Hemlock borer requires a stressed or weakened host. The two major causes of stress for hemlock are defoliation and drought. Susceptibility to drought results from the fact that this conifer is very shallow-rooted and typically does best on moist-to-wet sites. The species is so sensitive to changes in soil moisture conditions that merely opening up a stand of hemlock too much or removing associated hardwoods in mixed stands and leaving the hemlock is often enough to set the stage for hemlock borer.
Read more about plant health care recommendations for hemlock and schedule an appointment with a Bartlett arborist if you’ve noticed the pest or the symptoms on hemlocks on your property, or to make your trees less susceptible to the hemlock borer.