Effect of weather parameters on karnal bunt disease in wheat in Karnal region of Haryana

Data pertaining to average infection (%) of karnal bunt disease of wheat and meteorological parameters of 1st to 12th standard meteorological week (1st January to 25th March) for 25 crop seasons (1981-82 to 2004-05) of Karnal station were correlated to study the effect of weather parameters on Karnal bunt disease in wheat for most sensitive crop growth period corresponding to ear emergence and subsequent growth stages. The frequency of disease intensity and weather parameters indicated that when the maximum temperature exceeded normal accompanied by little or poor rainfall during 6 to 8th SMW, the disease intensity was low. Rainfall during the 3rd week of January showed strong relationship indicating favourable role in the formation and further multiplication of secondary spordia. However, during 9th SMW, maximum temperature, relative humidity, rainfall and sunshine duration showed considerably high correlations, whereas remaining parameters had weak correlation coefficients. Meteorological parameters during 6 to 12 SMW satisfactorily explained the occurrence of Karnal bunt disease with R2 values of 0.84 that indicated only 16% variation of disease remained unaccounted.