•  Step 2
  • Sitka Spruce Weevil Hazard Decision Tool for Vancouver Island

    Step 1 Step 2 Silviculture

    STEP 2 - Assess the site factors below to determine if the hazard rating should increase or decrease relative to the temperature (degree days) at your site. See an example.

    Key Vancouver Island site factors affecting weevil hazard

    Site factor

    Lower hazard

    (annual attack rates <20%,

    severity low to moderate)

    Higher hazard

    (annual attack rates >20%,

    severity moderate to high)

    BEC unit

    CWHvh, CWHvm2 CWHvm3, CWHmm, MHmm

    CDFmm, CWHxm, CWHdm, CWHvm1

    Fog belt



    Ss leader position




    Deciduous (alder, rarely cottonwood)



    Poor to moderately rich (B to D)

    Very rich (E)

    Mineral soil depth

    <50 cm

    >50 cm

    Organic soil depth

    >40 cm

    <40 cm


    Imperfect (flat/undulating/hummocky)

    Well to moderately well

    Ss height

    <2 m and >18 m

    2-18 m tall


    >1250 sph

    <1250 sph


    >40% ground cover

    <40% ground cover


    Cool (285-135)

    Warm (135-285)

    Indicator plants

    Click on link for more info

    Click on link for more info

    Site factors that don’t (significantly) affect weevil attack rates

    • Density of Sitka spruce on low hazard sites.
    • Slope, except on imperfectly drained flat sites that have less attack.
    • Besides the species listed in the table, percent cover of other species and of vegetation class (bryophytes, herbs) also had no relationships with weevil attack.
    • Soil coarse fragment content or texture (except for cobbly substrates, which had low attack rates).

    Updated May 2009