The Suppression of Purple Stain of Soybean by Removal of the Diseased, Defoliated Leaves from Field during Cultivation

Purple stain of soybean is a seed-borne disease. In soybean (Glycine max (L.) Merr.) cultivation where diseased defoliated leaves serve as an inoculum source of purple stain (Cercospora kikuchii Matsumoto et Tomoyasu), the removal of infected leaves from the field remarkably suppressed the disease incidence on growing leaves compared to the ordinary cultivation where leaves are left in the field. This practice delayed the infection of newly developed leaves, decreased the number of diseased leaves per plant and the number of lesions per diseased leaf. Consequently, this reduction of inoculum potential in the field significantly depressed the incidence of the disease on pods and seeds.