White pine weevil, Pissodes strobi,
 

Fig. 103 Larva feeding within spruce leader.	Fig. 104 Frass plugs along leader indicate egg laying.	Fig. 105 Shepherd's crook is an early indication of attack.
Fig. 106, Spruce with dead top resulting from earlier attack. Both previous and current year's growth are killed.	Fig. 107 Exit holes made by emerging adult.

Tree Species Attacked: Despite its name, the primary hosts for the white pine weevil are Sitka, white, and Engelmann spruce. Pine and other spruce species are sometimes attacked. Trees 1.5 to 10 m high are preferred.

Insect Description & Damage Symptoms: This insect is also known as the spruce weevil. Larvae are stout, curved, legless grubs. The body is yellowish-white and the heads are light brown. Larvae may reach 1 cm in length by the final instar. Adults are reddish-brown to black with cream markings. Their long, curved snout is characteristic of weevils. Length varies from about 0.5 to 0.8 cm, and the elytra are heavily scaled and mottled in appearance. The first sign of attack appears in spring, when small punctures appear near the tip of the previous year's leader, where the adults feed and deposit their eggs. Resin droplets are associated with these wounds. The larvae feed gregariously down the leader in the phloem, girdling the stem. Mature larvae excavate cavities in the wood and pith and line them with wood chips. Pupation occurs in these "chip cocoons". By mid-summer, the current year's leader on attacked trees will be distorted and wilted. This shepherd's crook gradually changes from yellow to red to brown, and is indicative of weevil attack. In late summer to fall, large holes made by emerging adults may be seen midway down the previous year's leader. By this time, the current and previous year's leaders are usually dead. Signs of previous attacks include deformed or multiple leaders and dead stubs along main stems. Dead stubs are very crisp, break easily, and contain the distinctive "chip cocoons".

Damage: This weevil prefers vigorous, open-grown trees, and causes terminal dieback of at least two years' growth. In addition to growing loss, attacks may reduce timber quality by inducing forked and crooked stems. Repeated attacks may allow less desirable species to become dominant over the host species. Secondary organisms such as heartwood rot fungi may enter through the weevil-killed leaders. A severe, lengthy outbreak may reduce stand volume by as much as 30 to 40%. The best time to evaluate damage is from August to September.

Similar Damage: Frost damage may be confused from a distance with white pine weevil damage. Wind damage can sometimes look like weevil damage when the leaders are young, soft, and flexible. Birds may sometimes break leaders as well. Closer inspection of the terminal will reveal weevil signs, such as adult exit holes, and chip cocoons. Live, newly expanding leaders may droop, causing some confusion between healthy leaders and newly attacked shepherd's crooks.

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BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated February 18, 2002