Alternaria solani, the pathogen that causes early blight in potatoes, infects plants either through leaves, which is more common in the eastern U.S., or through tubers, which occurs more often in the western part of the country. Able to overwinter and move to different fields, this disease is good at surviving and bad for crop yield.

Symptoms of early blight don’t always manifest right away and are easily overlooked. Noticeable signs of foliar infection are small, circular, dark-brown or black rings that first appear on older, lower leaves. Michigan State University notes that these lesions can merge as they grow, leading to misinterpretation of the lesions as symptoms of late blight. The main difference between lesions amongst the 2 diseases is that early blight lesions tend to have concentric rings. Left untreated, early blight progresses into the plant’s upper leaves, causing them to wither and die.

Signs of tuber infection include irregular, slightly sunken lesions that are usually surrounded by raised purple to dark brown coloring. In addition, the potato tissue takes on a leathery or corky texture, with a dry, dark brown appearance. Tuber symptoms can appear after months of storage, making it difficult to recover potatoes once they have been infected and resulting in a loss of marketable potatoes.

The most effective way to combat early blight is a foliar fungicide. Kiran Shetty, Ph.D., technical development lead for Syngenta, explains the results of a trial on early blight control. Shetty recommends Miravis^® Prime fungicide to control early blight and other common potato diseases.

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