How do you treat Hemlocks with an infestation of Woolly Adelgid?

August 17, 2022 Ask the Expert, Managing Insect, Diseases, and Animal Pests

Question:

How do you treat Hemlocks with an infestation of Woolly Adelgid? These hemlocks are within 50 feet of two drilled wells.

Answer:

Donna R. Coffin, Extension Professor

First you need to be sure you are dealing with the Hemlock Woolly Adelgid. There are some look alikes.

Once you are sure you have HWA if you haven’t already, you will want to report it to the state forest service. This is important since they are deploying biological controls.

The two best options for homeowners to treat are dormant oil or insecticidal soap. There is a caution, not to spray drought stressed trees, so you may need to wait until your area gets more rain.

Here is the Maine Forest Service factsheet on Hemlock Woolly Adelgid.