Rice weevil
Sitophilus oryzae (L.)

Classification

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

Description

  • 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 insects

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

Damage

  • 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.

Images

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Did you know?

The rice weevil causes damage similar to that of the maize weevil and the granary weevil.

Video of rice weevil

Transcript

Many adult rice weevils move amongst grains of wheat. Some of the grains of wheat have holes that are typical of damage caused by rice weevils.