Effects of Temperature and Wetness Duration on Sporulation of Botrytis cinerea on Strawberry Leaf Residues. M. Sosa-Alvarez, Former Graduate Fellow, and Professors, respectively, Depart-ment of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. L. V. Madden, and M. A. Ellis, Former Graduate Fellow, and Professors, respectively, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Plant Dis. 79:609-615. Accepted for publication 4 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0609.

Disks cut from dead strawberry leaves (autoclaved or air-dried) were inoculated with a conidial suspension of Botrytis cinerea (106 conidia per ml) and incubated at various temperatures (T) ranging from 5 to 30°C. Sporulation (conidia per cm2) on leaf disks was determined after exposure to wetness durations (W) of 3 to II days. Optimum temperature for sporulation was between 17 and 18°C at all wetness durations. Sporulation levels of 105 to 107 conidia per cm2 were observed between 15 and 22°C, after 7 days of continuous wetness. As temperature increased or decreased from the optimum, sporulation decreased for the same wetness durations. Very little sporulation was observed at 25"C and no sporulation was observed at 30?C. Loga-rithmic polynomial models best described the effect of T and W on sporulation of B. cinerea on dead strawberry leaf tissue. Coefficients of determination for data from all repetitions of the experiments were at least 0.81. The latent period of B. cinerea on dead leaf tissue was longest at the lowest temperature (6 to 7 days at 5°C) and decreased to <3 days as temperature in-creased to the optimum (15 to 22°C). Interrupted wet and dry periods of 5, 12, and 24 h directly affected sporulation. Total hours of wetness and the duration of individual wet periods had the greatest effect on the amount of inoculum produced at 20°C

Keyword(s): Fragaria x ananassa, gray mold, quantitative epidemiology