Chemical diversity of essential oils of Myrtaceae species and their insecticidal activity against Rhyzopertha dominica

Abstract

Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) is one of the main stored grain pests in the world. The present study describes the investigation of the insecticidal activity of essential oils (EOs) extracted from the leaves of twelve Myrtaceae species against this important pest. The essential oils of Eucalyptus resinifera Sm. (Myrtaceae) were the most actives and presented 1,8-cineole (59.3%), p-cymene (12.9%), and α-pinene (9.7%) as the main components. Contact bioassays revealed that the EOs of E. resinifera were less toxic (LD50 = 17.08 μg mg−1 of insect body weight; LD95 = 56.17 μg mg−1) than the commercial insecticide pirimiphos-methyl (LD50 = 0.49 μg mg−1; LD95 = 1.14 μg mg−1) used as positive control. In the fumigation bioassays, however, these EOs were more effective (LC50 = 70.55 μL L−1, LC95 = 266.40 μL L−1) than the commercial insecticide (LC50 = 154.74 μL L−1; LC95 = 334.95 μL L−1). The LT50 on R. dominica adults for the EOs of E. resinifera were 1.75 h and 13.0 h in the contact and fumigation bioassays, respectively. The fumigant effect was due to the terpenoid 1,8-cineole, while the contact effect was caused by the association of the major components of the essential oils of E. resinifera. Thus, the EOs of E. resinifera have potential to be used as an alternative to commercial insecticides in R. dominica management.