Survival of Phytophthora infestans in Potato Stem Lesions at High Temperatures and Implications for Disease Forecasting. P. F. Kable, Principal Research Scientist, New South Wales Department of Agriculture, Agricultural Research Center, Yanco, N.S.W., 2704, Australia. D. R. MacKenzie, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 64:165-167. Accepted for publication 28 September 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-165.

The ability of Phytophthora infestans to produce sporangia in 7-day-old lesions in potato stems after exposure to constant temperatures of 30–40 C was examined. Constant 30 C temperature had no effect, but 32.5 C was lethal to some sporangia, and the rate of mortality increased with higher temperatures. The relationship between diminished survival and duration of temperature exposure was found, by regression analysis, to be best expressed by a negative exponent over time and varying with temperature. However, survival at 40 C appeared to decline linearly with time. These data indicate that the provision of BLITECAST (a computerized late blight forecasting system) that cancels infection periods when temperatures the following day are 30 C or above may need modification if the system is used in hot climates.

Keyword(s): epidemiology.