RESUMEN
Alternaria leaf blight caused by Alternaria brassicae and Alternaria brassicola, is one of the most destructive diseases of mustard (Brassica campestris, B. juncea and B.napus) in West Bengal, causing considerable damages to the crop. The experiment was conducted under in vitro and in vivo conditions to see the effect of bio-agents, plant extracts and chemicals (fungicide and SAR compound) against Alternaria brassicae. Maximum inhibition in mycelial growth (95.56%) was observed with Mancozeb 75% Wp followed by Lantana camera (80%), Salicylic acid (73.33%), Allium sativum (54.44%) and Zingiber officinale (17.78%) in comparison to control. Foliar spray with fungicide (Mancozeb 75% WP @ 0.2%) was found to be most effective in reducing disease severity (81,23%) and infection rate which increased the yield (77.23%) of mustard over untreated control. Among the plant extracts, Lantana camera was found to be excellent in controlling the Alternaria blight infection in the field (71.92% reduction in disease severity and 68.18% increase in yield) in comparison to salicylic acid (SAR compound) and bio-agent (Trichoderma viride) 48.33% and 36.27% reduction in disease severity respectively.