EVALUATION OF 2 METHODS FOR RELEASE OF ENTOMOPHTHORA-MUSCAE (ENTOMOPHTHORALES, ENTOMOPHTHORACEAE) TO INFECT HOUSE-FLIES (DIPTERA, MUSCIDAE) ON DAIRY FARMS

Two methods for initiating epizootics of Entomophthora muscae (Cohn) Fresenius in house fly, Musca domestica L., populations were evaluated on New York dairy farms. First, 500 fresh, laboratory-infected fly cadavers were placed weekly for 10 wk inside barns in areas of high fly activity. Second, 2,500 living, infected flies were released on each of two occasions spaced 3 wk apart. Releases were started in mid-june. Three farms were used for each treatment plus three control farms. The E. muscae used for the releases had been isolated from house flies collected from dairies the year before and had been maintained by continuous fly-to-fly passage. Prevalence rates on both types of E. muscae release farms were twice as high (23-28%) as on control farms (12%) in the weeks after the start of the releases. Releases were more effective OD farms with high fly populations than on farms with low fly populations. Examination of conidia indicated that the released strain (8-18 nuclei per conidium) became established as a result of the releases. Epizootics occurred on all farms, including controls, in September through November. Infections in the spring were exclusively with a strain of E. muscae with 2-8 nuclei per conidium; by fall, most infections (86-93%) were with a strain with 8-18 nuclei per conidium, even on control farms. Nuclear densities in the laboratory culture remained constant at 8-18 nuclei per conidium during this shift in wild infections. Neither of the E. muscae treatments significantly reduced fly populations.