LAUSR

Our study examined the repellent and toxic effects of ethanolic extracts from Mentha haplocalyx and Allium ascalonicum against adult and larval forms of maize weevil, Sitophilus zeamais, at 25 ± 2 °C with 50±5% relative humidity (RH) and 14L:10D h light-dark cycles in the laboratory. Filter paper discs, 9 cm diameter, were used for area preference testing to determine repellency. One-half of the filter paper was treated with 0.1 ml of essential oil, while the other half was treated with a control solution. Twenty weevil adults were released into each Petri dish on the filter paper and covered with a lid. The experiment was repeated with weevil larvae. Repellency was recorded at 6, 12, 24, and 48 h of exposure. Mentha haplocalyx repellency to adults (67.50 %) and larvae (67.50 %) was higher than A. ascalonicum repellency to adults (66.25 %) and larvae (63.75 %). For toxicity testing, 0.1 ml of essential oil was applied on filter paper discs, 6-cm diameter, and papers were placed inside the lids of 100-ml jars. The lids were placed on jars after weevil adults were added. The test was repeated with weevil larvae. Fumigant toxicity was recorded at 4, 8, 12, and 16 h of exposure. Mentha haplocalyx toxicity to adults (37.34 %) was higher than A. ascalonicum toxicity to adults (26.35 %), whereas A. ascalonicum toxicity to larvae (50.29 %) was higher than M. haplocalyx toxicity to larvae (46.36 %). The chemical components of the essential oils were identified using gas chromatography–mass spectrometry (GC-MS). Bioactivity was higher for M. haplocalyx than A. ascalonicum. Further study is recommended on the bioactivity of individual chemical components of essential oils on S. zeamais and other insect and non-insect pests of stored grains.