Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001741
11/12/99
Cooley's Spruce Gall Adelgid
The immature females overwinter on spruce trees. The
female matures in the spring and lays eggs on the branch
tips. The eggs hatch and nymphs move to the new growth
and feed at the base of the needles. The feeding causes
formation of a gall (Vis. 1) that encloses the insects. In
midsummer an opening forms at the base of each needle on
the gall. The insects leave the gall through these
openings and become winged females. They fly to Douglas-fir
or a spruce and feed on these trees as though they
were woolly aphids.
The most visible symptom is the galls formed at the branch
tips. The branch tips appear to have swollen and drooped.
They are sometimes described as small 'cones'.
Sprays must be applied before the insects are enclosed in
the gall.
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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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