Toxicity of essential oils on cabbage seedpod weevil (Ceutorhynchus obstrictus) and a model parasitoid (Nasonia vitripennis)

Abstract

Plant essential oils are being increasingly studied as a potential environmentally friendly alternative to synthetic insecticides. The insecticidal efficacy of essential oils on the cabbage seedpod weevil ( Ceutorhynchus obstrictus ), an important oilseed rape pest, has not been previously tested. We examined the impact of six essential oils on C . obstrictus via contact with dry residues on leaf and flower surfaces. We also examined the effect of these essential oils on a model non-target parasitoid wasp, Nasonia vitripennis . Exposure to dry residues of cumin ( Cuminum cyminum ) and cinnamon ( Cinnamomum verum ) essential oils (applied to oilseed rape leaves) resulted in significant loss of mortality and immobility in C . obstrictus adults. Treatment with C . cyminum essential oil at 1.5% resulted in 50.71% mortality and 87.3% combined mortality and immobility in C . obstrictus . Cinnamomum verum oil, at 1.5% concentration, resulted in 88.8% mortality and immobility among C . obstrictus 24 h post-treatment. All treatments studied with essential oil dry residues at 0.3% concentration caused high mortality and immobility in N. vitripennis . The greatest mortality and immobility were observed at 0.3% concentration in F . vulgare and C . verum treatments (54 and 53% loss respectively). At 0.1% concentration, F . vulgare and T . vulgaris significantly reduced parasitoids mobility and at 1.5% concentration all essential oils resulted in 100% mortality of N . vitripennis after 3 h. Our study revealed that C . cyminum and C . verum essential oils may have potential in the management of C . obstrictus . However, their impact on non-target organisms, including parasitoids, needs to be studied more thoroughly to determine the potential of essential oil main compounds in integrated pest management.

Topics & Concepts