Effect of Azoxystrobin 8.3%w/w + Mancozeb 68.75% on Powdery and Downy mildew Pathogens under In vitro condition

Field surveys were conducted in 3 major grapevine growing districts in Tamil Nadu viz., Coimbatore, Theni and Dindugal. The downy mildew infection on leaves was the highest (PDI 76.92 in Cumbum of Theni district. In the survey on the incidence of powdery mildew showed that the highest incidence of PDI on leaves, inflorescence and fruits in Cumbum of Theni with records of 65.49, 63.56, 61.23 percent. The pathogenecity test revealed that the downy mildew isolate D-TC1 of Theni district was found to be more virulent with highest PDI of (42.35). The powdery mildew isolate of Cumbum (P-TC1) of Theni district was found to be more virulent by recording the maximum PDI of (36.94). Among the different fungicide tested against spore germination of P.viticola, Azoxystrobin 8.3%w/w + Mancozeb 68.75 at 0.36 per cent recorded 89.26 % inhibition . The fungicide Azoxystrobin 8.3% + Mancozeb 68.75 in all three concentrations, was found to be superior in inhibiting the spore germination of U. necator by recording 90.27%, 89.91%, 80.70% respectively in 0.36, 0.30 and 0.24 % concentrations.