Lesser grain borer
Rhyzopertha dominica (F.)


Primary pest; grain feeder
Order: Coleoptera
Family: Bostrichidae
Acronym: RDO


  • Adults are dark reddish brown and 3 mm long with distinctly shaped, loose 3-segmented club.
  • Larvae are white and c-shaped. They are immobile at maturity with dark head capsule.

Similar species

Commodities affected

  • Nearly all grains, especially wheat, barley, sorghum and rice
  • Seeds, dried fruit, drugs, cork, wood and paper products

Signs of infestation

  • Large amounts of flour
  • Tunnels and irregularly shaped holes in commodity
  • Sweet odour in the grain


  • Damage is distinctive and heavy
  • Adults and larvae feed on germ and endosperm reducing kernels to shells of bran
  • Adults and larvae also burrow through kernels

How to control

Geographic range

  • Is found worldwide and across Canada, although is not common in all provinces
  • Is not well established in Canada due to colder climate

Where found

  • Is most common in buildings; may be found in shipping containers

Life history

  • Lesser grain borer is one of the most injurious pests known to attack grain.
  • Adults are mobile, able to fly and are long-lived.
  • Females lay eggs one at a time or in batches of up to 30 eggs.
  • Larvae live within the seed and are rarely found in sieve samples.
  • Larvae pupate within grain kernel.


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Video of Lesser grain borer


Adult lesser grain borers move amongst wheat kernels. Some of the insects are inside individual kernels. The kernels have holes that are typical of damage caused by lesser grain borers.