Insecticidal and fungicidal activity of Cymbopogon citratus (Poaceae) essential oil on Atta sexdens colonies

Leafcutter ants are one of the most destructive and economically important herbivores in both forest and agricultural crops, due to their abundance and wide distribution. The most used method for controlling this pest is still through synthetic formicides, due to their high efficiency. However, essential oils represent an alternative, as they are biodegradable and selective and have a toxic effect on a wide range of organisms, including leafcutter ants. The combination of insecticidal activity of a product and possible fungicidal activity constitutes an effective strategy against these insect pests, since both agents of this mutualistic interaction (both organisms are benefited) are affected, ensuring quicker collapse of the colony. The aim of this study was to evaluate the insecticidal and fungicidal activity of Cymbopogon citratus essential oil applied on Atta sexdens colonies under laboratory conditions. A nebulized spray system with three concentrations (15, 30 and 60%) and a control treatment were used to evaluate the effect of C. citratus on A. sexdens colonies. The C. citratus essential oils showed both insecticidal activity against the leafcutter ants (A. sexdens) and fungicidal activity against their symbiotic fungi. Colonies exposed to this essential oil showed considerable reduction in the weight of fungal mass, and mortality of both the queen and worker ants, which proves to be promising for the development of new insecticides for management of this insect pest.