Influence of environmental factors on Alternaria blight

factors prevalent under field conditions. There were significant differences in the mean cumulative increase in lesion size of Alternaria blight on clusterbean varieties, HG-75, HG-365, RGC-936 and FS-277 during kharif 1997 and 1998. However, maximum periodical increase in lesion size was observed on highly susceptible variety, FS-277. Relative humidity evening and sunshine were found significantly associated negatively and positively, respectively with lesion size development. Minimum temperature was significantly negatively correlated with the lesion size development during 1997 while cumulative rainfall was found to be significantly directly associated during 1998. Key words: Clusterbean, Alternaria blight, disease progression, environment, correlation, regression Environmental factors play important role in the development of the disease. The environmental vari-ables viz., temperature, humidity, rainfall and sunshine are the most crucial, since they affect the pathogen, host or host pathogen interaction during pathogenesis. For disease prediction, quantitative relationship between disease development and weather variables has been established in several host-pathogen systems. However