Forest Science Program

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User-friendly web tool to support silviculture for sitka spruce on the south coast

Author(s) or contact(s): J. Krakowski
Source: Forest Science Program
Subject: Forest Genetics, Forestry General, Silviculture General
Series: Extension Note
Other details:  Published 2010. Hardcopy is available.


Pissodes strobi, the terminal weevil that preferentially attacks leaders of Sitka spruce between 2 and 15 m tall, has become a major deterrent to selecting this species for reforestation. Successful weevil attacks kill the leader and a lateral shoot takes over, forming a crook in the stem. Repeated and severe attacks prevent seedlings from reaching free-growing status, and render trees unmerchantable due to bole defects. However, trees may recover from less severe attacks and attain good form upon maturity. Weevil hazard is therefore better indicated by the severity of the effects on form than by the number of attacks. Decades of research and tree improvement have culminated in available terminal weevil resistant Sitka spruce seed for reforestation. Foresters can expect fewer than half the attack levels of local wild stands from bulk seedlots from the superior provenances Haney and Big Qualicum, and over 80% reduction from class A orchard seed (King and Alfaro 2009). The objective of this study was to develop a user-friendly, accurate web tool that foresters could use to support reforestation prescriptions for sites on Vancouver Island where Sitka spruce is an appropriate species.

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Updated January 27, 2010