Abstract
Effect of five sowing dates and four different cultivars of mustard (Brassica spp.) on the incidence of alternaria leaf blight caused by Alternaria brassicae (Berk.) Sacc. and A. brassicicola (Schw.) Wilts. were studied. Lowest disease index and highest seed yield were studied. Lowest disease index and highest seed yield were obtained from 20th November 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 cultivars varied significantly (p = 0.01) in respect of disease index. Lower disease Indices were from Nap-3 and #5004. The cultivars SS-75 and #5004 produced higher seed yield in spite of disease incidence. The progress of disease was positively correlated (r = 0.99) with plant age.