Evaluation of Plant Extracts, Bioagents and Chitosan against Alternaria Leaf Spot of Asalio (Lepidium sativum L.) Caused by Alternaria burnsii

Abstract

Asalio or garden cress (Lepidium sativum L.) is a nutritionally and medicinally important herb affected by Alternaria leaf spot caused by Alternaria burnsii. The present study evaluated selected plant extracts and bioagents under in vitro conditions and chitosan under glasshouse conditions for disease management. Tulsi leaf extract (10%), ginger rhizome extract (10%), neem leaf extract (10%) and garlic bulb extract (10%) were assessed by the poisoned food technique. Trichoderma viride, T. harzianum, T. koningii and Pseudomonas fluorescens were evaluated by the dual culture method. Chitosan at 0.1, 0.2, 0.3 and 0.4% was evaluated in a growbag experiment. Garlic extract (10%) completely inhibited the mycelial growth of A. burnsii, recording 100.00% inhibition, while neem extract recorded 60.00% inhibition. Among the bioagents, T. viride was the most effective, with 86.52% inhibition, followed by T. harzianum and T. koningii. Under glasshouse conditions, chitosan at 0.4% recorded the lowest disease intensity after each spray and produced the highest disease reduction over the untreated control (58.09%). These results indicate that the evaluated plant extracts, bioagents and chitosan differed in efficacy against Alternaria leaf spot of Asalio. Garlic extract, T. viride and chitosan at 0.4% were the most effective treatments within their respective evaluations and warrant further assessment under integrated disease-management conditions.