Blackvine Weevil

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.

Treatment Strategy

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 before if detected, treatment should begin. Soil drenches with imidacloprid are successful for control of grubs. Foliar sprays of Upstar Gold can be used to control adults, but multiple applications will be necessary as adults do not feed every night. A soil application of Xytect in mid-to-late August targets the first instar stage of the weevil population, which are much easier to kill than the later instar larvae.

Other Treatment Practices

  • Bunching burlap around the base of plants can be used as a trap. Weevils will feed on the plant during the night and hide in the burlap during the day. The burlap can be removed and checked for adults.

Limb/Foliar Spray or Soil Application Using Transtect

Limb/Foliar Spray or Soil Application Using Xytect 2F

Limb/Foliar Spray or Soil Application Using Xytect 75WSP

Foliar Spray Using Up-Star Gold

Expected Results

Depending on the situation, control is not always needed. Multiple sprays may be necessary as adults do not feed every night.

Signs of Damage

  • In May or June, adults remove crescent shaped sections 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 and will quickly scurry when shined with light
    • They are black or dark brown and 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
  • Eggs are generally found in the leaf litter under host plants

Photo: John A. Weidhass
Virginia Polytechnic Institute and State University, Bugwood.org

Photo: David Gent
USDA Agricultural Research Service, Bugwood.org

Photo: Peggy Greb
USDA Agricultural Research Service, Bugwood.org

Trees At Risk

Black Vine Weevil will feed on over 100 host plants, however yew (Taxus spp.), rhododendron (Rhododendron spp.) and hemlock (Tsuga spp.) are among the most common host species.

Biology

  • 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 (148-400) in late May to early July and feed on leaves.
  • One generation per year.

A Treatment 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 of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments by forestryimages.org

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