Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001122
11/12/99
PINUS INSECT PROBLEMS
Aphids will infest branches and suck plant juices. They
produce honeydew which may support sooty mold.
European pine shoot moth causes young shoots to fall
over. Clumps of resin will form on shoots where the insects
bore into the shoots. Insect injury causes trees to become
bushy and have multiple leaders. The insects can be found
in the shoots during May. Use properly labeled pesticides
when caterpillars are moving from overwintering sites to new
shoots. This occurs in mid to late April. Another
treatment may be applied in late June or early July when the
eggs hatch.
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. .
Sawfly larvae caterpillars (Vis. 1) are variously colored
but generally feed in groups on the needles. Chemical
controls applied when larvae are small are more effective.
Some sawfly larvae will flex or rear back in unison when
disturbed.
Elongated white flecks (Vis. 2) 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.
Pine spittle bug lives and hides in a foamy mass. These
insects are generally not a serious problem but the feeding
sites can be entrances for shoot blight.
Mites cause older needles to become yellowed or stippled.
Zimmerman pine moth larvae bore into the trunk. The
only outward symptoms may be masses of hardened pitch on the
branches. The portion of the stem above the pitch mass may
die. On Scotch and Austrian pines the pitch mass may be on
the main stem. On other pines it may be on shoots near the
top of the tree.
The larvae of white pine weevils feed on the sapwood of the
leaders. The leader is killed and the site shoots may be
injured. First symptoms are drops of resin on the leaders
where the weevils are feeding. The leaders die when the
shoot is girdled. Prune out and burn infested terminals
before July 15.
Eastern pine shoot borer caterpillars bore through the
center of shoots. The weakened shoots droop, curl or break
and turn yellow. Cutting the shoots lengthwise will expose a
sawdust-like material. Pesticides are not effective after
the injury is obvious. Chemical controls must be applied in
mid May.
Jack pine budworm eats the needles at the branch tips. The
insect also uses webbing to attach needles to the branches.
The caterpillars will be present in the webbed foliage from
mid May to early July.
Pine tortoise scale sucks juices from plants leading to
discolored foliage and stunted plants. Closer examination of
infested branches will reveal brown, mottled rounded scales.
The scales produce sticky honeydew that may coat the part of
the tree beneath the infestation.
Webworms form nests that consist of needles and frass webbed
together. The needles closest to the nest will be chewed.
The pine false webworm is green and feeds during May and
June. The pine webworm is a problem in July and August and
is yellowish-brown.
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. .
Pine bark adelgids infest the trunks of trees where they
suck sap. The adelgids produce a white, waxy coating. When
large number of the pests are present, the infested area
will be almost completely white. Sprays of dormant oil
usually control this pest.
Related information.
Pesticide Recommendations
Pine Needle Scale
European Pine Sawfly
Pine Bark Adelgid
Spittlebugs
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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