Alternaria solani

Alternaria solani is a fungal pathogen, that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides.

Geographically, A. solani is problematic in tomato production areas east of the Rocky Mountains and is generally not an issue in the less humid Pacific or inter-mountain regions. A. solani is also present in most potato production regions every year but has a significant effect on yield only when frequent wetting of foliage favors symptom development.

Hosts and symptoms

Alternaria solani infects stems, leaves and fruits of tomato (Solanum lycopersicum L.), potato (S. tuberosum), eggplant (S. melongena L.), bell pepper and hot pepper (Capsicum spp.), and other members of the Solanum family. Distinguishing symptoms of A. solani include leaf spot and defoliation, which are most pronounced in the lower canopy. In some cases, A. solani may also cause damping off.