as a feed-through for the control of flies developing in fresh manure. Liquid and granular formulations of Cyromazine can effectively control flies in animal waste associated with confined cattle and swine production systems.<P> Previous studies in eastern Nebraska have shown that stable flies begin colonizing hay feeding sites in March and adult emergence begins in mid May followed by peak adult emergence in mid June through early July. Fly emergence from the sites declines to very low levels in late July and remain there for the remainder of the year. The hay feeding sites appear to be the primary source of stable flies during the early summer months in eastern Nebraska. The objective of this study will be to evaluate the efficacy of a single treatment with Cyromazine to control adult stable fly emergence from winter hay feeding sites.
Six winter hay feeding sites will be identified and partitioned into halves along a line that produces the greatest degree of symmetry as determined visually. One half at each site, chosen randomly, will be treated with 25 g of Neporex 2 SG granules per square meter (=0.5 g Cyromazine / square meter) on approximately 1 May. Control halves will remain untreated. Three emergence traps (0.5 x 0.5 m) will be placed on each half of each site on approximately 15 May. Sites will be enclosed with electric fence to exclude cattle. Traps will be serviced twice weekly and relocated every 2 weeks through approximately 31 July. Collected flies will be sexed and counted. Differences in collections from emergence traps in treated and control areas will be evaluated with Poisson Regression. Temporal differences in emergence patterns will be evaluated by comparisons of empirical distribution functions with the Kolmogorov-Smirnov Test.