Temperature and Moisture Influences on Development of White Mold Disease (Sclerotinia sclerotiorum) on Great Northern Beans. A. Weiss, Assistant Professor of Agricultural Meteorology, University of Nebraska Panhandle Station, Scottsbluff 69361. E. D. Kerr, Professor of Plant Pathology, University of Nebraska Panhandle Station, Scottsbluff 69361; and J. R. Steadman, Associate Professor of Plant Pathology, Department of Plant Pathology, University of Nebraska, Lincoln 68583. Plant Dis. 64:757-759. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-757.

Great Northern dry edible beans (Phaseolus vulgaris) inoculated with a suspension of mycelial fragments of Sclerotinia sclerotiorum were incubated in a constant-temperature chamber at 100% relative humidity for periods up to 268 hr at 10–30 C. Percentage of diseased foliage was measured and expressed as a function of time and temperature. Air temperatures favorable for disease development ranged from 10 C to the optimum 25 C. Plants incubated at 30 C did not develop white mold. White mold did develop, although more slowly, on plants incubated at 25 C until symptoms first appeared, at 30 C for 24 hr, and then at 25 C. In a field experiment, air temperatures at 10-cm height were measured in Great Northern bean plots under normal and heavy irrigation treatments. Temperatures were favorable for white mold development 82 and 87% of the time in normal and heavy irrigation treatments, respectively. Disease incidence was about 13 times greater in the heavily irrigated plot than in the normally irrigated plot, indicating that duration of leaf moisture, rather than air temperature, limits white mold disease development in western Nebraska.