Pest profile

Rose Curculio

Merhynchites bicolor · Coleoptera: Attelabidae[2]

Rose curculio adults drill holes in rose buds, which can kill the bud or leave ragged holes in the open flower.[1]

Rose curculio, a red snout weevil with black legs, on a rose bud
Rose curculio, a red snout weevil with black legs, on a rose bud. (c) Alex Day, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are reddish-black snout weevils about 1/4 inch long.[1]
  • They prefer yellow and white roses.[1]

Look-alikes

Look-alikeHow to tell them apart
Fuller rose beetlePale brown, flightless weevils about 3/8 inch that chew notched edges on leaves and flowers at night.[1]

Where it lives

UC IPM covers it among the insects that attack roses in California gardens.[1]

US map: public records from 24 states since 1990 (GBIF).

Biology and life cycle

Eggs are laid inside buds and larvae feed within; mature larvae drop to the ground to overwinter and pupate in soil.[1]

Adults emerge in spring, and there's only one generation a year.[1]

Damage and signs

  • Many weevils can also kill terminal shoots.[1]

Health risk

It feeds on plants; UC IPM mentions no risk to people.[1]

Control

Sanitation

Destroy buds infested with larvae.[1]

Traps and physical control

Hand-pick adults or shake them off over a bucket of soapy water.[1]

Pesticides

A broad-spectrum insecticide may be used against adults only if the infestation is severe.[1]

Common questions

What's drilling holes in my yellow rose buds?
Rose curculio, a reddish-black snout weevil that prefers yellow and white roses.[1]
How many generations of rose curculio are there?
Only one a year; adults emerge in spring.[1]

Sources

  1. University of California Statewide IPM Program, “Roses: Insects and Mites (Pest Notes).” ipm.ucanr.edu/home-and-landscape/roses-insects-and-mites/ (accessed 2026-10-06)
  2. iNaturalist, “Merhynchites bicolor taxon page (order and family).” www.inaturalist.org/taxa/70051 (accessed 2026-10-06)

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