Dose-dependent effect of methyl jasmonate on <i>Drosophila suzukii</i> (Matsumura) (Diptera: Drosophilidae)

<i>Drosophila suzukii</i> is a significant pest of soft- and thin-skinned fruit crops. Synthetic pesticides remain the primary control method; however, their use raises concerns about insect resistance and harmful pesticide residues in produce. Methyl jasmonate (MeJA), a plant growth regulator in the jasmonate family, plays a key role in plant defence against herbivores and has been identified as a repellent for arthropods of medical and veterinary relevance. This study examined the effect of MeJA on <i>D. suzukii</i> female oviposition and adult behaviour using two-choice bioassays. In a two-choice cage, doses above 1287.5 µg/filter paper deterred <i>D. suzukii</i> females from oviposition by more than 90% on artificial fruits. Using a two-choice planar olfactometer, MeJA also repelled both sexes with median repellent dose (RD₅₀) values of 55.24 µg/filter paper for females, 55.03 µg/filter paper for males, and 55.14 µg/filter paper for total adults. Interestingly, MeJA demonstrated a dose-dependent dual effect: at 309.0 µg/filter paper, it functioned as a bio-repellent, while lower doses (3.86-15.45 µg/filter paper) acted as an attractant. This dual effect suggests that MeJA could serve as both a repellent and an attractant depending on its dose, with potential applications as a lure in traps.