Potentials of Three Plants Leave oils mixture in Protecting Maize Grains against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Abstract

Over the last decade, Sitophilus zeamais are being controlled using synthetic insecticides. The overuse of these chemicals has led to the development of insecticide resistance, environmental pollution, and the killing of non-target organisms. The efficacy of Hyptis suaveolens, Ocimum gratissimum, and Psidium guajava leaf oils combination against adult S. zeamais was investigated on maize grain during the study. The leaves of the plants were grounded into powders, and oils were extracted using a Soxhlet apparatus separately. Maize variety 99% EDVT used was obtained from the International Institute for Tropical Agriculture (IITA) Kano. The insects were cultured in containers and identified using a standard taxonomic key for Sitophilus spp. Different oils combinations of two plant leaf oils were made in the ratio of 50%:50% of the test dose 0.1, 0.2, 0.3, and 0.4ml/20g. Ten newly emerged S. zeamais were introduced separately for examination of adult mortality test and lethal concentration determination. Results showed that mortality increases with exposure period. The leaf oils combination showed a significant difference in adult mortality of S. zeamais (P<0.05). Isobutylcyclohexane, Oleic Acid, and 11-octadecenoic acid were the most occurring compounds present in the individual plant extract. H. suaveolens and O. gratissimum combination protected maize grains against S. zeamais infestation and therefore, the active ingredients of these plant combinations should be evaluated.