Rice weevil

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 species

• Granary weevil (Sitophilus granarius)
• Maize weevil (Sitophilus zeamais) – morphologically nearly identical

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

• Control grain insect pests

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.

Video

• Video of rice weevil