Stands are poor, plants appear sickly, and leaves wilt and die. This fungus also causes a stem rot in tomatoes. Seed cutting knives and equipment not cleaned after cutting infected tubers can contaminate healthy tubers. Bacteria may be spread in the field by seed corn maggots or seed potato maggots which have fed on infected plants. Planting only disease-free certified seed, sterilizing seed cutting knives and equipment, and controlling maggots reduces the incidence of blackleg.
Cereal crops are excellent rotational crop choices.
Early blight affects both tomatoes and potatoes. Symptoms include collar rot of seedlings, and leaf spots or blight which can defoliate the plants. Distinctive symptomatic features are the 'bulls-eye' appearance of leaf spots, and defoliation starting at the base of the plant. In tomatoes, early blight development can be restricted by maintaining plants in a vigorous state, minimizing injury to the plants and limiting the time leaves are wet. Staking or trellising tomatoes facilitates better airflow around plants and improves fungicide coverage, thereby slowing the onset and rate of development of early blight.