Onion smut

Plants with symptoms of the onion smut disease. Image: Howard F. Schwartz, Colorado State University, Bugwood.org

  • Onion smut affects onions, spring onions, leeks and garlic.
  • Damages the whole plant.
  • Occurs as distinctive narrow long dark streaks, usually on the cotyledon or first true leaf, which become thickened. The streaks are evidence of an infection that initially affects the inside of the leaf and later bursts through the leaf surface and releases masses of dark-brown powdery spores.
  • Onion seedlings usually die within a few weeks and plant populations are reduced. Diseased plants that survive are often distorted, develop blisters on green leaves and remain stunted. Yields are reduced. Mature bulbs may, less commonly, have dark pustules.
  • Spread through seedlings, soil and bulbs.

High priority pest of: Onions

Scientific name: Urocystis cepulae
EPPRD Category:
Life Form: Fungus

Pest Documents

FS: fact sheet

CP: contingency plan

DP: diagnostic protocol