Tomato Blights Wet spring and early summer conditions have favored the development of fungal blights of tomato. Two common foliage diseases of tomato are early blight, caused by Alternaria solani, and Septoria blight, caused by Septoria lycopersici. Lower leaves are usually attacked first. Septoria causes smaller brown spots that eventually turn light tan or gray in the center with a dark border. Both diseases cause foliage to eventually turn brown and die.
Cultural practices can help reduce disease outbreaks.
This acts as a barrier against the introduction of fungal spores from the soil. Space plants adequately to allow good air circulation. Since these fungi can overwinter on infected leaves, it is also important to remove plant debris at the end of the season. Rotate away from tomatoes and potatoes for several years. Fungicide sprays, such as Daconil 2787, may be needed.