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White Pine Weevil Fact Sheet
Fact Sheets
> Insect Fact Sheets > White Pine
Weevil
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Pinus strobus(Eastern white
pine) -
leader dieback from white pine weevil damage -- Photo courtesy
of Michael Masiuk |
The white pine weevil, Pissodes strobi (Peck), is considered the
most destructive insect pest of eastern white pine in Pennsylvania
with either forked or deformed trees resulting from repeated infestations.
Trees become susceptible to injury when they reach a height of
about three feet, and trees exposed to direct sunlight are more
susceptible to attack . |
Plants Attacked
| Common Problem |
Eastern white pine |
Pinus strobus |
| |
Jack pine |
Pinus banksiana |
| |
Norway spruce |
Picea abies |
| |
|
|
| Occasional Problem |
Swiss stone pine |
Pinus cembra |
| |
Austrian pine |
Pinus nigra |
| |
Red pine |
Pinus resinosa |
| |
Scotch pine |
Pinus sylvestris |
| |
White spruce |
Picea glauca |
| |
Oriental spruce |
Picea orientalis |
| |
Colorado blue spruce |
Picea pungens var. glauca |
| |
|
|
| Rarely Attacked |
Himalayan Pine |
Pinus wallichiana
|
| |
Serbian spruce |
Picea omorika |
| |
Douglas-fir |
Pseudotsuga menzesii |
Insect Identification
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| White pine weevil
adults -- Photo courtesy of Dave Shetlar
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| White pine weevil eggs and
larva --Photo courtesy of Pennsylvania Department of Agriculture
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Adults are 1/4" long reddish-brown
weevisl with white patches on the end of their wing covers. Like
most weevils, the adult has a long snout-like beak from which
knobbed antennae arise. Larvae, living beneath the bark, are white,
legless, with a distinct brown head. They are 5/16" long when
mature.
|
Life History
| Winter |
Adults spend the winter in the duff under trees. |
| Spring |
From mid-March to mid-April, adult females climb
trees to feed on leaders. Females lay one to five eggs in the
feeding wounds in tree leaders. The eggs hatch in about a week,
and the larvae feed just below the bark, tunneling downward,
girdling and killing the shoot as they go. |
| Summer |
Larvae mature and pupate in mid-July in spaces carved
into the sapwood and lined with shredded wood. Adults emerge in
late-July and August and briefly feed on the upper tree branches. |
| Fall |
Adults return to the duff to hibernate. |
Damage Symptoms
 |
| White pine weevil feeding
injury on leader of Pinus strobus- eastern white pine
-- Photo courtesy of Michael Masiuk |
The first symptom of attack by this pest is glistening droplets
of resin on terminal leaders in late March and April. This is
the result of punctures made by adults in the process of feeding
and cutting egg-laying sites. Larvae do the most damage as they
tunnel downward in the leader, causing the shoot to wilt and
eventually die. Repeated infestations in successive years results
in a deformed or forked tree.
|
| Biological |
Natural enemies do not provide adequate control. |
| Mechanical |
Prune infested leaders. As soon as the leader droops,
prune the leader out just below where the bark discoloration stops.
Remove the pruned leader containing the larva from the site. Corrective
pruning of the injured top involves removing all but a single
shoot (one of the largest) at the topmost healthy whorl. This
promotes healing, resumption of vertical growth, and straightening
of stem form. |
| Cultural |
Planting the trees in partial shade protects the
leaders from weevil attack by encouraging less preferred bark
thickness and bark temperature. However, the disadvantage of partial
shade is a reduced rate of growth. |
| Resistant Varieties |
Researchers at Cornell University looked at resistance
in selected exotic white pines to this pest. They found that Balkan
pine, Pinus Peuce, and western white pine, Pinus monticola
showed the greatest resistance to the weevil. However, western
white pine is more susceptible to white pine blister rust, a bark
disease, and also was more sensitive to winter injury. While Balkan
pine was more winter hardy, it was more susceptible to needle-blight diseases. |
| Chemical |
Spray only the leader with a registered insecticide in the
spring (late-March through April) when the sap flow from the
adult feeding is observed.
Control
Measures for White Pine Weevil
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 download
White Pine Weevil Fact Sheet
Authored by: Michael Masiuk, Commercial Horticulture
Extension Agent, Allegheny County, Pennsylvania
Last Updated: Tuesday, February 11, 2003
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