Pest profile

Obscure Root Weevil

Sciopithes obscurus · Coleoptera: Curculionidae[2]

The obscure root weevil is a gray, flightless weevil that notches leaves at night; its larvae feed on the roots of blueberries and other plants.[1]

Obscure root weevil, a gray, snout-nosed weevil, on a branch
Obscure root weevil, a gray, snout-nosed weevil, on a branch. (c) giantcicada, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are 6 to 8 mm long and mostly gray with a wavy brown line across the wing covers.[1]
  • Leaves show notches from adult feeding in early summer.[1]

Look-alikes

Look-alikeHow to tell them apart
Strawberry root weevilTheir larvae look alike and have similar life cycles; obscure root weevil adults are gray with a wavy brown line across the wing covers.[1]

Where it lives

The PNW Insect Management Handbook covers it on blueberries and caneberries in the Pacific Northwest.[1]

US map: public records from 4 states since 1990 (GBIF).

Biology and life cycle

Larvae overwinter in the soil, pupate from April to June, and adults emerge in late spring.[1]

Adults can't fly; they walk or ride on equipment, and all are females that can lay hundreds of eggs in or on the soil from June to September.[1]

Unlike other blueberry weevils, many stay in the foliage by day and feed at night; there's one generation a year.[1]

Damage and signs

  • Larvae feed on roots, while adult leaf notching does little harm.[1]

Health risk

It feeds on plants; the PNW Insect Management Handbook mentions no risk to people.[1]

Control

Prevention

Check foliage on warm, still nights, or wrap trunks with cardboard and check under it in early morning.[1]

Cultivating soil in April and May before planting can kill overwintering larvae.[1]

Biological control

Beneficial nematodes (Heterorhabditis and Steinernema) applied to the root zone as a fall drench have shown some effect on larvae.[1]

Pesticides

No products are registered for home-garden control in the PNW handbook's blueberry listing.[1]

Common questions

What is notching my blueberry leaves at night?
Likely obscure root weevils, which feed on foliage at night.[1]
Do beneficial nematodes work on obscure root weevil?
They've shown some effect on larvae when drenched into the root zone in fall.[1]

Sources

  1. Pacific Northwest Pest Management Handbooks (OSU, WSU, University of Idaho), “Blueberry: Obscure root weevil (Insect Management Handbook).” pnwhandbooks.org/insect/small-fruit/blueberry/blueberry-obscure-root-weevil (accessed 2026-10-06)
  2. iNaturalist, “Sciopithes obscurus taxon page (order and family).” www.inaturalist.org/taxa/366563 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.