VIEW ARTICLE

Ecology and Epidemiology

Effects of Inoculum Level of Rhizoctonia solani on Emergence, Plant Development, and Yield of Dry Beans. A. H. C. van Bruggen, Former graduate research assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853, Present address: Department of Plant Pathology, University of California, Davis 95616; C. H. Whalen(2), and P. A. Arneson(3). (2)(3)Technician, and professor, respectively, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853. Phytopathology 76:869-873. Accepted for publication 22 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-869.

The effect of inoculum density of Rhizoctonia solani on hypocotyl infection, plant development, and yield of dry beans was evaluated in two field experiments using microplots. Fumigated soil was mechanically mixed with 0-800 sclerotia per kilogram of soil. The population means of the periods from sowing to emergence, flowering, and podset increased linearly with inoculum level. The proportion of plants infected, numbers of lesions, and lesion areas increased with higher inoculum levels in the form of a saturation curve, the maximum being reached at 250-350 sclerotia per kilogram of soil. Of the yield components, only the numbers of plants per plot decreased significantly with increasing inoculum densities, and the overall yield was not affected by level of infestation (100-800 sclerotia per kilogram of soil). Initial number of lesions per hypocotyl was the only disease measurement that was negatively correlated with yield.