Integrated Pest Management
Root Weevils
Otiorhynchus spp.
Adult black vine weevil (Joseph Berger, Bugwood.org)
Black vine weevil larva (Peggy Greb, USDA Agricultural Research Service, Bugwood.org)
Root weevil feeding damage (Whitney Cranshaw, Colorado State University, Bugwood.org)
Pest Description
- adults: 1/4 – 1/2 inch; square snout; black with white/brown flecks
- larvae: up to 1/3 inch long; white grubs without legs; brown head capsule
Host Plants, Diet & Damage
- many hosts: lilac, euonymous, strawberry, broadleaved evergreens preferred
- larval feeding on host plant roots can lead to weakened plants causing dieback
- adults create unsightly marginal leaf notches
- considered a nuisance pest when entering homes
Biology, Life Cycle & Damaging Life Stage
- overwinter as nearly full-grown larvae; some as adults
- larvae resume feeding in the spring
- adults emerge around June and are active through fall
- eggs are laid in the soil around the plant base
- adults do not fly; fall to the ground when disturbed
- nocturnal feeders
- one generation per year
- larvae and adults are damaging
IPM Recommendations
- Manage trees to improve or maintain overall health.
- Monitor plants for marginal leaf notching.
- Minor damage may be tolerated.
- Apply an insecticide (pyrethroid) to foliage in the evening to control feeding adults when damage is present.
- Apply a systemic neonicitinoid as a soil drench in May or after leaves have expanded in spring.