Toxicity, repellency and chemical composition of essential oils from Cymbopogon species against red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

The red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is one of the major destructive pests to stored milled products. It has developed resistance to chemical fumigants. Therefore, finding an eco-friendly biofumigant for the management of the pest is of great importance. The main aim of this study was to evaluate the insecticidal efficacy of essential oil from Cymbopogon flexuosus (lemongrass), Cymbopogon winterianus (citronella), and Cymbopogon martini (palmarosa) against T. castaneum and its chemical composition. GC–MS analysis was conducted and results showed that the essential oils of C. flexuosus, C. winterianus and C. martini are rich in citral, neral, cironellol, D-lemonene, geraniol and geranyl acetate respectively. The essential oils from C. flexuosus, C. winterianus and C. martini had a very strong repellent activity to adults of T. castaneum and were significantly repellent at 1.41 µL/cm2. The essential oil of C. flexuosus had a high fumigant activity against adults of T. castaneum with LC50 values of 27.1 and 4.23 µL/L after 24 and 48 h exposure. Furthermore, essential oils of C. winterianus had a high contact toxicity to T. castaneum with LD50 values of 2.1 and 1.5 µg/L after 24 and 48 h exposure, followed by 2.5 and 1.6 µg/L of C. martini and 4.09 and 2.07 µg/L of C. flexuosus after 24 and 48 h exposure respectively. The results show that essential oils extracted from the Cymbopogon species are natural insecticides and can be used as an efficient management tool against T. castaneum.