Grain mite

Acarus siro (L.)


Secondary pest; Grain and fungal feeder
Order: Acarina
Family: Acaridae
Acronym: ACA


  • Mites are white and very small (less than 1 mm in length).
  • Mites are soft bodied and have only a single body part.
  • Nymphs have 6 legs and adults have 8 legs.


Similar species

  • Many species of mites, some predatory, are easily confused with grain mites.
  • Some psocids are similar in size, but differ in body structure.

Commodities affected

  • Flour, grain, seeds and bulbs
  • Also fungi that develop on these products

Signs of infestation

  • Grain dust may appear to be moving, actually mites are moving.
  • Very high mite populations cause a sweet odour.


  • Germ of grain is often completely destroyed
  • Food may be rendered unusable for consumption

How to control

Geographic range

  • Is found worldwide and across Canada

Life history

  • Females may lay up to 250 eggs in a month.
  • Some mites may also enter a highly resistant, non-feeding resting stage known as a hypopus.
  • Mites thrive in high humidity conditions.
  • Mites mainly feed on the germ.
  • Mites can subsist on organic debris in cracks, crevices and corners of storage areas.


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