Blackvine Weevil Diagnostic Guide
The black vine weevil, Otiorhynchus sulcatus, is native to Europe and spread to the US through nursery stock. Originally only a pest on the East coast, it has since spread to much of North America. This is a pest mainly found in the nursery setting, though it attacks residential plants as well. It prefers yew (Taxus spp.), rhododendron (Rhododendron spp.), and hemlock (Tsuga spp.), though it will feed on over 100 host plants. Adults do mainly aesthetic damage and control is not always necessary. Larvae feed on roots in the soil and can kill entire crops very quickly.
Trees at Risk
Black vine weevil will feed on over 100 host plants. However, yew, rhododendron, euonymus, and hemlock are among the most common host species.
Signs of Damage
- In May or June, adults remove crescent shaped notches of broadleaf leaves and chew off tips of evergreen needles.
- Larvae feed beneath the soil, killing roots from July into the fall.
- If soil moisture is high the grubs may attack and girdle the main stem.
- Adults are about 1/2” long, black, and have a snout that is distinctive of weevils.
- They are nocturnal.
- Adults are not able to fly.
- They will be seen in May or June.
- Larvae are C-shaped grubs about 5/8” long with a brown head.
- They can be seen from July into the fall.
- Eggs are small and white/brown. They are generally found in the leaf litter under host plants.
- Eggs hatch in late July/early August.
- Small young larvae feed on small roots. As larvae grow they feed on progressively larger roots.
- By late fall the grubs have matured.
- Grubs enter a prepupal stage and overwinter underground.
- Adults emerge in late May to early July and feed on leaves.
- One generation per year.
Infestations often begin from infested nursery stock. All stock should be inspected to make sure no grubs are present. It is ideal to control adults before they have a chance to lay eggs. Therefore, as soon as damage is present, or when the weevil is detected, treatment should begin. Soil drenches with Xytect™ are successful for control of grubs.
Depending on level of visual damage, control may not always be needed. However, pest may be successfully controlled with systemic treatment applications.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org