Purple blotch

Alternaria porri

Description

The initial symptoms of purple blotch are small, water-soaked lesions with white centers that appear usually on older leaves. As the disease progresses, the lesions enlarge (individual lesions can be as long as 1–2 inches) and become purplish with light yellow concentric rings on the margins. As severity increases, leaves turn yellow brown, lose erectness, and wilt. Windborne conidia from previous crop debris intiate infection, which is favored by high temperatures and humid conditions. Prolonged leaf wetness increases the probability of further infection.

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