A New Species of Dothiorella Causing Die-Back of Elm

Abstract

Dothiorella Ulmi is the pycnidial form of the fungus previously reported as causing the disease commonly known as the Cephalosporium die-back of elm. This disease was observed on American elm (Ulmus americana L.) in Minnesota in 1929 and the causal organism tentatively placed in the Sphaeropsidales because of pycnidia formed on malt agar (5). The same organism was isolated from specimens collected in 1930 in the midwestern and eastern states and reported as Cephalosporium sp. (3). The fungus has also been reported from Nebraska (2). The disease of American elm noted from Connecticut in 1930 (1) has subsequently been found by a comparison of cultures to be caused by the same organism. The Cephalosporium stage of the fungus was isolated from diseased elms. Transfers were made from these cultures to sterilized