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Ecology and Epidemiology

Response Models for Conidiospore Germination and Germ Tube Elongation of Mycosphaerella fragariae as Influenced by Temperature and Moisture. V. J. Elliott, Formerly Department of Plant Pathology, University of California, Berkeley 94720, Present address: USDA, ARS Oxford Tobacco Research Laboratory, Oxford, NC 27565; Phytopathology 78:645-650. Accepted for publication 10 November 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-645.

The influence of temperature on conidiospore germination of Mycosphaerella fragariae was evaluated on water agar. Germination was modeled as a nonlinear logistic function of time. The logistic rate of germination, calculated from this model, showed a maximum rate at 22.4 C. The maximum fraction of germination was constant at 0.94 from 5 to 30 C but dropped sharply between 30 and 35 C. Moisture requirements for conidiospore germination were determined by incubation on glass slides held at different moisture conditions. No germination was seen below 98% relative humidity, and the germination rate at 98100% relative humidity did not differ from germination with free moisture. Germ tube elongation was evaluated on water agar over a temperature range of 537 C. The maximum rate of elongation was seen at 22.7 C with minimum and maximum growth near 5 and 37 C, respectively.

Additional keywords: common leaf spot, Fragaria ananassa, Ramularia tulasnei, strawberry.