Pesticidal Potentials of Seed Extracts Of Black Pepper (<i>Piper Nigrum</i> L) in the Control of Maize Grain Weevil (<i>Sitophilus Zeamais</i> Mots) in Storage

Abstract

This study was conducted between November 2009 – May 2010 at the Teaching and Research farm of Imo State University, Owerri, Nigeria. Five rates of ethanolic and powder extracts of black pepper, Piper nigrum L were used (0.0, 0.1, 0.2, 0.3, and 0.4) in milliliters and grams as treatments respectively, using Completely Randomized Design (CRD). The parameters determined were mortality rate, grain damage (exit holes), germination percentage, presence of phytochemicals and infrared spectroscopy. Results showed that both ethanolic and powder extracts, killed Sitophilus zeamais but the ethanolic extracts were significant, more effective and quicker in action at P≤ 0.05. However, it was observed that the bio efficacy of the extracts increased with increase in the level of concentration. Ethanolic and powder extracts of P. nigrum L. at 0.4, 0.3 and 0.2mls/g were significantly (P≤ 0.05) more effective in the control of maize grain weevil in storage than 0.1 mls/g within12-48hours and 12-72 intervals respectively. There were no grain damage (exit holes) on treatments with ethanolic extracts but with powder extracts, exit holes were noticed but differed significantly at (P≤ 0.05). On seed germination tested 6 months after treatments, 0.2 and 0.4mls gave the highest number of maize grains with radicule and plumule emergence, 80% each while 0.1 and 0.3mls gave 70% each. None of the treatments was significant at (P< 0.05) except over the control. Phytochemical screening of the plant extract revealed the presence of bio-active compounds comprising alkaloids (50.13 – 8 5.67%), flavonoids (24.56 – 4.02%), Tannins (17.79 – 0.22%), Saponnins (5.51 – 7.52%) and Phenols (2.01 – 0.71) % in decreasing order of percentage. The infrared spectroscopy revealed some functional groups – OH, - COOH radicals and double bond ketones. These compounds have the implication of exerting different toxicities on organisms.

Keywords: P. nigrum, S. zeamais, Maize, Phytochemical, Pesticidal Potentials