Risk factors

The disease is favoured by high temperatures (optimum development temperatures of 22 to 27°C with V. dahliae and 16 to 25°C with V. alboatrum), stressful growing conditions (alternating dry and wet periods), high water salinity and, above all, short rotations.

Penetration by the fungus into the roots may be favoured by the presence of free-living nematodes of the genus Pratylenchus in the soil or co-infection by Pectobacterium bacteria in the seed tuber.