Granary weevil

Systematic position: The granary weevil (Sitophilus granarius) is a member of the order Coleoptera and the family Curculionidae. It is considered one of the most destructive pests of stored grain products globally, having adapted to live and reproduce exclusively within stored grain environments such as silos and warehouses.

Affected crops: This pest primarily targets whole kernels of various cereal crops. Its preferred food sources include wheat, rye, barley, corn, rice, and oats. In addition to raw grains, it can occasionally infest pasta, flour, and other processed grain-based products stored in warehouses for long periods.

Biology and life cycle: Adult weevils are flightless and spend their entire lives in or near the grain mass. A female bores a small hole in a kernel, deposits a single egg, and seals it with a gelatinous substance. The larvae develop entirely inside the grain, consuming the endosperm. The entire life cycle, from egg to adult, takes approximately 30 to 60 days depending on temperature and moisture levels.

Nature of damage and economic impact: The damage is primarily caused by the larvae, which hollow out the grain kernel. This leads to substantial weight loss, reduced nutritional value, and total loss of germination capacity in seed grain. Heavily infested grain masses often experience increased moisture and heat, which promotes the growth of harmful molds and encourages secondary pest infestations.

Key management and control strategies:

• Rigorous cleaning and disinfection of storage facilities before harvest arrival.
• Drying grain to a moisture content below 13% to inhibit pest development.
• Fumigation of infested grain lots using approved chemical agents to kill all life stages.
• Cooling stored grain through aeration to slow down the metabolic activity of insects.
• Regular monitoring and sampling of stored grains to detect early signs of infestation.