Apparently in Southern Ontario, possibly elsewhere hemlocks are declining showing no external symptoms of insect or disease. Samples have also been taken to a local pest diagnostic clinic finding no pathogens. Some comments that I have been hearing is stress related to atmospheric changes.These are typically urban trees. (e.g. planted or in remnant woodlot areas. Has anyone else heard of or investigated this?

Reply to post by Jack Radecki, on April 14, 2000 at 16:31:56:

Out on the west coast the western hemlock (Tsuga heterophylla)is very shallow rooted, and as a result, intolerant of prolonged drought. It is quite common to see clumps of regen dying in the season following a very dry summer, or to see semi mature and mature trees dead due to drought stress. One year the tree seems fine, the next season, it flushes and promptly sheds all the foliage and then -- toast. An alarming phenomenon to the unitiated

Julian

Reply to post by Julian Dunster, on April 14, 2000 at 16:31:56:

Drought stress makes sense to me. As we all know the last 2 years for the eastern provinces and the north-east states have been extremely dry. As I am following up for other arborists in the area, I would still like to do my own observations. For example, hemlocks north of Toronto at or near my cottage (Peterborough area) seem to be fine.