• Black smut sori are seen at the base of the leaves and leaf surface.
• Black powdery mass is seen after rupturing of sorus wall.

• The sori of urocystis cepulae contain dark coloured and powdery spore masses. The spores are found in permentant balls. Each ball consists of an enveloping cortex of tined, sterile, bladder like cells with one or two central dark coloured thick walled chlamydospores. The spores germinate by means of short promycelium while still in the ball.

Management:

• Seed treatment with Thiram or Captan @ 4g/kg.
• The bulbs may be dipped in Thiram solution 0.25%.

Source:

Images: http://mtvernon.wsu.edu/path_team/onion.htm,
Microscopic image: http://www.discoverlife.org/mp/20q?search=Urocystis+anemones