Early blight is a fungal disease of tomato (Lycopersicon esculentum Mill). It is an important disease of tomato which is caused by Alternaria solani (Ellis & Mart.) and Alternaria alternate f.sp. lycopersici. Tomato crop is damaged due to severe infection of A. solani every year in India. It is also a common problem in United Kingdom, Australia and United State. The yield loss of tomato fruit was 80% recorded at 72% disease intensity of A. solani and each 1% increase reduced tomato yield by 1.36%. It is also one of the most common causes of seedling blight or damping off in tomato, causing dark lesions on the rootlets. It is three phase disease which can produce leaf spot, stem canker and fruit rot. But the foliar phase is the most common and destructive part of the disease.