Natural and Experimental Production of Oospores of Bremia lactucae in Lettuce in New York. J. E. Yuen, Graduate Research Assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853. J. W. Lorbeer, Professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853. Plant Dis. 71:63-64. Accepted for publication 31 May 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0063.

Oospores of Bremia lactucae were observed in leaves of infected lettuce plants from commercial lettuce fields in New York. Oospores formed in cotyledons of the cultivar Ithaca after dual inoculation with isolates of opposite compatibility type. Two compatibility types were detected in New York. With one exception, each field sampled contained only one compatibility type.

Keyword(s): downy mildew, Lactuca sativa.