Verticillium wilt is more insidious than fusarium wilt because its host range is broader, it operates in cooler soils, and the symptoms can take weeks to develop, giving the impression that the plant will recover when it will not. The disease is caused by two closely related soil-borne fungi: Verticillium dahliae and Verticillium albo-atrum.
Per UC IPM, verticillium wilt is one of the most important soil-borne plant diseases worldwide, affecting several hundred plant species across nearly all plant families. In the home garden, vegetable crops and strawberries are most commonly affected. In the landscape, it is a significant problem on maples, elms, roses, and many ornamental shrubs.
The pathogen and how it works
Verticillium dahliae and Verticillium albo-atrum are soil-borne ascomycete fungi. Per UC IPM, both species produce microsclerotia (tiny resting structures) that survive in soil for extended periods — research has documented V. dahliae microsclerotia remaining viable for 10 to 15 years or more.
The infection pathway: per Missouri Botanical Garden, the fungus enters through roots — particularly wounded roots — and colonizes the water-conducting xylem tissue. Wilting results from clogging of xylem vessels with fungal material and plant defensive responses to infection.
Per NC State Extension, the disease is favored by cool to moderate soil temperatures of 65°F to 75°F (18°C to 24°C), which distinguishes it from fusarium wilt (most active at 80–90°F). On Long Island, early summer conditions before soil temperatures peak are verticillium season for vegetable crops. In cooler regions it may be active throughout the summer.
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