Efficacy of Piper guineense (Schum & Thonn) seed extract against maize weevil, Sitophilus zeamais (Motschulsky) as influenced by different extraction solvents

Abstract The seed extract of black pepper Piper guineense Schum & Thonn was evaluated for its biological activity against the maize weevil Sitophilus zeamais Motschulsky at 30°C, 65 ± 2% R.H and 12:12-h light:dark regimes in the laboratory. The different solvents used for the extraction were acetone, ethanol, n-hexane, petroleum ether (60:80) and distilled water at 0.3% dosage level. The acetone extract had the highest toxicity (100%), while the control showed no toxicity at 28 days post treatment. All of the treatments significantly reduced adult emergence and grain damage compared with the control. Grain germination with the solvents was significantly higher than with the aqueous extract (49%), which was significantly superior to the control (39%). Piper guineense extract with the different organic solvents caused acute mortality in S. zeamais adults.