EFFECT OF SOWING DATES AND CULTIVARS ON THE INCIDENCE OF ALTERNARIA LEAF-BLIGHT OF MUSTARD AT CHITTAGONG

Effect of five sowing dates and four different cultivars of mustard (B rassica spp.) on the incidence of alternaria leaf blight caused by Alt ernaria brassicae (Berk.) Sacc. and A. brassicicola (Schw.) Wilts. wer e studied. Lowest disease index and highest seed yield were studied. L owest disease index and highest seed yield were obtained from 20th Nov ember sowing. Sowings, before and after 20th November, lead to higher disease index and lower seed yield. Significantly negative correlation (r = - 0.92) existed between disease index and seed yield. Mustard cu ltivars varied significantly (p = 0.01) in respect of disease index. L ower disease Indices were from Nap-3 and #5004. The cultivars SS-75 an d #5004 produced higher seed yield in spite of disease incidence. The progress of disease was positively correlated (r = 0.99) with plant ag e.