Verticillium Wilt

Symptoms often begin as wilting or marginal chlorosis and necrosis on one side of the plant or on lower leaves, progressing upward as the disease develops. A cut stem typically shows brown to dark vascular discoloration corresponding to the colonised xylem tissue.

The fungus survives in soil as microsclerotia for a number of years, even in the absence of a host. When a susceptible root grows nearby, the fungus germinates and penetrates the root, then colonises the xylem, where it restricts water movement and triggers the plant's wilting response.

• Microsclerotia can persist in soil and infested crop debris for extended periods
• Spread within a field occurs via infested soil, irrigation or surface water, and contaminated equipment
• Symptom severity is often worsened by additional plant stress, such as drought

Verticillium wilt affects a very wide range of woody and herbaceous crops. Cotton, eggplant, olive, and potato are notable hosts, and a history of any susceptible crop in rotation can raise soil inoculum levels affecting others.

• A field history of susceptible hosts, building soil microsclerotia levels over time
• Cooler soil temperatures during crop establishment
• Drought or other plant stress, which can worsen wilt symptoms
• Movement of infested soil or plant debris on equipment between fields

Because the fungus persists in soil for years, prevention relies mainly on reducing inoculum build-up over time and minimising additional plant stress rather than in-season intervention.

• Use long rotations with non-host or resistant crops where the disease history is known
• Choose resistant varieties or rootstocks where available
• Sanitise equipment moving between infested and clean fields
• Maintain adequate, consistent irrigation to reduce additional drought stress on the crop