Effect of epidemiological factors on alternaria blight of senna (Cassia angustifolia vahl.)

Intensity of Alternaria blight of Cassia angustifolia, caused by Alternaria alternata, was monitored in kharif 2004 and 2005 at fortnightly intervals vis-à-vis environmental factors (temperature, relative humidity & rainfall). The disease intensity in the two seasons varied between 3.2 to 23.5%. Comparatively higher disease intensity was observed during the months of July and September in both the years. The correlation studies suggested that R.H. was a key factor for development of the disease. The pathogen survived only up to 8 months under natural conditions but up to 10 months in vitro. On inoculation, eight weeks old plants showed maximum leaf blight as compared to young/older plants. Six to eight days old culture of A. alternata showed maximum virulence.