Q. I have a Japanese Red Maple whose leaves on a few branches started to die during the summer of 2005. Most of the tree’s branches are fine, but I am concerned that the problem will spread. Could you please let me know what you think the issue is and how I can solve it? Brian Watson – Spanaway, WA
A. It is hard to determine the exact cause from your description since there are a few conditions that could cause leaf and twig dieback. The simplest cause could be drought. Trees that do not receive supplemental water in the summer and are in a fully exposed site (full sun) can sometimes show dieback leaves and smaller branches. The initial symptoms on the leaves would look like the leaves were scorched. This would be an environmental condition. But this condition could then lead to a fungal infection (if the fungal spores are present). If you saw leaf spotting on the leaves before they died and then you had twig dieback it could be a bacterial disease – especially if the dieback occurred in the late winter early spring. It could also be a soil borne disease called verticillium wilt. In this case the leaves would droop and turned yellow to brown. In any case you should prune back to living wood to remove the dead areas – preferably to a bud. Disinfect your pruners between cuts so you don’t move the disease around and remove the clippings from the garden. If you are seeing discoloration in the cut stems (in the living tissue) then you could have verticillium wilt. Also clean up any leaf debris and replace fresh mulch as a precaution.