Symptoms

Symptoms on foliage

There are clearly delimited necrotic spots, of variable size which are mainly located on the bottom leaves and concentric rings on the larger spots (photos 1 to 3). Symptoms usually appear on the bottom part of the plant where the leaves are older and start senescing (photo 3 to 6)

Early blight symptoms may vary greatly from one growing environment to another. The type of potato cultivar may also contribute to different expressions of the disease but, until now, no clear link between the Alternaria species and the type of symptoms has been demonstrated.

Symptoms on tubers

The affected tubers are very dry and depressed (photo 7) and show brown to black superficial rot.