In vitro evaluation of various fungicides against Alternaria brassicae, causing leaf blight of mustard

Indian mustard (Brassica juncea L. Czern), an important oilseed crop in India, is greatly affected by Alternaria blight, predominantly caused by Alternaria brassicae, which serves as the chief pathogen. The disease may lead to significant yield losses of up to 45-47% in the Indian subcontinent by reducing seed quality, oil content, and market value. Therefore, the present study was undertaken to evaluate the efficacy of six fungicides, namely Mancozeb, Carbendazim, Mancozeb + Carbendazim, Azoxystrobin, Difenoconazole, and Tebuconazole, against A. brassicae under in vitro conditions using the poisoned food technique. The findings showed clear differences in the antifungal effectiveness of the evaluated fungicides. Among different fungicide formulations tested (i.e., Mancozeb, Carbendazim, Mancozeb + Carbendazim, Azoxystrobin, Difenoconazole, and Tebuconazole), Difenoconazole exhibited the highest percent inhibition (89.56%), followed by Tebuconazole (65.85%) and Azoxystrobin (51.28%). While, both Carbendazim and Mancozeb showed moderate suppression, yet their combination displayed only limited improvement over the individual fungicides. Overall, triazole fungicides proved more effective than the contact and systemic fungicides evaluated in this study. The results indicate that Difenoconazole, Azoxystrobin, and Tebuconazole hold strong potential for incorporation into integrated disease management strategies.