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Ecology and Epidemiology

Survival of Detached Sporangia of Peronospora destructor and Peronospora tabacina. Esther Bashi, Department of Ecology and Climatology, The Connecticut Agricultural Experiment Station, P. O. Box 1106, New Haven, CT 06504, Senior author on leave from Volcani Center, Bet-Dagan, Israel; Donald E. Aylor, Department of Ecology and Climatology, The Connecticut Agricultural Experiment Station, P. O. Box 1106, New Haven, CT 06504. Phytopathology 73:1135-1139. Accepted for publication 3 March 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1135.

Detached sporangia of Peronospora destructor were exposed for various lengths of time to different laboratory combinations of temperature and relative humidity (RH); temperatures of 10, 25, and 35 C were used in combination with 33, 53, 76, and 95% RH. Germination indicated survival. For all RH tested, P. destructor sporangia survived best at 10 C and poorest at 35 C. For all temperatures tested, sporangia survived poorest at 33% RH, and differences in survival between 53 and 76% RH generally were not significant. Sporangia of P. destructor and P. tabacina were also exposed outdoors on cloudy or sunny days before being put into standard conditions to germinate. Of temperature, RH, and sunlight, sunlight was the most important factor in determining sporangia survival. On cloudy days, the average germination of detached sporangia of P. destructor was reduced from 83 to 68% in 6 hr, whereas on clear, sunny days germination was reduced from 46 to 0% in 6 hr. The effect of solar irradiation on the germination of sporangia of P. tabacina was similar to that for sporangia of P. destructor.