Disease Note.

First Report of Verticillium Wilt of Agastache rugosa Caused by V. dahliae. C. C. Block, North Central Regional Plant Introduction Station, Ames, IA 50011. N. P. Senechal, and M. P. Widrlechner, North Central Regional Plant Introduction Station, Ames, IA 50011. Plant Dis. 73:1020. Accepted for publication 3 August 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-1020E.

Agastache rugosa (Fisch. & C. A. May) O. Kuntze is one of many perennial Lamiaceae (mint) species being studied for potential use in honey production and as sources of essential oils. In May 1986, 58 entries of perennial mints, started from seed, were transplanted to a field in Ames, Iowa. In late May 1981, 25-50% of the plants in two entries of A. rugosa began wilting and dying rapidly. Symptoms also included interveinal yellowing of the lower leaves and internal vascular browning extending several centimeters above the soil line. Yerticillium dahliae Kleb. and Fusarium oxysporum Schlecht. were isolated from stems of symptomatic plants. Each was suspected as a causal agent, especially V. dahliae, which causes Verticillium wilt of peppermint (Mentha piperita L.). Disease-free cuttings of A. rugosa were inoculated by cutting bare roots and immersing them in suspensions of V. dahliae or F. oxysporum inoculum at 1 X 10⁵ and 5 X 1010⁵ conidia per milliliter. Control plants were dipped in distilled water. All control plants and plants inoculated with F. oxysporum remained healthy. All plants treated with V. dahliae began wilting and dying within 30 days. V. dahliae was reisolated from stems of the dying plants. This is the first report of Verticillium wilt on any species of Agastache.