Eucalyptol (1, 8-cineole), a monoterpene oxide with potential for protecting soybean crops against insect pests and phytopathogenic fungi

Abstract Soybean ( Glycine max ), a pivotal global agricultural crop, faces significant economic losses from pests and phytopathogenic fungi. To address this, farmers often resort to synthetic pesticides, posing potential risks to health and the environment. In this context, eucalyptol stands out in agriculture for its toxicity to various insects and fungi, with minimal environmental and human health impacts. This study aimed to i) assess the insecticidal activity of eucalyptol against Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae) and Epicauta atomaria Germar (Coleoptera: Meloidae), and its fungicidal activity against Cercospora kikuchii , Cercospora sojina , and Sclerotium rolfsii ; and ii) explore the potential phytotoxic effect of eucalyptol on non-target soybean plants. Eucalyptol demonstrated good fumigant insecticidal activity against S. frugiperda 1st instar larvae (LC 50 = 26.9 µL/L air) and E. atomaria adults (LC 50 = 34.6 µL/L air), along with moderate fungicidal activity against C. kikuchii and C. sojina (mycelial inhibition halo diameters of 6.0 ± 0.0 mm and 10.0 ± 2.5 mm, respectively, at a concentration of 5 µL/disk). Importantly, eucalyptol exhibited no phytotoxic effects on soybeans. Its potential as a biopesticide for soybean crops, replacing synthetic alternatives, shows promise, though further studies are needed.