Estimation of White Mold Disease Reduction of Yield and Yield Components of Dry Edible Beans

Abstract

Surveys conducted from 1970 through 1973 indicated that dry edible bean (Phaseolus vulgaris L.) plants in western Nebraska irrigated fields averaged 30% infection, and bean fields averaged 13% loss due to the white mold fungus, Sclerotinia sclerotiorum. Plants severely infected by S. sclerotiorum sustained a mean decrease in seed yield of 44% when compared to healthy plants. Total seed yield, and the components of yield, including number of seeds per plant, 100‐seed weight, and number of pods per plant, were significantly reduced by S. sclerotiorum. Reduced number of seeds per plant was the major component of yield loss followed by reduced weight of 100 seeds. Field conditions favoring vigorous foliage growth and high yields of Great Northern and Pinto bean types also favored white mold development. Thus, regression analysis indicated that low to moderate levels of infection by S. sclerotiorum were often associated with higher yields, but with a high percentage of infection yield reduction occurred. A second degree polynomial gave the best correlation of the data (r = 0.56). The assessment of disease losses due to S. sclerotiorum is discussed.