Black Scurf
The affected tubers appear shabby with black mass sticking on the tubers which leads to lower economic return. Normally yield losses to the extent of 25% in the hills and 10% in the plains have been reported.
The emerging sprouts when infected develop cankers causing girdling of the stem bases. The affected plants show upward rolling of leaves with pinkish or purplish margin.
The roots and emerging stolons also get infected having rottage of cortical tissues. Therefore infected plants have poor root system and infected stolons give rise to deformed tubers.
The tubers from infected plants show dark brown to black irregular lumps sticking on the surface of tubers.
Tubers may also show skin cracks, crater like depressions, pitting, stem end necrosis and shape deformity.