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Over the last decade, Sitophilus zeamais are being control using synthetic insecticides. The overuse of these chemicals has lead to the development of insecticides resistance, environmental pollution, and 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 Soxhlet apparatus separately. Maize variety 99% EDVT used was obtained from the International Institute for Tropical Agriculture (IITA) Kano. The insects were cultured in a containers and identified using a standard taxonomic key for Sitophilus spp. Different oils combination of two plants leaves 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 leaves oils combination show a significant difference in adult mortality of S. zeamais (P<0.05). Isobutylcyclohexane, Oleic Acid and 11-octadecenoic acid were the most occurring compound present in the individual plant extract. H. suaveolens and O. gratissimum combination protecting maize grains against S. zeamais infestation and therefore, the active ingredient of these plant combinations should be evaluated. Keywords: Gas Chromatography-Mass Spectroscopy (GS-MS), Maize, Mortality, Plant leaves

The insecticidal effects of stem bark powder of Azadirachta indica and leaf powder of Eucalyptus camaldulensis on weevils of stored maize grains was carried out. Four levels: 5.0g, 10.0g, 15.0g and 20.0g of each of the vegetative parts (as treatments) and 0.0g as control were replicated four (4) times, making 36 plots (bottles). These were represented as 36 bottles (kilner jars) each containing 100g of maize, arranged in two separate sets of 16 bottles for each of the vegetative parts. The remaining 4 served as the control, at 0.0g levels. Stem bark powder of Azadirachta indica 5.0, 10.0, 15.0 and 20.0g were introduced into the first set. While the leaf powder of Eucalyptus at 5.0, 10.0, 15.0 and 20.0g were introduced into the second set, followed by vigorous shaking. 30 young adult maize weevils were carefully introduced into each of the bottles and covered with a perforated lid lined with muslin mesh (1.0mm). The bottles and its contents were arranged in a Completely Randomize Design (CRD) for 336 hours (14 days) and 432 hours (18 days) for Eucalyptus and Neem respectively. 10 healthy grains per replicate were sown into polythene pots containing uniform potting mixture of top soil, river sand and cow dung in a ratio of 1:1:1 at the end of the trail. Parameters assessed include mortality, % mortality weight loss, perforation and perforation index (for the insecticidal experiment) and % germination, for the post trail experiments. Result obtained showed a progressive increase in mortality and % mortality, with analysis of variance (ANOVA) not significantly different (P>0.05) at 48 hours after treatment (HAT), but significant (P<0.05) between 96 and 432 HAT. Weight loss, perforation and perforation index were inversely related to the concentrations of the two powder sources, in which cases, the ANOVA of these parameters showed significant different (P<0.05). The % germination obtained did not show much variation despite the significant difference indicated by the ANOVA, thus revealing the preservation potentials of the plant powders.

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