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First Report of Nematostoma artemisiae on Artemisia in the United States

A fungus associated with leaf hairs of Silver King also known as Silver Wormwood (Artemisia ludoviciana Nutt. subsp. albula (Wooton) Keck) from Missouri (Crawford County, near Bourbon) was identified as the loculoascomycete Nematostoma artemisiae Syd. and P. Syd. When the fungus is present, the leaf hairs become discolored due to the numerous dark ascocarps and eventually drop off and the living leaves lose their silvery appearance, detracting from the ornamental value of the plants. Undocumented observations suggest that the fungus occurred on this host in Ohio and other states of the Midwest in 1995. N. artemisiae was described from Japan on Artemisia indica Willd. and reported once from China on that host. The type specimen was recently redescribed and illustrated by Sivanesan (1) who provided an account of the genus of which this is the type species. The uniloculate fruiting bodies of N. artemisiae are solitary, superficial to basally immersed, dark brown, globose, 120 to 160 μm in diameter, with four to 10 black setae 125 to 175 (300) μm long extending from the thickened region around the ostiole. The bitunicate, cylindrical, 8-spored asci are 50 to 65 × 7 to 9 μm and contain pale brown, broadly fusiform, smooth ascospores, 14 to 18 × 4.5 to 5.0 μm, three-septate, slightly constricted at each septum. The anamorph pycnidia are similar in appearance to the ascomycete fruiting bodies and contain hyaline, broadly spherical conidia 3 to 5 μm in diameter. The specimen has been deposited at the U.S. National Fungus Collection (BPI 749199).

Reference: (1) A. Sivanesan. Syst. Ascomycetum 6:201, 1987.