Causal Agent

The fungus Ophiostoma ulmi 

 

Hosts

Native American Elm and other varieties. 

 

Symptoms

The first evidence of DED is a wilting or "flagging" in one or more of the upper branches. Leaves on affected branches turn dull green to yellow and curl, then become dry, brittle and turn brown. Some trees die several weeks after becoming infected, while others wilt slowly and survive for a year or more. Peeling the bark from wilted branches reveals light to dark brown streaks or blue to gray discoloration of the wood beneath the bark. In cross section, this vascular discoloration appears as a brown ring in the outer sapwood of the wilting and dying branches. To positively identify DED, specimens from actively wilting branches with definite vascular discoloration are needed (the fungus cannot be isolated from dead, dried branches). Samples should be sent to your local diagnostic lab for diagnosis. 

 

Control

Early infections can be removed from elm trees by pruning. A minimum of 8-10 feet of streak-free wood (no vascular discoloration) below obviously infected branches must be removed. The entire circumference of the branch must be examined to be certain that the fungus has been removed. These trees should be examined regularly for any further development of the disease. Please contact your local county extension office for current information.