WSU Extension

Hortsense

Common Insects & Mites : Root weevils
(revision date: 4/30/2013)


Biology
Several species of root weevils can be serious pests of landscape plants including azalea, rhododendron, rose, and strawberry. The black vine weevil is perhaps the most common. Adult weevils create characteristic notchings along leaf margins of countless plant species. The weevil larvae also can be serious pests, particularly in nursery plants. The larvae feed on roots and in some cases girdle crowns and lower stems.
Management Options

Non-Chemical Management
  • Apply beneficial nematodes which kill the larvae. They are used as a soil drench in moist soils over 52 degrees F (mid-fall in western Washington).
  • Plant resistant varieties when available. Your county extension agent or WSU Master Gardeners can furnish a list.
Select non-chemical management options as your first choice!

Chemical Management

Adult control should begin when adults emerge late May-June or when first signs of notching appear on new leaves. A follow-up spray may be necessary about a month later. Beneficial nematodes can be applied to control the larval stage if soil temperatures are warmer than 52 degrees F.

Images
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Caption: Black vine weevil adult and leaf damage
Photo by: A.L. Antonelli
Caption: Root weevil damage on peony
Photo by: E.H. Beers
Caption: Root weevil larval damage
Photo by: A.L. Antonelli
Caption: Adult root weevil damage
Photo by: E.P. Breakey
Caption: Root weevil larvae
Photo by: A.L. Antonelli
Caption: Root weevil damage on strawberry
Photo by: A.L. Antonelli
Caption: Root weevil damage on rhododendron
Photo by: A.L. Antonelli