Cottage Q&A
QUESTIONOn opening weekend this year, we arrived at our cottage on Gloucester Pool, near Port Severn, Ont., to find that our previously healthy mature hemlock tree had been stripped of most of its bark. Last fall, the tree was alive and well, and now it seems to be dead. Do you know what could have happened?
ANSWER
Like all conifers, when a hemlock goes it usually goes fast, says arborist Steve Mann of Bartlett Tree Experts in Bracebridge, Ont. By the time tree owners become aware of the symptoms and call him in, there's often not much he can do. In almost every case, there's not one single cause, but a combination of factors. For a start, there's your location, Port Severn, a tough habitat for hemlocks because of its shallow soil. Hemlocks like their feet wet, adds John McLaughlin, a forest research pathologist with the Ministry of Natural Resources' Ontario Forest Research Institute in Sault Ste. Marie. So drought, which cottage country has seen a lot of in recent years, is a major enemy. McLaughlin also notes that your photos show heavy foot traffic around this tree, which can injure the roots and compact the already shallow soil.
Once a tree is under severe stress, disease pathogens and opportunistic insects aren't far behind. Bark-boring beetles, such as the hemlock borer, will target a tree in a vulnerable state, sensing the chemical changes in its tissues caused by drought. It's probably these borers that have caused your tree's bark to slough off, speculates McLaughlin. They excavate reproduction galleries for their larvae under the bark of a weakened or dying tree, killing and effectively detaching it from the trunk. Then woodpeckers, in going after the larvae, complete the job. On close inspection, you may be able to see a network of runnels - signs of the borers' hatching galleries - in the bare patches on the tree.
-* Published in the July/August 2003 issue of Cottage Life
