The silky box tree moth (Cydalima perspectalis) is a butterfly species native to East Asia that is a well-known pest, which is why it attracted the attention of scientists at ELKH's Centre for Agricultural Research. The species was presumably introduced into Europe with propagating material and has conquered the entire continent since its first appearance in Germany in 2007, causing enormous damage to ornamental gardens, arboretums and castle parks. The most severe damage has been seen in Western Europe, but its presence has also hit hard the Caucasus, where the box tree moth is native and an important shrub-level plant species in woodlands.
In the course of their research, the staff at the Plant Protection Institute of ELKH's Centre for Agricultural Research investigated commercially available essential oils in search of potentially repellent compounds. The use of essential oils as insecticides and insect repellents is not new in the history of mankind. Their use is hampered by the fact that they are phytotoxic when sprayed, and due to their composition, which sometimes consists of hundreds of volatile compounds, they evaporate quickly and thus lose their effect. In the experiments, the Institute's researchers tested an emitter with a wick instead of spraying, which releases the measured essential oil into the plant's environment continuously for a long period. All three essential oils included in the experiment — cinnamon, eucalyptus and lavender — reduced the number of butterfly eggs deposited on potted box tree plants compared to untreated plants. Significantly, however, only cinnamon compounds deterred egg-laying females. Volatile detector gas chromatography was then used to determine the volatile compounds in the essential oils that the silky box tree moth can detect – so it has an olfactory receptor tuned to the compound on its tentacles – as these may potentially be responsible for the repellent effect or prevention of egg laying. By limiting the experiments to synthetic variants of these specific compounds, an even more effective deterrent mixture can be developed in the future against silky box tree moths. Along with a pheromone trap for males, repelling females may be a genuine alternative to insecticide treatment.
Szelényi M.O, Erdei A.L., Jósvai J.K., Radványi D., Sümegi B., Vétek G., Molnár B.P. and Kárpáti Zs. (2020): Essential oil headspace volatiles prevent invasive box tree moth (Cydalima perspectalis) oviposition – insights from electrophysiology and behavior. Insects, 11(8), 465, https://doi.org/10.3390/insects11080465