Biological assays were carried out to determine the effectiveness of powders of three locally available plants, Dennettia tripetala (G. Backer), Xylopia aethiopica (A. Rich) and Aframomum melegueta (K. Schum), for the control of Cylas puncticollis a sweet potato weevil. Powders of the leaves and fruits of each plant were separately applied at concentrations of 1, 3 and 5% (w/w for powders) for biological assays. This was laid out in a completely randomised design with each treatment replicated four times. Results revealed that 3 and 5%powders of the three test plants led to significantly (P < 0.05) higher mortality of C. puncticollis as compared to 1 % (powders) and the control (0.0 for powder). The fruit powders were more effective than leaves. The effectiveness of these plant products on C. puncticollis was directly proportional to concentration, with higher concentration providing greater protection of the tubers. Powders of A. melegueta and X. aethiopica fruits at 5 % applications caused the highest significant mortality of C. puncticollis after 96 h.Adult emergence was also significantly higher in the control than in treated tubers with A. melegueta giving the lowest number of emerged adults. Quantitative analysis of the plant products revealed the presence of the active phytochemicals (alkaloids, flavonoids, tannins, saponins, steroids, carotenoids and phenols) in various proportions, which may have caused the mortality of the pest in question on sweet potato in post-harvest storage at a small scale in Calabar, Nigeria.