Numbers and distribution of apothecia of Sclerotinia sclerotiorum in relation to white mold of white bean (Phaseolus vulgaris)

Abstract

Relationships between the distribution and numbers of apothecia of Sclerotinia sclerotiorum (Lib.) de Bary and the distribution and incidence of white mold of white bean (Phaseolus vulgaris L.) were investigated in a field plot at Arkell, Ont., in 1981 and 1982. The spatial distributions of both apothecia and disease were aggregated and were most consistently described by the negative binomial distribution, although the Poisson, Poisson binomial and logarithmic with zeros distributions were also significant for some sampling dates. Numbers of apothecia were correlated with disease incidence within areas 1.4 (r = 0.07–0.67), 36 (r = 0.11–0.72), and 108 m2 (r = 0.21–0.95). The quantitative relationships between apothecia within a field of beans and the incidence of white mold may be useful in predicting the disease.