Abstract: Plant powders from the seeds of Piper guineense and Monodora myristica were separately applied at different dosages of 1, 5 and 10% (w/w) on stored maize grains and tested against the maize weevil, Sitophilus zeamais in the laboratory for 12 weeks. Parameters assessed were adult mortality at 24, 48 and 72 h, adult emergence and adult weight. The results showed that 5 and 10% powders of both plants were significantly more toxic to S. zeamais and suppressed F1 progeny emergence compared to 1% powders and the controls. However, the mean weight of the emerged adults was not significantly influenced by any of the treatments. The efficacy of the powders on the weevils was dose-dependent with higher doses providing greater protection of the maize grains. This research provides the scientific basis for the potential use of P. guineense and M. myristica powders in stored-product protection at the small-scale farmer level to reduce the application of toxic synthetic insecticides.