Click to enlarge.

Beginner

Scientific Name
Verticillium dahliae

Identification

• Yellow, V-shaped lesions form at the margins of older leaves
  
• As the disease progresses, these lesions will enlarge and occupy a good proportion of the leaf surface, while still maintaining their characteristic V-shape
  
• The vascular tissue of infected plants becomes brown and discoloured causing the plant to wilt and eventually die

Often Confused With
Bacterial wilt
Gummy stem blight

Period of Activity
Verticillium wilt is present all season. Symptoms are often more severe after fruit set or during dry soil conditions.  The presence of plant parasitic nematodes may further aggravate this disease.

Scouting Notes
While scouting for other diseases, take note of any Verticillium infected plants.  Record the scope and location of any infected areas. Infections frequently occur in patches or in fields with a long history of cucurbits or solanaceous crops (peppers, tomatoes, eggplant and potatoes).

Thresholds
None established.

Advanced

Scientific Name
Verticillium dahliae

Identification
Yellow, V-shaped lesions form at the margins of older leaves.  As the disease progresses, these lesions will enlarge and occupy a good proportion of the leaf surface, maintaining their characteristic V-shape.

The vascular tissue of infected plants becomes brown and discoloured, causing the plant to wilt and eventually die.

Often Confused With
Bacterial wilt
Gummy stem blight

Biology
Verticillium overwinters as mycelium in plant debris and on perennial plants.  It can persist in the soil as micro-sclerotia for long periods of time.  Other host crops and weeds include: strawberries, tomatoes, peppers, eggplant, potatoes and nightshade.

Verticillium is most aggressive at temperatures of 25- 26°C (77- 79°F), although infections may occur early in the season under cooler conditions.  Verticillium often becomes apparent after fruit set or during prolonged dry conditions.

Verticillium enters the plant through the roots.  It plugs the vascular tissue, preventing the uptake of water and nutrients, eventually causing the plant to wilt and die. 

Inoculum levels build up and problems occur when susceptible hosts are planted repeatedly on the same land.

Period of Activity
Verticillium wilt is present all season. Symptoms are often more severe after fruit set or during dry soil conditions. The presence of plant parasitic nematodes may further aggravate this disease.

Scouting Notes
Soils may be tested for Verticillium levels prior to planting.  While scouting for other diseases, take note of any Verticillium infected plants.  Record the scope and location of any infected areas.  Infections frequently occur in patches or in fields with a long history of cucurbits or solanaceous crops (peppers, tomatoes, eggplant and potatoes).

Thresholds
Threshold values have been developed for the solanaceous crops (potatoes, tomatoes, eggplant and peppers).  These thresholds have not been evaluated for other susceptible crops.

Management Notes

• Practice a 3–4-year crop rotation away from susceptible crops (cucurbits, solanaceous crops, strawberries).