Fumigation activity of essential oils of Cinnamomum loureirii toward red imported fire ant workers

Synthetic pesticides used to control Solenopsis invicta Buren (Hymenoptera: Formicidae) can negatively affect human and environmental health due to non-target toxicity and long-lasting residues. Plant essential oils may have lower human health impacts and environmental toxicity. They can be an excellent source of pesticides because of their exceptional repellency and insecticidal properties. In this study, we used the fumigation method to study the insecticidal properties of essential oils from the bark and leaves of Cinnamomum loureirii Nees on S. invicta at different concentrations and fumigation time. The fumigation time with C. loureirii essential oils was positively correlated with the knockdown and mortality of S. invicta and negatively correlated with the grasping. The essential oils at 320 µg/cm 3 had a noticeable fumigation effect. The insecticidal effect of the essential oils extracted from C. loureirii leaves was significantly stronger than that from the bark at effective concentrations. Cinnamyl acetate, an abundant component in leaf essential oils, plays a vital role in increasing the insecticidal effect of trans -cinnamaldehyde. The treatment of the mixed trans -cinnamaldehyde and cinnamyl acetate in a 2:1 ratio had the best insecticidal effect (at 50 and 25 µg/cm 3 , respectively) and more apparent electroantennogram change than the individual compounds. Essential oils caused disorganization and shedding of the antennae morphology and receptors that led to the death of S. invicta . This study provides a basis for developing and utilizing cinnamon leaf oil as a new environment-friendly insecticide resource to control S. invicta . Graphical abstract