Viburnum: Root weevils

Biology

Root weevil larvae feed on the roots and bark of plants near the crown. The white grubs are found in the soil around the roots. Heavy feeding by root weevil larvae can cause girdling of roots or crown, resulting in decline or death of the plant. Adults may feed on leaves, causing minor to severe notching of leaf margins. Adult root weevils range in size from 1/4″ to 1/2″ long. They are brownish to black, flightless beetles which climb into the foliage to feed at night.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Hand-pick and kill night-feeding adults.
• Apply beneficial nematodes which kill weevil larvae. The nematodes are used as a soil drench in moist soils over 55 degrees F (mid-fall in western Washington). Read and follow the label directions carefully.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Adult control should begin when adults emerge late May-June. Apply to foliage.
• Homeowners should not make foliar applications to trees over 10 ft tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Safer Brand BioNEEM Multi-Purpose Insecticide and Repellent Concentrate [Organic]
  Active ingredient: azadirachtin [EPA registration number: 70051-6-42697]
• Safer Brand Garden Defense Multi-Purpose Spray Concentrate [Organic]
  Active ingredient: clarified hydrophobic extract of neem oil [EPA registration number: 70051-2-42697]
• This list may not include all products registered for this use.

Additional Images