Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001097
11/12/99
PICEA INSECT PROBLEMS
Two adelgids commonly attack spruce. Eastern spruce gall
adelgid forms pineapple like galls (Vis. 2) at the base of
twigs. Galls caused by Cooley's spruce gall adelgid look
like miniature cones (Vis. 1) at the branch tips. The
adelgids do not kill trees unless the infestation is heavy.
A few galls on a large tree are not serious.
Bagworm lives in a two to three inch long sack built from
needles. The insect overwinters as an egg in the sacks of
the females. The injury consists of feeding on the foliage
with most of the injury near the top of the tree. Control by
hand-picking the bags in winter.
Spruce budworm larvae (Vis. 4) feed on developing buds and
young needles. The yellowish brown caterpillars are
difficult to see.
The spruce needle miner makes a small hole (Vis. 5) in the
base of a needle then mines out the center. Dead needles
are webbed together and can be found on infested twigs.
Elongated white flecks on the needles may be Pine Needle
Scale. The insects suck juices from the foliage causing it
to become discolored. Heavy infestations will reduce tree
health. Dormant oil sprays in late fall or early spring will
control the problem.
Spider mites can be problem in summer after hot dry
weather. The small insects can't be readily seen with the
naked eye. The first noticeable symptoms are yellowing of
the oldest needles (Vis. 3) on infested branches. Close
inspection with a magnifying glass will confirm the presence
of the mites.
Bark beetles bore into trunks making small holes scattered
up and down the trunk. The holes look like shotholes.
Keep trees healthy as stressed trees are more susceptible to
attack. .
Related information.
Pesticide Recommendations
Eastern Spruce Gall
Cooley's Spruce Gall
Spruce Needle Miner
Spider Mites
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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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