Rice weevil

Sitophilus oryzae (L.)


Primary pest; grain feeder
Order: Coleoptera
Family: Curculionidae
Acronym: SOR


  • Adult is small (2.5 to 4 mm), dark brown with 4 distinct reddish to reddish yellow patches on the elytra.
  • Adult is identical in external appearance to the maize weevil (Sitophilus zeamais); dissection required to distinguish between the species.
  • Larvae are white, legless grubs that develop within the kernel and will not be detected in sieve samples or Berlese funnel samples.


Similar species

Commodities affected

  • Rice, wheat, barley, occasionally peas
  • Raw processed cereals such as pasta

Signs of infestation

  • Increased moisture levels and heating on the surface
  • Seeds with round holes formed by exiting adults


  • Adults feed on whole seeds or flour.
  • Larvae develop in seeds or pieces of seeds or cereal products large enough to house larvae but will not develop in flour unless it has been compacted.
  • Feeding contributes to heating and infested grain is often damp due to moisture added by the insects’ respiration.

How to control

Geographic range

  • Is distributed worldwide and across Canada
  • Prefers tropical or subtropical environment but can survive temperate regions in protected situations

Life history

  • Adults are able to fly.
  • Adults live 4 to 5 months.
  • Females generally lay eggs within a kernel but they may lay multiple eggs per kernel and more than 1 larvae can develop within a single kernel.
  • Adults make a small, circular emergence hole , compared to large, oblong emergence hole made by the granary weevil.


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