The Essential Oils Compounds of Lippia multiflora Moldenke and Cymbopogon schoenanthus (L.) Spreng Repel and Affect the Survival of the Maize Pest Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae

Plant-derived insecticides, such as essential oils, can be an effective alternative to replace synthetic chemical insecticides against Spodoptera frugiperda, which becomes increasingly resistant to synthetic products. This study aims to evaluate essential oils (EOs) effects on larval growth and development following feeding inhibition, growth regulation, and repellency of EOs of Lippia multiflora (Verbenaceae), Cymbopogon schoenanthus (Poaceae), and their combination. Topical application of EOs was used on S. frugiperda larvae for larvicidal effect or treating filter paper with the EOs to find repellency. The effect of EOs on food intake and larval growth was also evaluated. Several types of compounds have been identified in the EOs, mainly monoterpenes with the appearance of new compounds in the 1 : 1 combination. Bioassay results show that individuals and combinations of EOs significantly influenced S. frugiperda larval development. L. multiflora caused 100% mortality of L2 larvae within 24 hours at 3%. The Lm + Cs (1 : 1) EOs combination was the most effective with LC50 and LC90 of 1.02% and 1.92%, respectively. Lm + Cs (1/4 : 3/4) EOs caused the highest inhibition of food consumption, 0.0160 g consumed after food was treated with 2.2% concentration compared to food consumption of 0.0602 g for the control group at 24 hours. Lower food consumption caused the inhibition of larval growth and weight loss of 0.0005 g/day at the 2.2% EOs concentration. The highest repellency effect of the EOs was found in EOs of L. multiflora, exhibiting a repulsion of 83.33% of the larvae after 3 hours of exposure. This diversity in the biological actions of the EOs tested on S. frugiperda represents valuable options for contributing to integrated pest management and an alternative to synthetic chemical insecticides.