Progress and Spread of Dark Leaf Spot in Cabbage

Abstract

The progress and spread of dark leaf spot (Alternaria brassicicola) in three cultivars of cabbage (Brassica oleracea var. capitata) were characterized in two seasons. The intensification of disease in time at each of six points along a gradient from a line source of diseased plants resulted in disease progress curves that were almost symmetrically sigmoidal. Three growth models (logistic, Gompertz, and Weibull) were fitted to the severity values by nonlinear regression. The shape parameter (c) for the Weibull function averaged 3.61 (ranged from 2.40 to 6.36) (.)