Effect of temperature, biofungicides and fungicides on clubroot of selected brassica crops
Clubroot is an economically important disease of Brassica crops caused by the soil-borne protist 'Plasmodiophora brassicae' Woronin. Shanghai pak choy was identified as a model crop for the study of clubroot on canola. The Rapid Cycling Brassica lines of 'Brassica carinata' and 'B. juncea', and two canola lines 46A65 and 46A76 were susceptible to pathotype 6 in Ontario. Controlled environment and field trials demonstrated that low temperature (<= 17° C) reduced initial infection and clubroot development. Severe clubroot was observed at temperatures 19.6°-25.5° C. Drench application of the biofungicides Mycostop® and Actinovate® and the fungicides Allegro® 500F and Ranman® 400 SC reduced clubroot severity in Shanghai pak choy under controlled conditions. Ranman application was effective when disease pressure was moderate to high. Fungicide application is not needed when there is a low risk of clubroot as a result of cool soil temperatures early or late in the season.