Management of premature leaf fall (Marssonina coronaria) of apple with new generation fungicides in the North‐Western Himalayan Region of India

Abstract

AbstractIn the north‐western Himalayan region of India, premature leaf fall (PLF) caused by Marssonina coronaria is a major disease in apple orchards. Field experiments were conducted at a commercial orchard to evaluate the efficacy of new‐generation fungicides on PLF management during 2018 and 2019. Three contact fungicides (chlorothalonil, propineb and mancozeb), one systemic fungicide (difenoconazole) and four combination products (metiram +pyraclostrobin, fluxapyroxad +pyraclostrobin, tebuconazole +trifloxystrobin and fluopyram +tebuconazole) were evaluated against an untreated control (UTC) by applying them at three times at 15‐day intervals to trees of the susceptible apple cultivar ‘Royal Delicious’. Out of all tested treatments, tebuconazole +trifloxystrobin achieved the lowest area under disease progress curve (AUDPC) and the greatest yield increase. Similarly fluxapyroxad +pyraclostrobin and fluopyram +tebuconazole also significantly reduced AUDPC and enhanced yield relative to the UTC. Taking into account the cost of the tested products, tebuconazole +trifloxystrobin offered the best benefit‐cost ratio in both years, followed by fluxapyroxad +pyraclostrobin and fluopyram +tebuconazole. Based on these findings, the combination products tebuconazole +trifloxystrobin, fluxapyroxad +pyraclostrobin and fluopyram +tebuconazole can all be recommended to the farmers of the north‐western Himalayan region for PLF management.