Viburnum: Root weevils

• Categories: Ornamentals Shrubs Viburnum Viburnum Insects
• Last review date: 2026-08-29 08:37

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

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

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

• 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

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.

• Safer Brand Neem Oil Concentrate
  Active ingredient: NEEM Oil, Clarified Hydrophobic Extract
  EPA registration number: 70051-2-42697
• Azera Gardening [Organic]
  Active ingredient: azadirachtin, pyrethrins
  EPA registration number: 1021-1872
• This list may not include all products registered for this use.