Bean weevil

Acanthoscelides obtectus (Say)

Classification

Primary pest; Grain feeder
Order: Coleoptera
Family: Chrysomelidae
Acronym: AOB

Description

  • Adults are 3 to 4 mm long, globular in shape with long legs.
  • Elytra do not reach the end of the abdomen, leaving the last terga exposed.
  • Last upper abdominal segment is covered with yellowish hair (setae).
  • Inner ridge of the ventral margin of the hind femur has three or four "teeth".
  • Larvae are white and grub-like, having reduced legs.

Images

Similar species

Commodities affected

  • Beans, broad beans, lentils, chickpea, soybean

Signs of infestation

  • Damaged seeds with entrance or exit holes

Damage

  • Damage is distinctive with tiny dot-like entrance holes and larger, round exit holes and excavated seed.
  • Large populations may reduce stored seed to dust.

How to control

Geographic range

  • Is distributed worldwide
  • Is distributed across Canada

Where found

  • Primarily attacks stored beans but may attack plants in the field
  • Establishes well in heated storages and granaries

Life history

  • Adult bean weevils feed on bean plant foliage and seed pods.
  • Females lay eggs inside the seed in storage or lays multiple eggs on the surface of a pod in the field.
  • Larvae develop in growing or stored bean seeds.
  • After pupation within the seed, the adult chews an exit hole through the seed coat.
  • In heated storage conditions, the adult bean weevil can emerge at any time of the year and breed continuously.

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