How to Manage Pests

Pests in Gardens and Landscapes

Black mold—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.

Solutions

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.

Watery rot of black mold on onion
Watery rot of black mold on onion

Black mold fungus between scales of bulbBlack mold fungus between scales of bulb


Statewide IPM Program, Agriculture and Natural Resources, University of California
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