Factors Affecting Conidial Exudation and Survival, and Ascospore Germination of Leucostoma cincta . Radwan M. Barakat, Department of Plant Pathology, Washington State University, Pullman 99164. D. A. Johnson, and G. G. Grove, Department of Plant Pathology, Washington State University, Pullman 99164. PLANT DIS. 79:1245. Accepted for publication 27 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1245.

Conidia of Leucostoma cincta from sweet cherry were exuded from pyenidia at 2 to 28°C with an optimum exudation at 20°C. Free water was needed for exudation at incubation periods of 6 to 24 h at 20°C. Conidia were exuded at 100% relative humidity during 48 and 72 h of incubation. A large proportion of conidia in dried cirrhi survived summer conditions in the field. Ascospores germinated at 10 to 28°C with an optimum at 28°C during incubation times of 12 to 24 h. Conidia germinated at 15 to 28°C during an incubation period of 24 h. Maximum germination of conidia occurred at 28°C during 24 h of incubation. Conidia germinated at 5 to 20°C when incubation periods were extended to 48 and 72 h. Inoculations of sweet cherry trees with ascospores of L. cincta resulted in infection and development of stem cankers.