Role of weather variables in the development of Stemphylium blight of garlic

The role of weather variables, such as temperature and leaf wetness on the development of Stemphylium blight of garlic was studied by working out simple, partial and multiple correlation coefficient. The effect of leaf wetness duration on incubation period and disease development revealed that a minimum of 24 hrs of leaf wetness is important for infection to occur. The decrease in incubation period while increase in disease severity showed positive correlation between leaf wetness period and disease severity. To ascertain the relationship of sequential disease development with different weather parameters such as maximum temperature, minimum temperature, maximum relative humidity and minimum relative humidity, regression equation was also computed. Simple correlation coefficient between disease severity and individual weather parameter was positively correlated. The partial correlation coefficient between disease severity and maximum relative humidity was also positively related but their correlation was comparatively weak, whereas with minimum relative humidity, it was positively and strongly correlated.