Sitophilus granarius (L.)
Primary pest; grain feeder
- Adults are uniformly coloured dark brown beetles, about 5 mm in length.
- Adults are unable to fly.
- Larvae are white, legless grubs that develop within the kernel and, as such, will not be detected in sieve samples or Berlese funnel samples.
- All small grains (notably wheat, corn, rye, oats, barley, sorghum)
- Sometimes found in pasta, flour, meal and other cereals but is generally unable to breed in this environment
Signs of infestation
- Increased moisture levels and heating on the surface
- Seeds with round holes formed by exiting adults
- Adults feed on whole seeds or flour.
- Larvae develop inside seeds or pieces of seed or cereal products large enough to house larvae, but will not develop in flour unless it has been compacted.
- Weevils can achieve almost complete destruction at high densities.
- Feeding contributes to heating and infested grain is often damp due to moisture added by the insects’ metabolic processes.
How to control
- Is distributed worldwide.
- In Canada, it is found in British Columbia, Alberta, Saskatchewan, Manitoba and is common in farm storage in southern Ontario.
- Only occurs where grain is stored; does not breed in field
- Females lay 150 eggs over their 7 to 8-month lifespan.
- Females individually lay eggs within kernels.
- Adults emerge from a large, oblong hole in kernel, compared to a smaller and rounder hole for rice weevil.
- Infestation can establish at temperatures as low as 15oC, but development is prolonged.
- Optimum development takes place between 26 to 30oC at a relative humidity of 70%.
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