Signs and Symptoms of Dutch Elm Disease
Dutch elm disease is a vascular wilt caused by the fungus Ophiostoma novo-ulmi. The fungus stops the movement of water through the tree.
The fungus can infect most species of elm (Ulmus spp) and is often is carried from tree to tree by the elm bark beetle Scolytus multistriatus which feeds and breeds on elms.
The first sign that a tree is infected by the disease is curling and ‘flagging’ of leaves, often on an individual branch or on a collection of branches in one part of the tree’s crown. The leaves then turn brown and most branches die.
This dieback can occur rapidly (within a few weeks) or gradually.
When a branch is cut, a brown circle or ring of dots is often visible. This discolouration in the branch is a major diagnostic tool for surveyors, when identifying the disease.
Samples of suspected infected wood can also be sent to a laboratory for confirmation of Dutch elm disease.