Maize weevil
Sitophilus zeamais Motschulsky

Classification

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

Description

  • Adults are identical in external appearance to the rice weevil (Sitophilus oryzae); dissection required to distinguish between the species.
  • Adults are reddish brown beetles with a characteristic long weevil snout and have 4 yellow to red spots on the elytra.

Similar species

Commodities affected

  • Grain, pasta

Signs of infestation

  • Damaged kernels with ragged holes
  • Increased heat and humidity in pockets of grain

Damage

  • Damage is distinctive; both adults and larvae feed directly on the kernel.
  • Larvae feed internally and newly emerged adults leave a ragged exit hole and will also feed on the damaged kernel.
  • Maize weevil infestations produce heat and moisture.

How to control

Geographic range

  • Is abundantly distributed in tropical environments throughout the world, where it is able to infest standing crops
  • Is less common in temperate zones and, in Canada, has only been found in Ontario and Quebec

Where found

  • Is found in granaries, stores, elevators
  • Tends to aggregate within grain bulks, making populations difficult to detect

Life history

  • Adults can fly.
  • Aadult beetles are long-lived (3 to 6 months or more).
  • Adult females lay eggs singly by first chewing a small hole in the grain, then depositing the egg into the hole then sealing with a mucus plug
  • Larvae hatch and feed internally within the kernel.

Images

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Did you know?

The maize weevil is commonly associated with feeding on corn, rice and on other raw or processed cereals.