Survey on Incidence of Gummy Stem Blight on Watermelon (Citrullus lanatus) in Karnataka, India

Watermelon (Citrullus lanatus) is an important cucurbitaceous crop cultivated worldwide. The cultivation of watermelon and other species of the family Cucurbitaceae is severely affected by several diseases like anthracnose, Alternaria leaf spot, bacterial fruit blotch, powdery mildew and gummy stem blight. Among the diseases, gummy stem blight is an emerging and devastating disease caused by Didymella bryoniae producing a serious threat to the economics of production of cucurbits like watermelon. A roving survey was carried out in eight districts of Karnataka (Chamarajanagara, Chikkaballapura, Gulburga, Vijayapur, Bengaluru urban, Kolar, Mysuru and Yadgiri) from 2021 to 2023 to record the incidence of gummy stem blight (GSB) disease on watermelon. The survey data revealed that GSB disease was observed in all areas. The per cent disease index ranged from 29.6 to 51.2 per cent. The maximum mean per cent disease index of (51.2%),) Bengaluru urban district and the lowest was seen in the Mysuru district (29.6%) followed by Chikkaballapura district (31.0%). The pathogen associated with gummy stem blight disease was isolated and proved the pathogenicity of the isolate and fulfilled the Koch’s postulates.