Yosemite bark weevil, Pissodes schwarzi,

Fig. 116 Yosemite bark weevil.	Fig. 117 Lower bole and root attack of lodgepole pine by the Yosemite bark weevil. Note the distinctive chip cocoons

Tree Species Attacked: The primary host is young lodgepole pine, but it has been found in other pines, spruces, and western larch.

Insect Description & Damage Symptoms: The adult beetles are rough-surfaced, mottled, reddish-brown to dark brown, 5 to 7 mm in length, and have the distinctive weevil snout. The beetles bore under the bark in the bole, root collar, and large roots of stressed or dying trees. They are commonly found in lodgepole pine affected by serious damaging agents, such as comandra blister rust. Overwintering adults primarily lay their eggs in May through July. The creamy white larvae feed throughout the summer, and overwinter under the bark in distinctive "chip cocoons".

Damage: Spacing operations can allow Yosemite bark weevil populations to build up in the stumps, at which point they can attack and kill living trees, especially ones that are under stress, such as during drought conditions.

Similar Damage: Warren's root collar weevil also attacks at the root collar. However, it is a much larger weevil than the Yosemite bark weevil, and has the distinctive pitch tube shelters surrounding it. In contrast, the Yosemite bark weevil larvae create chip cocoons.

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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