Infection usually occurs on the stem at or above the soil-line, however, all foliar parts of the plant can be affected. Dark brown, sunken lesions form at the base of the plant and eventually expand to girdle the stem, resulting in yellowing and wilting of the older leaves. As the wilting progresses the plant may eventually die.
The fungus can survive in the soil, in infected plant debris and seed, as well as on nightshade and other related hosts. Didymella stem rot occurs over a wide range of conditions, however, 20°C (60°F) accompanied by splashing water from rain or overhead irrigation is optimum for disease development and spread. Plants become more susceptible as they mature, and deficiency of soil nitrogen and phosphorus can contribute to disease severity.
