Verticillium wilt is mainly soil-borne, but can also be carried via seed tubers. The disease is favoured by crop stress induced by heat, drought, nutrient deficiencies and insect damage. Pathogenic fungi build up in the soil with repeated potato production and can survive there for long periods. Fungus is transported by anything that moves soil such as farm machinery, footwear, animals, water and wind. It can also be harbored by other crop species without visible disease symptoms.
The fungus penetrates plants through the roots and spreads upwards in the vascular tissue restricting water uptake and infecting stems, petioles and leaves.