Selection of an essential oil from Corymbia and Eucalyptus plants against Ascia monuste and its selectivity to two non-target organisms

Due to an increase in environmental and health issues and with the excessive use of synthetic pesticides, many studies are investigating plant essential oils (EOs) for pest control. These compounds are considered safe control agents since they have low toxicity to non-target organisms. Thus, this study aimed to select potential EOs from the Myrtaceae family and their constituents for the control of Ascia monuste (Godart) and to evaluate those EOs selectivity to two non-target organisms (Solenopsis saevissima Smith and Tetragonisca angustula Latreille). Twelve EOs, extracted by hydrodistillation from Corymbia and Eucalyptus plants, were tested in this study. All toxicity bioassays were performed by topical application. C. citriodora EO had the highest insecticidal activity against A. monuste (LD50 = 20.61 μg/mg) and also presented a fast action (LT50 < 10 min). Citronellal was the main compound of C. citriodora EO (86.8% of the oil constitution) and exhibited toxicity similar to this EO. The other compounds caused no significant mortality. Hence, the toxicity of the C. citriodora EO is mostly explained by the citronellal activity. This EO was selective in favor of the predatory ant S. saevissima but caused high mortality of the pollinator bee T. angustula. Therefore, C. citriodora EO is a promising model in the development of insecticides against A. monuste. However, to mitigate its impact over pollinators, its application must rely on the principles of ecological selectivity.