Eight common insect pests - Granary weevil

Granary weevil

This weevil is one of the most destructive pests of stored grain worldwide. It is scarce on the Prairies but occurs in Ontario. Granary weevils feed on kernels, leaving only the hulls.

Appearance and behaviour

The adult:

Is about 0.3 to 0.4 centimetres long
Cannot fly
When disturbed, folds its legs under its body and appears to be dead.

Development

Complete development from egg to adult takes about 25 to 35 days under optimal conditions, that is, when the temperature of the grain is 26°C to 30°C and the moisture content is 14 percent.

Weevils develop their life cycle completely inside the grain kernels. It is not until the young adult is formed that it will emerge from the kernel.

The adults have a distinctive snout, with which they bore into grain kernels. The female deposits a single egg in a hole in each kernel and then seals the opening with a gelatinous plug. The larvae feed on the endosperm and complete their development within the kernel. The pupae develop into adults that chew holes in the side of the kernels as they emerge.

Granary weevil image