An infected elm tree usually exhibits symptoms soon after infection. Because of the speed with which the disease attacks, detecting symptoms as early as possible is essential for treatment.
The first sign of the disease is the sudden wilting of leaves in the upper reaches of the tree
Next, the leaves change colour from green to yellow to brown. They then shrivel and die.
If the infection occurs very late in the season, the leaves will appear to fall normally. However, the following spring the new leaves will be smaller than normal. The tree will often die
In late summer, it may be difficult to distinguish between wilting and natural fall colours.
Discolouration of the wood is also a sign of the disease. If you peel back the bark on a wilted branch, you will see some streaking on the wood.