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Ecology and Epidemiology

Longevity of Conidia of Sirococcus clavigignenti-juglandacearum in a Simulated Airborne State. N. Tisserat, Former graduate research assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; J. E. Kuntz, professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 73:1628-1631. Accepted for publication 21 June 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/Phyto-73-1628.

Longevity of rain-dispersed conidia of Sirococcus clavigignenti-juglandacearum in a simulated airborne state was studied in the laboratory and forest by impacting conidia on fine spiderweb threads wound around rectangular frames. Frames bearing conidia were exposed to different controlled vapor pressure deficit (VPD) and temperature levels. After 32 hr of exposure to still air at 13 C, 81% of the conidia were viable at 9.7 mb VPD compared to 11% at <0.8 mb VPD. At 25 C, 14% of the conidia survived for 32 hr at 20.6 mb VPD while less than 2% were viable at <1.3 mb VPD. In field tests, spore longevity varied greatly with weather conditions. The highest percentage survival in any field experiment was 35% after 8 hr on a cool, rainy day with overcast skies.