Symptoms may develop on any part of the plant, but are most common on the undersurface of leaves. Small, wartlike bumps form that may coalesce into ridges. Epidermal cells of the wart-like areas may rupture. Leaf blotching may also occur.
Conditions for Disease Development
The disorder generally occurs when the soil is warm and wet, and the air temperature is cool. For example, this may occur on a cool night after several warm, humid days. Prolonged periods of high humidity favor edema.
For greenhouse crops, place heating pipes away from soil beds and close ventilators at night. Manage irrigation to help ensure proper soil moisture.