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The lethality of powders made from rice husk (RHP), dry fruits of Piper guineense (PGP), dry flower buds of Eugenia aromatica (EAP) and a diatomaceous earth (SilicoSec) (DE), and some of their mixes to adults of Sitophilus zeamais Motsch., S. granarius L., Lasioderma serricorne F. and Callosobruchus maculatus F. was investigated under controlled conditions of 25° C and 60% relative humidity. The materials were tested singly at 2% of grain weight in glass Petri dishes against 20 adults of each beetle. Adult mortality was observed up to 10 days post treatment. One day post treatment DE produced 100% mortality in L. serricorne and C. maculatus which was significantly higher than mortality recorded in all other treatments. The mortality of L. serricorne (90.0%) and C. maculatus (86.7%) produced by E. aromatica powder was next to DE and was also significantly higher than mortality recorded in other treatments. As from 3 days post treatment DE and E. aromatica powder caused 100% mortality of L. serricorne and C. maculatus adults. DE and E. aromatica also caused 100% mortality of S. zeamais and S. granarius at 10 days post treatment. The adult storage beetles irrespective of species and at all times of observation suffered significantly lower mortality when exposed to grain treated with RHP and PGP. The combinations of EAP and DE (ratios 1:1, 3:1 or 1:3) produced generally higher mortality in S. zeamais and S. granarius than other combinations 3, 5 and 7 days post treatment.  By 10 days post treatment all the EAP/DE and PGP/DE combinations produced 100% mortality of S. zeamais and S. granarius. One day post treatment EAP/DE combinations (ratios 1:1, 3:1 or 1:3) produced significant mortality (100%) in C. maculatus and L. serricorne . Adult mortality in RHP/DE (1:3) (88.3%) and PGP/DE (1:3) (83.3%) involving C. maculatus, and RHP/DE (1:1,1:3) (100%) and PGP/DE (1:1, 1:3) (86.7%, 100%) involving L. serricorne was also significant. By 2 days and 3 days post treatment all mixtures have produced 100% mortality in C. maculatus and L. serricorne adults except RHP/DE (3:1) (75%) and PGP/DE (1:1, 3:1) (80.0%, 78.3%) involving C. maculatus. EAP and DE applied at 0.01, 0.02, 0.03 and 0.04 g/20 g of grain produced 100% mortality of C. maculatus adults. Keywords: Plant powders; diatomaceous earth; lethality; storage beetles ______________________________________________________________________________