Purple blotch

Symptom

Older leaves tend to be more susceptible than younger leaves. Symptoms begin as water-soaked lesions that usually have a white center. Under humid weather conditions, the disease intensifies, producing brownish oval lesions with purple centers on the leaves, often forming concentric rings. These lesions are surrounded by yellow halos, and as they enlarge, they can encircle the entire leaf, causing it to wither and collapse. As foliage declines, photosynthesis is reduced, leading to lower bulb yields. In onion grown for green shoots, this disease reduces the number of marketable leeks.