Two common foliage diseases of tomato are early blight, caused by Alternaria solani, and Septoria blight, caused by Septoria lycopersici. The overall effect of both blights is similar.
Leaves turn yellow, brown, then wither and die.
Septoria blight and early blight both overwinter on infected debris from previous years. If there are only a few plants in a garden, the progress of the blights may be slowed somewhat by removing infected leaves as they appear. Nevertheless, f ungicide sprays are likely to be needed if these diseases are present. Many products are labeled, including Bravo and Dyrene, and should be applied every week to 10 days through harvest. Cultural techniques can help to reduce the risk of foliar blight outbreaks, but it takes some advanced planning.