Epidemiological factors in relation to development and prediction of Alternaria blight of rapeseed and mustard
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Authors
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R.P. AWASTHI and S.J. KOLTE
Department of Plant Pathology, G.B. Pant University of Agriculture & Technology, Pantnagar 263 145
Keywords:
Alternaria blight, rapeseed-rnustard, epidemiological factors, predictionAbstract
Multiple regression analysis (MRA) equations between weather parameters as independent factors and prediction of Alternaria blight (AB) severity as dependent factors on the most commonly grown susceptible rapeseed yellow sarson cv. T-151 and mustard cv. Varuna were established based on the data obtained over seven years crop periods (1980-1987). Total rainfall (RF) and minimum temperature (Mi TEMP) showed significant contribution in MRA equations, whereas combined effect of relative humidity (RH), RF, and Mi TEMP accounted for more than 98 per cent contribution for prediction of AB severity on leaves of both yellow sarson and mustard. Total rainy days (TRD), RH, maximum temperature (Max TEMP) and Mi TEMP showed significant contribution in MRA equation in AB severity on pods of mustard, whereas only the TRD factor showed significant effect for spread of pod infection in yellow sarson. RH (>67%), TRD (>6), RF (>70mm) and Mi TEMP (7 to 10°C) were found to be more conducive for AB severity on leaves, whereas the RH and TRD factors showed significant contribution for spread of pod infection. RH below 67 per cent was less conducive for severe development of the disease. The severity of AB increased beyond 30 days on age of both yellow sarson and mustard, and increased in the age was positively correlated Cr' = 0.777 to 0.980) with increase in the susceptibility of the crop, the maximum leaf disease severity being at rosette to flowering stage of the crop.
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