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Influence of Green Manure Crops and Lettuce on Sclerotial Populations of Sclerotinia minor. H. R. Dillard, University of California, Davis 95616. R. G. Grogan, University of California, Davis 95616. Plant Dis. 69:579-582. Accepted for publication 29 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-579.

Continuous lettuce cropping resulted in the greatest mean inoculum density and proportion of soil samples with seven or more sclerotia of Sclerotinia minor during the 1-yr test period. In most plots, the frequency distribution of sclerotia among soil samples was best described by the negative binomial distribution. Of 50 data sets, only five had variance-to-mean ratios not greater than unity. Disease incidence in lettuce was greatest in plots previously planted to lettuce, vetch, or vetch/rye mix in the furrow-irrigated field and in plots previously planted to lettuce or vetch in the sprinkler-irrigated field.