Origin:
True to its name this beetle is native to Europe and northern Asia, but it now is found throughout North America wherever elm tree hosts occur.
Biology:
This beetle is another vector of the fungus that causes Dutch Elm Disease, carrying the fungus from an infected tree to a healthy one as the adult beetles exit the infected tree in which they developed. Adult beetles overwinter in cavities at the base of the trees, emerging in late April and May to fly to the branches of trees that already are in dying or weakened condition. The female burrows under the bark, bores a gallery in that area, and deposits eggs along both sides of this channel. The larvae then burrow outward from this egg channel to feed in the cambium of the tree. The fungus then moves through the vascular system of the tree, resulting in sudden wilting of the foliage and death of the tree. There is a single generation of the beetles each year with new adult emerging in July to fly to new trees where they feed on the bark and infect those trees.
Identification:
Adult beetles are only about 3-5 mm long and a dark brown to blackish color. The ventral area at the rear end of the body is concave, with a spine or point present that points backward. The appearance of this species is similar to the Native elm bark beetle, but this species lacks the concave area and spine. The head projects somewhat forward from the prothorax and is visible from above. The antennae are typical of bark beetles with several very small and short segments and a much larger, rounded terminal club.
Characteristicts Important to Control:
Heavily infested trees are removed and burned. Those with only minor evidence of Dutch Elm Disease may be heavily pruned to remove the infected branches immediately after any wilting is noticed. Maintaining trees in a healthy state will help them to repel attacking beetles. Preventive applications of residual insecticides may be applied to the trunk and branches prior to the emergence of the adult beetles in the spring. Systemic insecticides may also be helpful, either as soil applied chemicals that are taken up by the roots or as trunk injections.
