How to Manage Pests

Pests in Gardens and Landscapes

Common scab—Streptomyces spp.

Common scab lesions are usually circular and 6 - 8 mm in diameter, but they can be smaller in early stages of development and larger if they coalesce. Lesions typically possess a raised margin and slightly depressed center. Scab may appear on tubers as superficial tan to brown corky lesions or beneath the tuber surface as lesions with depressions. Lesions may also be cushionlike or warty.

Solutions

Common scab is largely cosmetic; affected tubers are edible. Many varieties are resistant. If scab occurs, change varieties in the next year. The disease is favored by neutral to basic soil; sulfur may be worked into the soil to make it slightly acidic and thus reduce disease.

 

 

Superficial corky lesions of common scab
Superficial corky lesions of common scab

Depressions beneath tuber surface
Depressions beneath tuber surface

 


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