•  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

    Inside

    Outside

    Ss leader position

    Shaded

    Exposed

    Overstorey

    Deciduous (alder, rarely cottonwood)

    None

    SNR

    Poor to moderately rich (B to D)

    Very rich (E)

    Mineral soil depth

    <50 cm

    >50 cm

    Organic soil depth

    >40 cm

    <40 cm

    Drainage

    Imperfect (flat/undulating/hummocky)

    Well to moderately well

    Ss height

    <2 m and >18 m

    2-18 m tall

    Density

    >1250 sph

    <1250 sph

    CWD

    >40% ground cover

    <40% ground cover

    Aspect

    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