On older, more robust plants, these points of infection are usually oval or irregular in shape, eventually forming dark concentric rings like those found on the leaves. On seedlings, these infections can circle the stem (“collar rot”), causing the seedling to wither and die. Eventually, the disease spreads to the stems, where it causes brown, sunken spots. In potatoes, early blight also causes extensive premature defoliation.Īs the disease progresses, spots appear on younger leaves increasingly higher up the plant. Dead leaves may remain attached to the plant, or drop to the ground where they can serve as a vector for the disease. Eventually, infected leaves turn yellow, develop fissures, and die. (Image source: Clemson University – USDA Cooperative Extension Slide Series,, licensed via CC BY 3.0 US)Īs spots grow, more spots form nearby. This ridging produces the well-known ‘bullseye’ spots associated with early blight. Note the ridging of the spot near the center of the image. A tomato leaf showing the initial symptoms of early blight. These spots may be surrounded by yellow leaf tissue. Over time, increasingly large rings of tissue around the lesions turn brown or black, forming a ridged spot often described as resembling a bullseye, but which can also be characterized as looking like tree rings. Spots don’t form all at once, instead starting as small pinpoint lesions near leaf centers. The first symptoms of early blight usually appear on the oldest, lowest leaves. Early blight is easily identified by its bullseye-patterned spots, as well as the general pervasiveness of symptoms throughout infected plants. The disease is usually caused by the fungus Alternaria solani, though the closely related Alternaria tomatophila is a common cause of early blight in tomatoes.Įarly blight can be a devastating disease, as it affects every part of the plant, including the leaves, stem, and fruit, causing spots and wilting, and often resulting in leaves and fruit dropping off prematurely. Early blight is a disease which infects tomatoes and potatoes, as well as other crops including okra and eggplant.
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