Kresoxim methyl SC-a Quinone Outside Inhibitor against Major Fungal Foliar Diseases of Apple

Abstract

Scab and Alternaria leaf blotch are the major destructive diseases of apple causing enormous loss to apple orchards of Kashmir and other states of India. The present study reports the bio-efficacy of kresoxim methyl 44.3 gL−1SC-a quinone outside inhibitor (QOI), against these diseases. The fungicide was evaluated at 0.03, 0.04 and 0.05 per cent concentrations at two different locations for two consecutive years (2014 and 2015) under epiphytotic conditions of Kashmir valley. The performance was compared with recommended standard fungicides viz., tebuconazole 25.9 EC, hexaconazole 5 EC and difenaconazole 25 EC at 0.05, 0.05 and 0.03 per cent concentrations, respectively, besides the water sprayed trees as check. The fungicide, during both the seasons and at both the locations, provided the best protection against scab and Alternaria leaf blotch. The trees treated with kresoxim methyl at 0.05 per cent concentration provided 97.25 and 97.70 per cent control of leaf scab incidence and intensity as against 95.72 and 97.43, 88.70 and 91.47 and 77.70 and 78.89 per cent observed in standards difenaconazole 25 EC, tebuconazole and hexaconazole respectively. The fungicide was significantly superior to standards tebuconazole 25.9 EC and hexaconazole 5 EC and was statistically at par with difenaconazole. Similarly, the fungicide gave an average fruit scab control of 98.00 and 98.48 per cent in incidence and intensity as against 97.25 and 97.60, 92.18 and 93.63, and 83.54 and 87.20 per cent recorded in standard difenaconazole, tebuconazole and hexaconazole, respectively. At 0.05 per cent concentration it performed efficiently in controlling Alternaria leaf blotch of apple with 94.65 and 95.20 per cent in incidence and intensity as against 94.65, 89.80 and 84.70 per cent in incidence with an intensity of 96.10, 90.56 and 85.03 per cent achieved with difenaconazole, tebuconazole and hexaconazole sprayed trees, respectively. Thus, based on two year data at two locations and comparison with the standards, it was concluded that use of kresoxim methyl at 0.04 to 0.05 per cent concentrations is effective in controlling leaf/fruit scab and Alternaria leaf blotch diseases of apple. Phytotoxicity study with the test fungicide carried out at 0.05 and 0.1 per cent concentrations on commercial apple cultivars (Red delicious and Red chief) during both the seasons and locations, revealed no sign of toxicity on fruits, leaves and other parts of the trees.