Small dark sclerotia are formed on desiccated stems and roots. Damage A considerable decrease in yield, but without damage to visual quality. Seed tubers carry the pathogen in their vascular bundles and can transmit the disease. The fungus penetrates through plant roots, becomes established in the vascular bundles, and spreads systemically. The disease is most severe during autumn-winter.
Tolerant varieties exist.
Treatment with low dosages of nematicides can also be partially effective.