Diseases of pepper (
Verticillium wilt
Verticillium wilt is caused by the fungus Verticillium dahliae. Disease usually shows up late in the season on mature plants (photo 1). Diseased plants wilt and usually die (photo 2). Unlike Phytophthora root rot which causes a similar wilt, the roots are not rotted. V. dahliae is a soilborne fungus that invades the plant through the root, and grows into the vascular system causing a reduction in water flow through the plant. It has a wide host range, and is able to survive in the soil for long periods of time as structures called microsclerotia. The microsclerotia are produced in the plant tissue, and can survive and be spread in plant debris.
Substances produced in the plant during infection may also result in discoloration of the vascular tissue. Brown streaks or flecks often can be observed in cut stems and are diagnostic of the disease, but are not always present.
There is no control for Verticillium wilt and to date resistant cultivars are not available. Avoidance of known infested fields and rotations of several years are recommended, although the microsclerotia of the fungus are known to survive for many years. Rotation to small grains and alfalfa, which are not hosts, may result in reduction of disease. Cotton rotations should be avoided since cotton is very susceptible to some strains of V. dahliae.
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February 24, 2003