The symptoms usually appear immediately after new leaves emerge in early spring. This fungus blocks the water-conducting vessels within the tree, thus initial symptoms include discoloration and wilting of foliage in affected branches. These leaves turn from dull green to yellow then curl and then turn brown, dry, and brittle. Wilting, shriveling, and browning is observed from late spring until late August or September. Light to dark brown streaks or blue to gray discoloration is observed in the wood immediately beneath the bark.
Sanitation helps prevent the spread of Dutch elm disease.
This includes early detection of the symptoms, disruption of root grafts between the healthy and infected trees, and the removal and disposal of all dying and dead elm trees with intact bark. Debarked logs are o.k. to save, as are chips from DED-infected trees. For the greatest margin of safety, compost the chips in a pile for a few months before using them. Prepared by Carmen Sanogo and Paula Flynn , s, Department of Plant Pathology Iowa State University , Ames, Iowa. This information subject to a usage policy .