Abstract
Plant-derived products can play an important role in pest management programs. Essential oils from Lavandula angustifolia (lavender) and Thymus vulgaris (thyme) and their main constituents, linalool and thymol, respectively, were evaluated for insecticidal activity and synergistic action in combination with insecticides against green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). The essential oils and their main constituents exerted similar insecticidal activity when aphids were exposed by direct sprays, but were non-toxic by exposure to treated leaf discs. In synergism experiments, the toxicity of imidacloprid was synergized 16- to 20-fold by L. angustifolia and T. vulgaris essential oils, but far less synergism occurred with linalool and thymol, indicating that secondary constituents of the oils were probably responsible for the observed synergism. In contrast to results with imidacloprid, the insecticidal activity of spirotetramat was antagonized by L. angustifolia and T. vulgaris essential oils, and linalool and thymol. Our results demonstrate the potential of plant essential oils as synergists of insecticides, but show that antagonistic action against certain insecticides may occur.
Highlights
Synthetic chemical insecticides have been instrumental in the evolution of modern agriculture
Eight essential oils (EOs) compounds isolated from L. angustifolia were detected and quantifiable, >92% of which consisted of linalool and linalyl acetate
We demonstrated that low amounts of readily available EOs can result in significant synergism of a widely used insecticide
Summary
Synthetic chemical insecticides have been instrumental in the evolution of modern agriculture. Overuse and misuse of pesticides has sometimes resulted in problems of environmental contamination, poisoning, pesticide resistance, and pest resurgence. These issues, consumer demands for low-risk products, and legislative withdrawal of older chemistries in many jurisdictions has resulted in increased attention towards reduced-risk tactics for pest management. “Biopesticides” are reduced-risk pesticides usually classified as formulated microbial pathogens or plant derived biochemicals with activity against pest species [1]. An increasingly studied subset of biopesticides are plant essential oils (EOs) [2,3].
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