Joseph O'Brien, USDA Forest Service,

Dutch elm disease

Ophiostoma ulmi

Dutch elm disease (Ophiostoma ulmi) is a fungal pathogen of Elms especially the American Elm . It is a native of the Orient and was first detected in Ohio in 1930.

Streaking below the bark and flagging, or wilting and yellowing of the leaves on a branch of the tree, are common symptoms of the disease which has decimated over half of the American Elms in this country.