A comprehensive study of the status and strategic management of downy mildew of onion (Allium cepa L.) in Kashmir Valley

Onion, one of the most important commercial vegetable crops is affected by the most destructive disease known as Downy mildew. It is the most serious and devastating disease of the onion seed crop in the temperate zones of Jammu and Kashmir, limiting the quality and quantity of both bulb and seed. The disease occurs year after year in epiphytotic form taking lion’s share of the produce. Therefore, detailed investigations were undertaken with the objectives to record disease incidence and severity in different districts of Kashmir valley and also devise suitable management strategies with chemicals and botanicals. Survey the year 2020, revealed that the disease was prevalent in Kashmir valley ranging from 30.90 to 37.65 per cent. The highest disease incidence was recorded in district Budgam (35.09%) and minimum in district Srinagar (23.73%). The severity ranged from 13.12 to15.2 per cent, maximum in district Budgam (14.88%) and minimum in district Srinagar (9.99%). The pathogen was identified on the basis of morphological features as Peronospora destructor (Berk.) Casp. Ex Berk. Sporangiophores were dichotomously branched with size varying from 122-820 × 7-18 µm and pyriform/ fusiform sporangia measuring 53.6-62.8 µm in length and 24.8-25.0 µm in width. Efficacy study of different fungicides and botanicals revealed that amongst the fungicides two formulations Metalaxyl 4% + Mancozeb (64%) 68n WG, followed by Metiram 55% + Pyraclostrobin 5% 60 WG (74.04%) were most efficacious, while of the tested botanicals, extract of Allium sativum (Garlic) proved to be the most efficient with disease control of 44.39 per cent followed by Rheum emodi (Rhubarb) (41.14%).