This past summer a 70ft, 27"dbh tree, I believe it is Ulmus thomasii, lost most of its foliage. The leaves dried up over 80% of the crown and dropped in August. Preliminary investigations have not found sign of DED. It was suggested that lack of water may have been a factor. The area is irrigated, no major disturbances within 50ft. Other plants seem unaffected, save a Scotch pine with mites and bark beetle. This Elm, according to Dirr, is found on dry slopes and uplands. I wonder whether others have any ideas?
Reply to post by Kenneth Cote, on December 04, 2000 at 17:55:51:
I recently read that the massive oak blight in California is being caused by a Phytophora fungus which mutated from a Phytophora which attacks NW evergreens (cedar, I think). Could this be another mutation? I'm not too familiar with it (interested in finding out more), but I know that leaf drop/defoliation is a primary indicator of the fungi's presence in the oaks.
Reply to post by Kenneth Cote, on December 04, 2000 at 14:36:10:
Consider mites. I had a case (in Delaware) years ago with yellowing and leaf drop, finally identified as an eriophyid mite, on American elms. The foliage dropped yellow, not dried.
Yellows is a possibility, despite claims it isn't there yet. Light brown streaking under the bark near the base, slight wintergreen odor (place bark chips in plastic bag for a few hours).
