Early Blight in Tomatoes (Alternaria solani)

Symptoms

Early blight symptoms begin as oval-shaped lesions with a yellow chlorotic area along the lesion; concentric leaf lesions can be seen on infected leaves; leaf tissue between the veins is destroyed; severe infections can cause leaves to collapse completely; as the disease progresses, leaves burn severely, causing yield loss; tomato stems can be infected with the fungus leading to Alternaria stem canker; the first signs of root canker are the development of dark brown areas on the stem; root cankers can grow to encircle the entire stem, resulting in the death of the whole plant; brown streaks may be found in the vascular tissue above and below the canker area; fruit symptoms include small black v-shaped lesions on the shoulders of the fruit (the disease is also known as black shoulder); lesions may also appear as dark spots with concentric ring patterns on the fruit; fruit lesions that can be seen in the field or develop during fruit transit to market; lesions may have a velvety appearance due to the sporulation of the fungus.

Agent

Fungal

Disease Development Conditions

The disease can spread rapidly after plants bear fruit; the movement of airborne spores and contact with infested soil are the causes of the spread of the disease.

Control Methods

Apply appropriate fungicide at the first sign of the disease; destroy diseased plants; practice crop rotation.