Top: Early summer symptoms (green, wilting leaves) Bottom: mid summer symptoms (clinging, brown, wilted leaves)
The early symptoms of the disease appear from the latter half of June to the middle of July when the leaves on one or more branches may wilt, droop and curl. The leaves then turn brown and usually remain on the tree.
If the tree is infected later in the summer, the leaves will droop, turn yellow (this is called flagging) and drop prematurely. Late season infections are easily confused with normal seasonal changes.
All of these symptoms are accompanied by brown staining in the sapwood that can be seen by removing the bark of infected twigs.
Since other diseases can cause symptoms similar to those of DED, positive identification requires a laboratory test.
Signs of Beetle Activity
Beetle emergence holes, the size of the diameter of a pencil lead, and/or sawdust on the bark, indicate burrowing beetles. The beetles are 3.5 mm (1/8 inch) long. The characteristic pattern of the breeding galleries on the surface of the wood under the bark can also be used to identify the two elm bark beetle species.
Please report any suspected Dutch elm disease problems on private or public elm trees to 311 or firstname.lastname@example.org.