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.
For more information about this plant pest, see the CABI data sheet.