Black Vine Weevil

Scientific Name: Otiorhynchus sulcatus

Black vine weevil are beetles whose larvae feed on the roots of evergreen yew, arborvitae and rhododendron often causing decline and death. Adult beetles feed on the foliage leaving semi circular notched leaves behind. Adults feed at night, so the most obvious symptom is leaf notching.

Attacks: Yews, rhododendron, arborvitae

What you will see:

• Adults notch leaves and flowers
• Larvae feed on roots and can kill plants

Life cycle:

• Overwinter as larvae
• Adults emerge from June to July
• After feeding for 2-3 weeks, adults begin to lay eggs
• Adults active through September
• Eggs are laid on the ground in leaf litter
• Larvae feed until they overwinterAdults may also overwinterOne generation per year
• All weevils are females (no males exist)

Treatment and Applications:

Insecticides (60% effective):

• Soil drench for overwintering larvae
• Foliage spray for adults 2-3 sprays

Cultural practices:

• Expose eggs to desiccation and predation
  • Reduce soil moisture
  • Remove organic matter from base of plants
• Create mechanical barriers to prevent infestation
  • Weevils cannot fly, will fall into pits
  • Barriers are only effective as a preventative measure

Biological control:

• Parasitic Nematodes:
  • Make sure nematodes are alive prior to treatment
  • Saturate soils before and after treatment
  • Very effective in container plants
  • 50/50 or less effectiveness in landscapes

 

An integrated approach

When caring for urban trees it is important to make a complete evaluation of all environmental conditions to accurately diagnose all stress factors and prescribe care based on specific circumstances. This prescriptive care will help your tree meet its full potential.