First Report of Powdery Mildew on Dipsacus sylvestris Caused by Sphaerotheca dipsacearum in North America

Common teasel (Dipsacus sylvestris) is a European species introduced into North America, and is now widely established and regarded as a noxious weed. In October 2005, a powdery mildew was observed on D. sylvestris in two locations in Pullman, Whitman Co., WA. Examination of diseased material confirmed that the causal agent was S. dipsacearum. This report provides the first documentation of S. dipsacearum on D. sylvestris in North America. Accepted for publication 20 April 2006. Published 7 June 2006.

Leptosphaeria rubicunda. [Descriptions of Fungi and Bacteria].

A description is provided for Leptosphaeria rubicunda. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry stems of its hosts, which are mainly herbaceous, it is not known to cause any pathological symptoms. HOSTS: Apiaceae indet., Dipsacus sylvestris, Leonurus, Lythrum salicaria and Sambucus nigra. GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: Canada (Ontario), USA (New York). EUROPE: Czech Republic, Germany, Great Britain, Hungary, Italy. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

THE BIOLOGY OF CANADIAN WEEDS: 12. Dipsacus sylvestris Huds.

Dipsacus sylvestris Huds., wild teasel, is an introduced weed of pastures, abandoned fields and roadsides occurring in widely-spaced but very dense patches in southern Ontario, Quebec, northeastern U.S.A., and northwestern U.S.A. Original research and information from other studies are incorporated into a summary of the biology of this fugitive plant species.