COMPARATIVE BIO-ACTIVITY OF SOME EDIBLE SPICE POWDERS IN THE CONTROL OF THE MAIZE STORAGE WEEVIL (Sitophilus zeamais Motsch)

Five edible plant product powders (EPPP), West African black pepper (WABP) (Piper guineense Schum and Thonn.), clove (Syzgium aromaticum (L.) Merril & Percy), Ethiopian pepper (Xylopia aethiopica (Dunn) A. Rich), Alligator pepper (Aframomum melegueta Schum) and ginger (Zingiber officinale Rosc.), were studied for their acute toxicity and effectiveness in repelling, acute toxicity, oviposition and progeny emergence suppression of Sitophilus zeamais (Motsch) activities at the rate of 0.5, 1.0, 1.5 and 2.0 g/10g maize seeds. The experiment was carried out as treatments before infestation (TBI) and treatment after infestation (TAI), in the laboratory under ambient temperature and relative humidity. All the dosage rates tested evoked repellency class of III and IV in all the (EPPP) treatments, while the control evoked class II. The results of the acute toxicity showed that all the EPPP can cause mortality of S. zeamais albeit at low dosage rates. Thus, the EPPP can be ranked in order of toxicity as WABP > Clove > Ginger > Alligator pepper > Ethiopian pepper. All the plant product powders significantly (P< 0.05) reduced oviposition by S. zeamais when tested as treatment before infestation, compared with control treatments. P. guineense and S. aromaticum at all dosage rates completely inhibited progeny emergence. The activities of A. melegueta, X. aethiopica and Z. officinale were dose dependant in reducing progeny emergence (P< 0.05). In the case of treatment after infestation progeny, emergence was least in treatments with WABP, clove and Ethiopian pepper. There were however, significant differences (P<0.05) between the EPPP and the control treatment at all dosage rates. The potential effectiveness of all the EPPP implies that stored maize could be adequately protected against S. zeamais thus reducing infestation.