Salicylic Acid as a Modulator of Insect Interactions in Tomato Crops

Salicylic acid (SA) is a key regulator of plant defense signaling and is widely used as a plant defense inducer in crop protection. However, its effects on insect host-selection behavior and plant chemical signaling remain incompletely understood. Here, we evaluated how exogenous SA application affects tomato-insect interactions by examining behavioral responses of two major pests, Tuta absoluta (Lepidoptera: Gelechiidae) and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), together with changes in plant volatile emissions. Tomato plants were sprayed with SA and tested in preference bioassays and Y-tube olfactometer assays, while volatile profiles were analyzed by GC-MS. SA treatment significantly altered the volatile profile of tomato plants and increased the attraction of both insect species in olfactometer assays. However, these responses did not translate into consistent host acceptance: T. absoluta females tended to lay more eggs on SA-treated plants, whereas T. vaporariorum adults tended to settle on untreated plants. Several volatiles that changed after SA application, including 1-octen-3-ol, γ-terpinene, (E)-caryophyllene and α-humulene, have previously been reported to be detected by T. absoluta antennae and may contribute to host-location cues. Together, these findings indicate that SA-induced changes in tomato volatile emissions can modify herbivore attraction, but subsequent host acceptance responses depend on species-specific behavioral mechanisms. These results highlight the complexity of plant defense induction and its potential consequences for pest management strategies. Specifically, our findings suggest that while SA application may contribute to reducing whitefly settlement, it could simultaneously increase the susceptibility of tomato plants to T. absoluta infestation.