Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001739
11/12/99
Bronze Birch Borer
The damage caused by bronze birch borer is very visible
but the insect is rarely seen.
The insects overwinters as larvae in the trunks of
birches. In the spring the larvae mature and pupate in
the tree trunk. The adults emerge from the tree at the
end of May or in early June. The adult females begin to
lay eggs on the tree trunks preferably near a wound or
injury. The larva hatches out of the egg and bores into
the tree trunk. The larvae can be in the tree one or two
years.
The main symptom is death of the upper branches of the
tree. All the leaves on affected branches turn brown the
the leaves are entirely brown. The injury should not be
confused with the partial browning of leaves caused by
birch leaf miner. Close inspection of the trunk will
often reveal the adult emergence holes. These can be
either round or semi-circular.
Control involves keeping trees healthy and pesticide
applications. Keeping trees healthy with regular
fertilizer and watering during dry weather will reduce
tree susceptibility. Such measure do not prevent
infestation. Birch trees should not be planted on dry,
adverse sites as they will be more borer susceptible.
Applications of insecticides are timed to kill the larvae
as they hatch out in late May to early June.
At least three birch trees have been reported as being
resistant to bronze birch borer. The are monarch birch,
Betula maximowieziana, the Japanese birch, Betula
platyphylla and the river birch, Betula nigra. The river
birch does not have the smooth white bark that makes birch
a desirable ornamental tree. Resistance can only be
assured after the trees have been used in landscapes and
are found to have little problem with borer.
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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.
For more information about this data base or its contents please contact
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