Chemical composition and insecticidal activity of the essential oils of Foeniculum vulgare Mill., Ocimum basilicum L., Eucalyptus staigeriana F. Muell. ex Bailey, Eucalyptus citriodora Hook and Ocimum gratissimum L. and their major components on Spodoptera frugiperda (Lepidoptera: Noctuidae).
The fall armyworm causes damage at several stages of the maize crop. Due to increasing resistance to synthetic insecticides the use of other techniques for its control has been growing. The aim of this research was to evaluate the chemical composition and insecticidal activity of the essential oils of Foeniculum vulgare, Ocimum basilicum, Eucalyptus staigeriana, Eucalyptus citriodora, Ocimum gratissimum as well as the effect of their major compounds limonene, trans-anethole, citronellal and linalool on the mortality of Spodoptera frugiperda. The essential oils were obtained by the hydrodistillation technique and the major compounds were purchased from Sigma-Aldrich®. Topical contact tests were conducted in 3rd instar larvae for the essential oil, their major compounds and for the control with acetone. The results of the essential oils chromatographic analysis demonstrated a diversity in their chemical constitution, but the most common compounds among them were limonene, trans-anethole and methyl chavicol. All the tested essential oils and their major compounds presented some insecticidal activity. The highest activity was obtained for trans-anethole with a LD50 of 0.027 mg/g of insect, with a toxicity ratio of 1194.07, followed by the oils that exhibited this substance in their chemical constitutions, demonstrating to be an effective and promising alternative in the management of this pest.