Impact of predisposing factors on development of stemphylium blight of garlic under Punjab conditions

Abstract

Effect of predisposing factors like leaf wetness duration, plant age, date of sowing, temperature, relative humidity, total rainfall and number of rainy days was studied on the severity of the Stemphylium blight of garlic (Stemphylium vesicarium). With an increase in the leaf wetness duration and age of plant, corresponding decrease in the incubation period and increase in the rate of disease progress was recorded. Minimum 8 hours of leaf wetness duration is required for the initiation of the disease under controlled conditions. Highest disease severity was found at 25ºC (63.11 per cent) followed by 30ºC (56.00 per cent) and 20ºC (49.78 per cent) and the disease progress ceased altogether at 15ºC. The rate of disease severity was less in the late sown crop (16th Nov) in comparison to early sown crop (10th oct, 26th Oct). Rainfall coupled with dry and warm weather was optimum for the growth of the pathogen which resulted in increased disease severity. Maximum and minimum temperature, maximum and minimum relative humidity, total rainfall and number of rainy days were positively correlated with the disease severity.