Potency of Traditional Insecticide Materials against Stored Bean Weevil, Acanthoscelides Obtectus (Coleoptera: Bruchidae) in Tanzania

Abstract

The bean weevil, Acanthoscelides obtectus is a major insect pest of stored common bean, Phaseolus vulgaris an important source of plant protein in many parts of the world, Tanzania inclusive. In rural Tanzania, most smallholder farmers apply traditional insecticide materials in the protection of bean from insect pests. The laboratory study investigates the potency of the selected traditional insecticide materials employed by small scale farmers to reduce stored bean losses caused by A. obtectus. The materials were identified and collected from Kimuli and Mabira villages in Kagera region and from Dar es Salaam. The effect of the materials to A. obtectus at different doses and durations was determined by both the number of surviving insects in treated set-ups reflecting the insect mortality and by the insects' reproductive performance at first filial generation (F1). The findings revealed effectiveness of the materials against A. obtectus to vary in the order: Azadirachta indica > Tephrosia vogelii> Nicotiana tabacum > Vegetation ash > Ocimum gratissimum > Crassocephalum crepidioides. Kruskal-Wallis test indicated significant differences in the number of A. obtectus survivors among the treatments at different doses during the study periods and also in the number of insects’ progeny (F1) produced at the end of their life cycle. It was concluded that the materials exhibit potency against A. obtectus at varying levels.

Keywords: Traditional insecticide materials, Acanthoscelides obtectus, potency, Phaseolus vulgaris, mortality