Pales Weevil
Contact: Eric Day, Manager, Insect Identification Laboratory
ENTOMOLOGY PUBLICATION 444-229, August 1996
Pales Weevil
Plants Attacked
Pales weevil feeds on all pines within its range. It will also
feed, although to a lesser extent, on Douglas-fir, fir, hemlock,
juniper, larch, northern white-cedar, and spruce.
Description of Damage
During the months of June through August look for the following
symptoms: 1) Dead seedlings or dead shoot tips on larger trees.
These are sometimes called flags because the dead tan twig
contrasts with the green tree. 2) Pitch or resin bleeding on
twigs, shoots, and at the base of flagged shoots. Adult pales
weevils feed on the stem bark of new growth and pitch oozes from
the wound. This pitch will callous over and appear as a white
patch on the bark. If the damage is severe enough, the twig will
die. The adults are involved in the transmission of Procerum
root disease. The larval stage, which is not considered a pest,
feeds mostly on the bases of dead or dying trees or on stumps.
Douglas fir, shoot death caused by Pales Weevil.
White pine, close-up of damage in shoot.
White pine, more damage by Pales Weevil.
"Flagging" (single dead branch) caused by Pales Weevil.
Ideal situation for Pales Weevil problems, pine stumps mixed with mature trees.
Identification
The adult is a small reddish-brown to black weevil about 1/3 of
an inch in length. It has a line of scales ranging in color from
orange to yellowish-white on its head, and patches of similar
scales on its elytra (wing covers). The larva is pale creamy
white and C-shaped in appearance. It has a dark head and no
legs. The pales weevil, Hylobius pales (Herbst), is in the
family Curculionidae, order Coleoptera.
Scouting Tips
The best way to scout for the adults is to spread a sheet under
the tree after dark and shake the tree: the weevils will drop
down. To look for the larvae, take a knife and cut back the bark
on stumps or on the base of dead trees. The larvae make
galleries that run mostly with the grain of the wood. Full grown
larvae and pupae can be found in chip cocoons under the bark,
which are small depressions filled with slivers of wood.
Life History
Female weevils are drawn to the smell of resin on fresh cut
stumps and on damaged and recently dead pine trees. The time
they are actively seeking these sites is in the spring between
March and June. Once located on a suitable host they lay their
eggs on the roots. The larvae feed downward in long tunnels, but
work their way to the outer bark above the soil surface to
pupate. The new adults emerge in mid-August and mid-September
and feed on shoots and twigs. Eventually they seek a site to
overwinter, usually in litter below the tree, and emerge in the
spring to start the cycle again.
Control
The key to pales weevil control has two main components and in
most cases these will be all that is necessary. 1.) The removal
of old stumps and dead trees, as these are the weevil's breeding
sites. 2.) If stumps are left in the field, then drench stumps
and surrounding soil with a registered insecticide between early-
April and mid-May. Currently recommended in the Virginia Pest
Management Guides are lindane or Asana XL, which need to be mixed
with kerosene. Dursban mixed with water is also recommended.
Only stumps cut since the previous year need be treated. Stumps
older than two years do not need to be treated. One possibility
of control, if stumps must be left in the field, is to leave a
whorl of live pest free branches on the stump. These stumps are
unattractive to weevils. Another method for control is to delay
replanting until two years after harvest, but this may cause
problems if there are nearby plantings with fresh stumps. Pales
weevils can fly and may come to your planting from a distance,
depending on wind direction and availability of other host trees.
Additional control may be needed in the following situations:
If flagging is observed in August or September, treat for adult
weevils feeding in the trees (do not use kerosene mixture when
treating live trees). Damage to new plantings can be controlled
by dipping seedlings in an Imidan root dip.
Remarks
Pales weevil belongs to a group of weevils called pine
reproduction weevils. These weevils feed at the base of pines
and on branches of live pine trees. This group includes the
pales weevil, deoadar weevil, pitcheating weevil, and the pine
root collar weevil. The pitcheating weevil is found to the south
of Virginia and the pine root collar weevil is found to the
north; neither is considered a pest in Virginia.
Prepared by Eric Day. Department of Entomology, Virginia
Polytechnic Institute and State University, Blacksburg, Virginia
24061-0319.