Spatial distribution of onion twister disease in major onion-growing regions of Karnataka

Abstract

Roving survey was conducted to assess the incidence of onion twister disease in major growing districts of Karnataka during 2022-23 and 2023-24 covering seven districts in the first year and five districts in the second, with systematic field sampling and disease scoring using a 0-5 scale. Per cent Disease Index (PDI) was calculated and GPS coordinates of each field were recorded for spatial mapping. During 2022-23, mean PDI ranged from 18.28 per cent in Dharwad to 45.14 per cent in Chitradurga, with major hotspots identified in Chitradurga and Chikkamagaluru. In 2023-24, disease incidence declined markedly, with average PDI across districts reduced to 6.69 per cent, indicating improved crop management and favorable climatic conditions. Spatial distribution maps highlighted significant variability in disease occurrence across taluks. Results underscore the importance of continuous surveillance and adoption of integrated management strategies.