Symptoms and signs of white mold on an onion plant cut lengthwise   through the bulb to reveal a rot extending into the bulb, and dark, pinhead size sclerotia of the pathogen, <em>Sclerotium cepivorum</em>.

Symptoms and signs of white mold on an onion plant cut lengthwise through the bulb to reveal a rot extending into the bulb, and dark, pinhead size sclerotia of the pathogen, Sclerotium cepivorum.

Photo Source: Lindsey du Toit, Washington State University.