Abstract

Cuthbert, R. A., W. N. Cannon. Jr., and J. W. Peacock. 1975. Relative importance of root grafts and bark beetles to the spread of Dutch elm disease. USDA Forest Service Research Note NE-206. 4 p.

Root-graft transmission of Dutch elm disease (DED) is sometimes ignored in both research studies and city programs to control DED. We conducted studies in Detroit, Michigan to (1) distinguish between root-graft and beetle-transmitted cases of Dutch elm disease, and (2) determine the relative importance of both kinds of disease transmission. Our results indicate that elms adjacent to 1-, 2-, or 3-year-old stumps have a disease rate three to five times higher than elms not adjacent to stumps. We conclude that in Detroit, which has elm plantings typical of many United States cities, root grafts were probably responsible for more than 50 per cent of the DED transmission in 1973.

• © 1975, International Society of Arboriculture. All rights reserved.