White Pine Weevil

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.