Clove-derived eugenol induces strong avoidance behaviour in the invasive fruit fly, Drosophila suzukii
The success of invasive species often relies on sensory adaptations that allow them to exploit new environments. Unlike most of its relatives, the spotted-wing drosophila (Drosophila suzukii) lays eggs in ripening fruit, making it a serious and rapidly spreading agricultural pest worldwide. Spice plants produce volatiles that repel many insects, making them a potential source of D. suzukii behavioural modulators. Here, we examined whether volatiles from clove (Syzygium aromaticum) could alter the behaviour and fitness of D. suzukii. Behavioural assays revealed strong aversion: adults avoided grapes treated with clove extract, while gravid females laid significantly fewer eggs on treated fruit in both no-choice and choice assays. Clove exposure adversely impacted fitness, resulting in slower larval growth, reduced adult weight, decreased emergence rate, and shortened lifespan. Gas Chromatography-mass spectrometry analyses identified eugenol as the predominant volatile. Consistent with this, synthetic eugenol elicited strong avoidance not only in grapes but also across various host fruits, including apple, banana, blueberry, guava, mango, orange, papaya, raspberry, strawberry, and tomato. Furthermore, molecular docking and single-sensillum recordings indicated that eugenol binds most strongly to DsuzOR88a, followed by DsuzOR69a and DsuzOR23a odorant receptors. Subsequently, cheminformatic screening of 1,000 eugenol analogues revealed several structural variants predicted to interact strongly with OR88a, offering additional candidate repellents. By combining behavioural, analytical chemistry, electrophysiological, and cheminformatic approaches, our study demonstrates that clove, through its major volatile eugenol, disrupts host use and reduces fitness in D. suzukii. These results highlight the ecological role of plant-derived repellents in insect-plant interactions and position eugenol as a promising natural compound for sustainable fruit pest management.