Effective fungicides on Olpidium brassicae causing lettuce big-vein disease and optimum drenching conditions

Abstract

To develop chemical control measures against lettuce (Lactuca sativa) big-vein disease (BV), 36 fungicides were tested for the effect on infectivity by Olpidium brassicae and the expression of lettuce big-vein symptom by drench treating. Thiophanatemethyl (TM) was effective with optimum conditions as follows: (i) the effective concentration of TM was more than 350ppm; (ii) soil around lettuce roots was saturated with ca. 50ml TM per 90ml pot; and (iii) treatment with TM on day of transplanting. The effects of TM persisted for ca. 1 month. No phytotoxicity were observed. From these results, TM application was effective during the initial growth period of lettuce for the control of lettuce big-vein disease.