Bruchids

Credits:Biovision-Infonet

Bruchids such as the bean bruchid or dry bean weevil (Acanthoscelides obtectus), and the Mexican bean weevil (Zabrotes subfasciatus) are storage pests, attacking dried beans in Africa. They are small beetles (3-5 mm) grey, brown to reddish-brown in colour. Females of the dry bean weevil lay eggs glued to the bean seeds, while females of the Mexican bean weevil lay eggs scattered between the bean seeds. Development takes place inside the bean and takes about one month before the adult emerges. The larvae feed on the seeds destroying them or reducing germination capacity. The adult emerges from the seeds leaving small round holes on the bean seeds. Heavy infestation can result in a large number of holed seeds, with adults moving across the stored beans. The dry bean weevil can attack pods in the field laying eggs on ripening pods. The Mexican bean weevil attacks only beans in storage.

What to do:

• Bruchids can be controlled through good storage hygiene. Remove infested residues from last season’s harvest.
• When small lots of beans are stored, daily turning of the storage container can significantly reduce infestation.
• Complete control of bruchids can be achieved by coating stored seeds with vegetable oil such as cotton seed or coconut oil (small or medium amounts of grain).
• Farmer experience: Solar drying of bean seeds before storage is essential. Before storage, treat or mix stored seed with a mixture of plant parts (e.g. neem, lantana, pyrethrum and others), vegetable oil (e.g. neem, coconut, castor bean, cottonseed, groundnut, maize, among others) or mineral substances (e.g. sand, diatomite among others). Diatomite is commercially available as Kensil Lagging from most hardware shops in Kenya.
• Pyrethrum (botanical) is effective in controlling weevils.