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