White Pine Weevil

    White Pine Weevil

    Pissodes strobi

    white pine weevil

    Adult white pine weevil (Dave Powell, USDA Forest Service, Bugwood.org)

    white pine weevil larvae

    White pine weevil larvae and girdling damage (William M. Ciesla, Forest Health Management International, Bugwood.org)

    white pine weevil damage

    White pine weevil damage to leader (Scott Tunnock, USDA Forest Service, Bugwood.org)

    Pest Description

    • adults: ~ 1/4 inch; long snout; black with white/orangish flecks
    • larvae: up to 3/8 inch long; white grubs without legs; brown head capsule

    Host Plants, Diet & Damage

    • primarily blue spruce; white pine
    • common at high elevations (e.g., Wasatch and Summit counties) or in nursery situations
    • larvae feed under the bark of terminal leaders
    • larvae girdle young (1-3 years) leader growth only
    • damaged trees have bushy appearance; reduced growth
    • dead leaders turn brown and curl (shepherd’s crook)
    • dead leaders riddled with holes and stringy frass
    • severe damage is rare

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as adults in duff around trunks
    • adults migrate up trunks (or fly) to canopy in late spring
    • feed and lay eggs below the terminal buds
    • feed and pupate within the terminal and emerge from late-July through fall
    • minor adult feeding occurs until dormancy in fall
    • one generation per year
    • larvae are the primary damaging stage

    IPM Recommendations

    • Manage trees to improve or maintain overall health.
    • Monitor spruce trees in June/July for terminal death.
    • Prune infested terminals prior to adult emergence.
    • Apply an insecticide (pyrethroid) to target feeding/egg laying adults on the top 3 to 4 years of terminal growth and the lower trunk prior to emergence in spring.
    • Apply a systemic neonicitinoid soil drench in fall to control larvae the following year.