Ovicidal, larvicidal, and behavioural effects of some plant essential oils on diamondback moth (Lepidoptera: Plutellidae)

Abstract Alternatives to synthetic insecticides are desirable for management of diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), an insect pest of global importance. Many essential oils derived from aromatic plants have demonstrated toxicity and behaviour altering effects on insect pests, and are considered low-risk alternatives to synthetic insecticides. We conducted laboratory experiments to determine the biological activity of several low-cost, commercially available essential oils against P. xylostella. Experiments testing ovicidal effects, larvicidal effects, larval feeding deterrence, and adult oviposition deterrence were done with essential oils derived from Artemisia abrotanum Linnaeus (Asteraceae), balsam fir ( Abies balsamea Linnaeus (Pinaceae)), black pepper ( Piper nigrum Linnaeus (Piperaceae)), eucalyptus ( Eucalyptus polybractea (Baker) (Myrtaceae)), garlic ( Allium sativum Linnaeus (Amaryllidaceae)), rosewood (a blend of different oil constituents), tansy ( Tanacetum vulgare Linnaeus (Asteraceae)), and thyme ( Thymus zygis Linnaeus (Lamiaceae)), using concentrations of 1, 2.5, and 5% v/v. Although all essential oils had some level of bioactivity against certain P. xylostella life stages, essential oils from garlic, rosewood, and thyme were most effective overall, demonstrating significant ovicidal and larvicidal activity, as well as deterrent effects on larval feeding and settling behaviour, and adult oviposition. Although variable phytotoxicity was observed with essential oils at 2.5% and 5% v/v concentrations, the results suggest that rosewood, garlic, and thyme essential oils have potential in management of P. xylostella.