Dutch elm disease in Illinois dutchelmdiseasei53cart Year: 1967 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 brown discoloration (Fig. 3, 4, and 5) described above. In dying and dead trees invaded by bark beetles, the fungus grows in the galleries made by the larvae or grubs of the beetles (Fig. 6). These galleries are in the inner layers of bark with groovings on the outer surface of the sap wood. Fig. 4.—The removal of bark from branches that wilt in early summer usually reveals long, broken, brown streaks on the surface of the sap- wood.

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