How to Manage Pests

Pests in Gardens and Landscapes

Seasonal development and life cycle—Powdery scab

The fungus that causes powdery scab survives in the soil as resting spores, which form the spore balls released from tuber and root lesions. Stimulated by the presence of susceptible host roots, resting spores germinate to produce mobile spores that swim through soil water to infect roots or stolons. These infections produce additional spores that spread infection to roots and tubers.

Resting spores survive in the soil for up to 6 years and can survive passage through the digestive tract of animals. The fungus can also infect and produce resting spores on the roots of other potato family plants such as tomato and nightshades. Powdery scab is favored by cool, moist conditions, and symptoms are most severe on white- and red-skinned tubers.

Powdery scab infection
Powdery scab infection

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