Efficacy of Eco-friendly Products in Managing Cucumber Downy Mildew and Inducing Biochemical Defence Responses

Downy mildew of cucumber (Cucumis sativus L.), caused by Pseudoperonospora cubensis, is a destructive disease responsible for severe yield losses under humid agro-climatic conditions. Continuous use of chemical fungicides has resulted in resistance development, phytotoxicity, and environmental concerns, necessitating the evaluation of eco-friendly disease management approaches. A field experiment was conducted during summer 2023 at the Vegetable Research Station, C. P. College of Agriculture, SDAU, Sardar krushinagar, to assess the efficacy of organic products, milk-based formulations, and systemic acquired resistance (SAR) inducers against cucumber downy mildew. The experiment was laid out in a Randomized Block Design with eight treatments, comprising salicylic acid (1%), isonicotinic acid (1%), sodium bicarbonate (1%), Panchgavya (10%), Jivamrut (10%), full cream milk (10%), buttermilk (10%), and an untreated control. Disease intensity, area under disease progress curve (AUDPC), fruit yield, and biochemical parameters were recorded. Among the treatments, salicylic acid (1%) recorded the minimum disease intensity (26.74%), lowest AUDPC (569.39), and maximum fruit yield (126.89 q ha⁻¹), followed by isonicotinic acid and sodium bicarbonate. All treatments significantly reduced disease severity and improved yield over the control. Increased peroxidase, polyphenol oxidase activities, and chlorophyll content in treated plants indicated activation of host defense responses. The study demonstrates that SAR inducers, particularly salicylic acid, offer an effective and environmentally sustainable alternative for managing cucumber downy mildew.