Toxicity and repellency of essential oils against the maize weevil Sitophilus zeamais (Motschulsky, 1855) (Coleoptera: Curculionidae)

Usually, Sitophilus zeamais control is carried out through chemical fumigation, which is relatively effective, albeit highly toxic, potentially causing damage to the agroecosystem. In the search for alternative management methods, research on the use of essential oils has increased, as they contain compounds with insecticidal action. The aim of the present study was to verify the effects of some essential oils on S. zeamais. Glass jars were used as fumigation chambers, with a filter paper on the lid, where 20 µL of each essential oil were pipetted. The oils of Piper nigrum, Melaleuca alternifolia, Lavandula officinalis, and Foeniculum vulgare were used. After 24 hours, mortality assessment was conducted by counting the number of dead insects. The repellency test was executed through an arena system with 5 plastic containers arranged equidistantly in a circle. In the central container, 5 adult female S. zeamais were placed in each repetition, and in the others, 20 g of corn were placed in each, with two treated with a 2% essential oil solution in distilled water and Tween 80® and two treated only with distilled water and Tween 80®. After 72 hours, repellency evaluation was performed by counting the number of insects in each container and the percentage of damaged grains. It was observed that the essential oils showed moderate toxicity against S. zeamais; however, they exhibited repellency at the evaluated dose. It is concluded that the tested essential oils have repellent properties against S. zeamais and can be used as a control method.