Comparative efficacy of extracts from Azadirachta indica, Piper guineense and pirimiphos-methyl against Sitophilus zeamais Motschulsky (Coleoptera : Curculionidae) in stored maize

Abstract

Efficacy of ethanol seed extracts of Azadirachta indica A. Juss and Piper guineense Schum and Thonn at concentrations of 10, 20, 30 and 40 %v/v, each as proctectant in the control of the maize weevil, Sitophilus zeamais, were compared with a conventional insecticide, pirimiphos-methyl at a rate of 0.5 ml / 50 g maize grains of Oba Super II variety. Experiment was carried out in the Entomology Research Laboratory, University of Ibadan under laboratory conditions of 27 ± 2?C ambient temperature and 65 ± 5% relative humidity and was arranged in a Completely Randomised Design in four replicates. Parameters assessed, including adult mortality, rate of adult emergence, grain damage and weight loss and seed viability, were subjected to analysis of variance and means separated using Duncan’s Multiple Range Test. Mortality of adult S. zeamais increased with increasing concentration of the extracts as well as with days of exposure. All the treatments were better than the control (P < 0.05) in reducing the number of emerged adult S. zeamais and grain damage. P. guineense at 30 and 40 %v/v competed with pirimiphos methyl in the parameters so examined. There were no significant differences (P > 0.05) in the mean percentage germination of the maize seeds in all the treatments.

Keywords: Azadirachta indica, Piper guineense, pirimiphos-methyl, Sitophilus zeamais