Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001682
11/12/99
Dutch Elm Disease
Dutch elm disease is a vascular wilt that killed nearly
all American elm trees in the United States, except where
susceptible trees were isolated far from others of their
kind. American elms as street trees exist today only in
municipalities that have a monitoring and control program.
The Siberian and Chinese elms and the hybrid elms are
resistant to the disease.
Symptoms: Wilting, yellowing foliage and leaf drop first
occur on one or a few branches. Then the entire tree may
wilt and die in a few months to a few years.
Cause: Bark beetles that feed in the branch crotches of
elm trees and burrow tunnels and lay eggs in dying or dead
elm wood carry the fungus that causes the vascular wilt
disease. Beetles generally are attracted to stressed
trees rather than healthy trees. Controlling the beetles
may help control the disease. Quickly destroying dead elm
wood and dying trees and keeping healthy trees vigorous
helps to limit the spread of the disease.
Control: Prune out infected branches immediately. When
pruning, cut well below the area showing symptoms -- at
least 6 feet below the brown vascular discoloration on
the wilted branch. The pathogen usually is a distance
beyond the symptoms. Systemic insecticides and fungicides
have not been proven fully effective. A number of resistant
elms have been developed and these should be considered if
an elm is desired.
Closely planted trees should be treated to remove the chance
of root grafting. This is best done by passing a root
cutting blade, 2 feet deep, midpoint between the trees.
This severs root connections between trees. Alternatively,
a soil fumigant can be placed at an appropriate
concentration in holes 2 feet deep and 8 inches apart, along
the midpoint between two trees to kill intermingling roots.
Fumigants must be applied by a licensed professional
pesticide applicator.
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to commercial products or trade names does not imply
endorsement by MSU Extension or bias against those not
mentioned. This information becomes public property upon
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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