Dothistroma Needle Blight, Caused by Dothistroma septospora, of Pinus spp. in Vermont.

Abstract

Dothistroma needle blight, caused by Dothistroma septospora (teleo-morph Mycosphaerella pini), is a serious foliage disease of pine species throughout the world. In the northeastern United States, the fungus has been reported from Pennsylvania, but not New York, New Jersey, or any of the New England states. It has been reported from the eastern provinces of Canada (Newfoundland, Quebec). During 1994 to 1998, stromatic conidomata consistent with descriptions of D. septospora were associated with needle blight symptoms on mature landscape pines at four locations (Jericho, Montpelier, Williamstown, Williston) and one Christmas tree farm (Barre) in Vermont. Pinus nigra was affected at four locations; P. mugo and P. ponderosa were affected at one location each. Severe foliar blight and defoliation occurred during successive years on P. nigra and P. mugo. Collections from each location and host were examined microscopically. Mean lengths and widths of 20 or more conidia from each of three collections of P. nigra (Barre, Montpelier, and Williston) were 2.3 × 25, 2.7 × 20, and 2.6 × 24 μm, respectively. Corresponding values for collections from P. mugo and P. ponderosa were 2.4 × 26 and 3.6 × 31 μm, respectively. All collections conformed to descriptions and illustrations of D. septospora (1). No ascigerous state was observed from 1994 to 1998. This is the first report of D. septospora in New England. Reference: (1) H. C. Evans. 1984. The Genus Mycosphaerella and Its Anamorphs Cercoseptoria, Dothistroma and Lecanosticta on Pines. Commonwealth Mycological Institute, Kew, England.