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Early blight Photo Identification
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  • Pest Type: Disease
  • Crops Affected: Potatoes
  • Scientific Name: Alternaria solani
Symptoms
Early blight affects leaves, stems, and tubers. Lesions first appear as pinhead-sized dots on older leaves. The lesions expand and develop concentric rings of dead tissue that may give a target appearance. A yellowish "halo" may develop around the lesions. Lesions may eventually spread to the stems. Tuber lesions are dark, sunken, and irregular shaped. Heavy foliar infections cause yield reductions.

Disease Cycle
This fungus survives mainly on crop residue, but also in soil, in tubers, and on other plants in the solanaceae family. Airborne spores released from these sources and from leaf lesions spread the disease, usually starting about flowering time. Early blight is usually more severe when the plants are under stress during alternating wet (dew) and dry periods. Early blight tuber blemish enters the tuber through cuts and bruises.

Control Measures
Begin monitoring potato crops at the beginning of flowering. When most of the lower leaves contain spots/lesions, begin fungicide applications. To further reduce early blight tuber blemish, allow at least 4 days between vine kill and digging, for the tubers to harden-off. Avoid tuber injury during harvest and practice good sanitation.
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