Tuesday, October 25, 2016

Grain weevil: Sitophilus granarius

Sitophilus granarius is a grain weevil, and is largely restricted to temperate regions, including cool highland areas in tropical latitudes. The Anglo-Saxon word wifel, from which weevil is derived referred to the grains weevil, which has infested stored grain since prehistoric times.

The adults and larvae of this weevil will feed in grain and cereal products, but it is primarily a pest of whole grain. It breeds in chickpeas, and all common grains such as maize, oats, barley, rye, wheat, kafir, buckwheat and millet. The egg is laid and the larva lives inside cereal grains, hollowing them out and causing serious damage if uncontrolled.

It can be destroyed by fumigation in suitably constructed storehouses.It also infests many foodstuffs prepared from flour. This weevil was a huge problem in the days of sailing ships because the staple food on board was a thick, hard cookie in which the grain weevil thrived.

Some sailors broke their cookies and tapped them on the table to dislodge the grubs and beetles; others ate them as they were and were possibly better nourished as a result.

The Sitophilus granarius can be recognized by the presence of a prominent snout at the front of the head. Adult are 2.5 – 45 mm long, dark brown to blackish brown, and without pale markings on the elytra. Pronotum has punctures that are distinctly elongate or oval and not round or irregular-shaped, as in S. oryzae and S. zeamais.

Eggs are laid inside grain of cereal and the larva remains in the grain, feeding and pupating, before the adult emerges through a small exit hole. This activity produces large quantities of dust and faecal material known as ‘frass’ and may cause significant economic loss.

Infestation can go in detected for a period of time, and can be introduced into new areas when grain is moved.
Grain weevil: Sitophilus granarius
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