Bean weevil

Taxonomy. The bean weevil (Acanthoscelides obtectus) belongs to the order Coleoptera and the family Bruchidae. It is considered a cosmopolitan pest of great economic importance, capable of causing devastating losses in both field-grown bean crops and stored legumes.

Host crops. The primary host for this pest is the common bean (Phaseolus vulgaris). However, it is also known to infest a variety of other pulses, including cowpeas, chickpeas, lentils, and peas. Its ability to complete its entire life cycle inside the seed makes it a primary threat to international trade and agricultural sustainability.

Biology and life cycle. Adults are small, oval-shaped beetles measuring 3–4 mm in length. A female lays eggs on the surface of bean pods or inside cracks in stored seeds. Upon hatching, the larvae burrow into the seed to feed on the embryo and cotyledons. Depending on ambient temperatures, the weevil can produce multiple generations per year within storage facilities.

Damage and economic impact. The infestation is characterized by circular exit holes created by emerging adults. Larvae consume the inner portion of the seed, drastically reducing the weight, nutritional value, and seed germination potential. Severe infestations often result in the complete destruction of stored pulses, making them unfit for consumption or planting.

• Harvesting beans promptly to prevent initial infestation in the field.
• Drying harvested seeds thoroughly to lower internal moisture levels.
• Cleaning storage facilities meticulously to remove potential refuges.
• Using cold storage or heat treatment to eliminate larvae within the seeds.
• Applying authorized insecticides or fumigants for larger grain storage quantities.