Laboratory experiments were carried out to investigate the efficacy of botanical insecticidal materials against a major insect pest of stored beans, Acanthoscelides obtectus. The materials employed by small scale farmers to reduce the problem of bean postharvest losses caused by A. obtectus were identified and collected from Dar es Salaam and also from Kimuli and Mabira villages in Kagera region in Tanzania. The materials were: Azadirachta indica; Tephrosia vogelii Hook; Nicotiana tabacum; Vegetation ash; Ocimum gratissimum and Crassocephalum crepidioides. The efficiency and LC50 of the botanical pesticide materials against A. obtectus were not known. Their efficacy against A. obtectus at different doses was therefore 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: A. indica > T. vogelii> N. tabacum > Vegetation ash > O. gratissimum > C. crepidioides. Kruskal-Wallis test indicated significant differences (P< 0.05) 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 and therefore could be used as an insect pest control strategy.

Keywords: Botanical pesticide materials, Acanthoscelides obtectus, Phaseolus vulgaris, beans, pest control, Tanzania