Studies on Development of Alternaria Blight on Rapeseed-Mustard and Spray Schedule of Fungicide for its Management

India is one of the largest rapeseed–mustard growing countries in the world occupying the third position in area and in production after China and Canada with 12% of world’s total production. Rapeseed-mustard is the second most important oilseed crop in the country after groundnut and accounts for nearly 30.7% of the total oilseed production in the country. At global level rapeseed–mustard is cultivated on 36.15 m ha with production of 71.09 MT. Alternaria blight caused by Alternaria brassicae and Alternaria brassicicola has become one of the important diseases of this crop in the country. This disease attacks on stems, leaves and pods. Partial resistance to Alternaria blight was observed in varieties GSL-5, Pusa aditya, Kiran, RH-479, Sheetal, GSL-2, GSL-1 as they are recorded with less number of spots/10 cm2, small size of spot, less sporulation, less per cent disease severity, less infection rate, less leaf defoliation and higher yield. The last appearance of disease was noted on genotype GSL-5, (53 DAS) followed by Kiran (52 DAS). Significantly lower per cent disease severity on leaves was recorded on cultivar GSL-5 (12.35%) followed by Kiran (14.12%), Pusa aditya (14.16%) and GSL-2 (15.37%), respectively. The minimum infection rate on leaves was recorded on cultivar GSL-5 (0.214) followed by Pusa aditya (0.218).The maximum infection rate was recorded on leaves on cultivar KBS-3 (0.229) followed by PS-66 and T-27 (0.228) respectively. In fungicidal management plot three sprays of Nativo 75 EC @ 0.08%, one at DI, second and third at 15 days intervals and three sprays of Nativo 75 EC @ 0.08%, one at DI, second at flowering and third at poding stage showed low per cent disease severity, low infection rate, higher yield and higher avoidable yield loss compared to other treatments. These treatment are proved to be effective compared to other treatments. While control plot showed high per cent disease severity, high infection rate, lower yield and lower avoidable yield loss compared to other treatments. The maximum benefit cost ratio (1:7.72) was obtained with two spray of Nativo 75 EC @ 0.08%, one at FS and second at poding stage followed by three spray of Nativo 75 EC @ 0.08%, one at DI, second and third at 15 days intervals (1:7.56). On the basis of above findings it may be concluded that Alternaria blight can causes extent of yield losses in yield of rapeseed-mustard up to 41.16% in eastern Uttar Pradesh. To manage the disease 3 sprays of Nativo @ 0.08 % was most economical and can be recommended to the farmers of blight prove areas.

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