How to Manage Pests
Pests in Gardens and Landscapes
Black mold on onions and garlic—Aspergillus niger
Black mold is first evident at the top or sides of onion or garlic bulbs where disease or injury has
caused an opening in the skin. The fungus develops between dry, dead outer scales and the first inner
fleshy scales of the bulb. Invaded scales become water soaked and may dry and shrivel and develop black
masses of spores. The whole bulb may eventually deteriorate into a watery soft rot.
Handle bulbs to avoid bruising and reduce injury and invasion sites for the fungus. Storing at temperatures between 33 and 55°F will help suppress black mold development, as it occurs mostly under warm, dry conditions. There are no chemicals for the direct control of black mold.
rot of black mold on onion
mold fungus between scales of bulb