Disease Note

Verticillium Wilt of Dusty-Miller (Senecio cineraria) Caused by Verticillium dahliae. S. T. Koike, University of California Cooperative Extension, Salinas 93901. Plant Dis. 75:319. Accepted for publication 13 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0319F.

In 1988 in Santa Barbara County, California, commercial plantings of dusty-miller (Senecio cineraria DC. 'Silverdust') being grown for seed prod uction showed symptoms of a wilt disease. Plants were severely stunted. Terminal shoots wilted , foliage faded to a whitish hue, and plants dried up and died . Stem xylem tissue often was dark red to brown. Isolations from stem tissue consistently yielded a fungus having verticillate conidiophores and black microsclerotia. The fungus was identified as Verticillium dahliae Kleb. Pathogenicity was tested by dipping roots of 8-wk-old seedlings, grown in plug trays, into an aqueous suspension of conidia produced on potato-dextrose agar. The suspension was adjusted to 1 X 10⁵ conidia per milliliter. Seedlings were repotted into a pasteurized potting mix and kept in a greenhouse at 20- 25 C. Control plants were dipped into sterile distilled water and then handled in the same way as inoculated plants. After 3 mo, the inoculated plants showed wilting and shoot die back, whereas control plants remained unaffected. V. dahliae was reisolated from the inoculated plants. This is the first report of Verticillium wilt on S. cineraria. This new finding is significant because flower seed crops such as S. cineraria are often rotated between vegetable crops that are susceptible to Verticillium wilt, such as cauliflower, Chinese cabbage, tomato, and artichokes grown as annuals.