Development of cross resistance in fungicide resistant isolates of Alternaria leaf blight pathogen of tomato in western Maharashtra

Abstract

The fungicide resistance isolates in Alternaria leaf blight pathogen on tomato crop were isolated from 10 districts of Maharashtra against eight fungicides namely Dithane-M-45, Blitox, Kavach, Bavistin, Captaf, Nativo, Ridomil and Score. The percentage disease intensity (PDI) of after 7th day of inoculation shows that the Kavach and Nativo resistant isolate induced the maximum PDI of 21.33 and 20.44 per cent. The minimum PDI was induced by Dithane-M-45 resistant isolates with the PDI of 14.67 per cent which was followed by Blitox with PDI of 16.89 per cent. The Bavistin resistant isolate had developed cross resistance isolate to all seven other above fungicide applied in the tomato field. The Captaf resistant isolate had shown cross resistant to all other fungicide accept Dithane-M-45.The development of fungicide resistance and cross resistance to other fungicides has a serious consequence in the management of this disease in Western Maharashtra.