Laboratory Assessment of the Levels of Resistance in Some Bean Varieties Infested with Bean Weevils (Acanthoscelides obtectus and Zabrotes subfasciatus)

The main objective of the study was to assess levels of resistance of some selected bean (Phaseolus vulgarisL.) varieties to storage bruchids (Common bean weevil Acanthoscelides obtectus (Say) and Mexican weevil Zabrotes subfasciatus). Specifically it aimed at determining bruchids emergence and median development period, finding out the extent of damage caused by the bruchids on each variety and determining the weight loss incurred by each variety due to bruchids infestation. The experiment was laid out in a Complete Randomized Design (CRD) with four replicates. The study was conducted at Bunda college of Agriculture-Department of Crop and Soil Sciences-Entomology Laboratory. It was conducted from September 2012 to January 2013. Seven bean varieties, Kalima, Nasaka, BCB3, Sapelekedwa, BCB1, Bwenzilaana, and BCB2 were used as test materials. 100 g of bean seeds sample from each variety were put in kilner jars and were infested with 16 bruchids of common weevil and Mexican weevil, and it was carried in two phase; the first phase was used collect data for emerging insects and median development period; and Second phase was used to collect other data parameters. The results at P=.05 only BCB2 was found to be significantly resistant to storage bruchids, Sapelekedwa was the only moderate resistant, Nasaka, BCB3 and Kalima were susceptible and finally Bwenzilaana and BCB1 were highly susceptible. The results also showed that the damage caused by the storage bruchids ranged from 20% in resistant varieties to 88% in high susceptible varieties while the weight loss ranged from 3% to 29%. It was concluded that the level of resistance among the seven varieties evaluated to two common bean weevils (Acanthoscelides obtectus and Zabrotes subfasciatus) differed significantly during the four and half month’s storage period.