The Wisconsin Department of Natural Resources wants landowners to be aware of an invasive species discovered in Michigan.
Hemlock woolly adelgid attacks hemlock and fir trees. The pests are invasive, sucking, aphid-like insects that kill trees. They are too small to see with the naked eye, yet the harm is apparent.
The pests’ white, cottony egg sacs can be found year-round on the undersides of hemlock branches near the base of the needles. The adelgid’s saliva penetrates the tree while the insect feeds; it is poisonous and causes needle drop and twig dieback, which leads to tree death in 4-10 years.
In Wisconsin, balsam and Fraser fir are particularly vulnerable. When an insect injects poisonous compounds during feeding, the terminal branches will stunt and bulge (gouting). Adult adelgid feeding causes needle discolouration and loss, and can kill trees in as little as two years.