I have a potential customer who has 58 mature hemlocks with active wooly adelgid. The average D.B.H. is 22", heights are about 40-50 ft. Spraying is out of the question, they are close to a pond and a stream. I'm considering merit soil injections but I'm wondering if any of you have experience using the trunk injectors and which would be more cost effective? Any help would be appreciated.