Dan Egel, Extension Vegetable Pathologist, Purdue University
Some potato growers may be disappointed with this year’s crop. Common scab of potato has been observed in Indiana this summer. This disease causes the surface of potatoes to become russeted, raised, corky or pitted. It isn’t possible to tell whether a potato has common scab from the above ground parts of the plant.
Scab of potato is caused by a bacterium that is both common and survives well in soil. The pathogen can spread with water, infected tubers or farm/garden equipment.
Common scab of potato can be controlled by keeping the soil moist during tuberization, practicing crop rotation and using potato varieties that have partial resistance to common scab. It isn’t possible to control scab by applying any pesticide to the potatoes. More information about the control of common scab of potato can be found in the Midwest Vegetable Production Guide for Commercial Growers 2012.
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Figure 1: The recent dry weather may have contributed to the disease common scab of potato which may cause a corky appearance to the surface of potatoes as shown here.