Insecticidal and Repellent Activities of Four Essential Oils Against Sitophilus zeamais (Coleoptera: Curculionidae).

Objective: This study aimed to evaluate the efficacy of Corymbia citriodora, Melaleuca alternifolia (Myrtaceae), Mentha × piperita (Lamiaceae), and Schinus terebinthifolius (Anacardiaceae) essential oils as an alternative to manage Sitophilus zeamais (Coleoptera: Curculionidae) adults.

Methods: Acute contact toxicity, acute toxicity on treated maize grain, fumigation toxicity, repellency bioassays, and GC-MS analysis of the essential oils were carried out.

Results: Corymbia citriodora, M. alternifolia, M. × piperita, and S. terebinthifolius oils were toxic at different levels to S. zeamais through residual contact, ingestion and via fumigation, and were also repellent to adults of this pest. Melaleuca alternifolia oil was the most active in contact (LC₅₀ = 18.98 μL.mL^-1), ingestion (LC₅₀ = 1.03 μL.g^-1), and fumigant (LC₅₀ = 20.05 μL.L^-1 air) bioassays. Citronelal (53.6% in C. citriodora), terpinen-4-ol (46.9% in M. alternifolia), menthol (44.8% in M. × piperita), and β-caryophyllene (16.2% in S terebinthifolius) are the major constituents of these oils.

Conclusions: Melaleuca alternifolia and M. × piperita essential oils can be used by residual contact, while those of C. citriodora, M. alternifolia, and M. × piperita by mixing with maize grains. Melaleuca alternifolia essential oil can be used as a fumigant, while those of C. citriodora and S. terebinthifolius as repellents for S. zeamais adults.