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Verticillium Wilt

by Elizabeth H. Roche, Nancy J. Taylor & Francesca Peduto Hand

Identification

Verticillium enters and colonizes the roots of host plants invading the xylem tissue. As a result of the fungus activity and the plant’s reaction to the invasion, the vascular system clogs preventing water and nutrients from moving throughout the plant. As a consequence, symptoms of the disease are characteristic of a non-properly functioning vascular system, including:

• Stunting
• Wilting
• Leaf chlorosis
• Leaf scorch
• Defoliation
• Brown-black discoloration (streaking) of xylem tissue may be present (visible in longitudinal or cross-sections). Since this is almost identical to that caused by Fusarium wilt, a confirmatory laboratory diagnosis is recommended.

Microscopic observation of infected tissues may reveal the presence of tiny black structures (microsclerotia).

For assistance in identification, contact the C. Wayne Ellett Plant and Pest Diagnostic Clinic.

Management Guidelines

• Use resistant cultivars whenever possible.
• Use culture-indexed pathogen-free plants.
• Check incoming plant material for symptoms before introducing them into production.
• Remove and destroy any symptomatic plant.
• Control insect pest populations.
• Adopt proper soil sanitation practices. Always use clean soil. Soil can be disinfested by steam (140°F for 30 min), solarization (double tent at 160°F for 30 min or 140°F for 1 hour), or chemical treatment (fumigation).
• For field production of cut flowers, avoid fields that have previously hosted susceptible crops.
• Fungicides are generally not effective for disease control.