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Effect of Bacillus cereus UW85 on the Yield of Soybean at Two Field Sites in Wisconsin. Robert M. Osburn, LiphaTech Inc., 3101 West Custer Ave., Milwaukee, Wisconsin 53209. Jocelyn L. Milner, Department of Plant Pathology, University of Wisconsin - Madison 53706, Edward S. Oplinger, Department of Agronomy, University of Wisconsin - Madison 53706, R. Stewart Smith, LiphaTech Inc., 3101 West Custer Ave., Milwaukee, Wisconsin 53209, and Jo Handelsman, Department of Plant Pathology, University of Wisconsin -Madison 53706. Plant Dis. 79:551-556. Accepted for publication 9 March 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0551.

Bacillus cereus strain UW85 was evaluated for its effect on the yield of three cultivars of soy-bean (Glycine max) over five seasons at two Wisconsin field sites where Phytophthora sojae was present naturally and that had low to severe disease potential for Phytophthora damping-off and root rot. The soybean cultivars, selected on the basis of genetic resistance to Phy-tophthora root rot, were 29725-15G (susceptible), DSR-262 (tolerant), and Elgin 87 (resistant, Rpsl-k allele). Soybeans were treated at planting with spore-based formulations of B. cereus or metalaxyl, applied in-furrow or to the seed. At Racine, Wisconsin, higher soybean yields were consistently associated with the genetically tolerant and resistant cultivars. Certain B. cereus treatments provided a significant yield benefit for the susceptible cultivar in all five growing seasons, and for all cultivars in 1990 when the disease pressure was especially high. At White-water, Wisconsin, higher yields were not associated with genetic resistance to Phytophthora root rot and there was evidence of pre-emergence damping-off. For the susceptible cultivar, yields for B. cereus treatments and metalaxyl did not differ significantly from the untreated control except in 1990, when yield and stand counts benefited from those treatments. Yield of the resistant cultivar was improved significantly by treatment with either B. cereus or metalaxyl in 1990, 1991, and 1992. The formulation of B. cereus influenced efficacy: clay granule formu-lations of UW85 applied in-furrow were the most consistent, but no single formulation of either B. cereus or metalaxyl exhibited efficacy at both sites and in all years. These data suggest that B. cereus improved soybean yield under conditions in which Phytophthora root rot influenced yield as well as under conditions in which other factors influenced yield

Keyword(s): biocontrol, biological control, zwiltermicin A