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Conrad Bérubé |
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Granary Weevil
family: curculionidae
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Granary Weevil Sitophilus granarius (L.) The granary weevil, which is found throughout the world, attacks all small grains and hard cereal products such as macaroni. In Canada, it is somearial found in prairie grain elevators, but is more common in farm storage areas in southern Ontario.
The insects feed on the kernels, leaving only the hulls, and a severe infestation can reduce stored grain to a mass of hulls and frass. They often prepare the way for other insect species that feed on damaged kernels but are unable to penetrate sound grain. In addition, the feeding weevils contribute to grain heating and further damage.
Life History: The adult is a polished chestnut brown or blackish beetle about 5 mm long, with a head that is prolonged into a long, slender snout. The adults, which are unable to fly, live for 7 to 8 months and during this period each female lays about 150 eggs. In egg-laying, the female drills a small hole in the kernel, deposits an egg in the cavity and seals the hole with a gelatinous secretion. There is only one larva in each infested kernel. The white, legless grub completes its growth, pupates and develops into an adult weevil within the kernel. After reaching the adult stage, it eats its way out of the kernel. In summer, the life cycle may be completed in 4 weeks. Infestation can start at temperatures as low as 15 degrees but optimum development takes place at about 30 degrees and at a relative humidity of 70%.
Granary
weevils can spread in grain residues. Because most of the insect's
life cycle occurs inside the kernel, an initial infestation is
difficult to detect. A heavy infestation can be treated with
an approved fumigant or, in winter by cooling the grain to a
temperature of -7 degrees and holding this temperature for at
least 6 weeks. Consult your provincial agricultural representative
for full details on controlling the pest. |
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