Effectiveness of Multi-Component Kairomones for Trapping Popillia japonica in Italy

Popillia japonica is an invasive, highly polyphagous scarab beetle causing substantial economic and ecological impacts in invaded regions. In Italy, monitoring and management programs largely rely on pheromone-based traps and attract-and-kill devices, while the effectiveness of feeding kairomones alone and the role of lure formulation parameters remain insufficiently evaluated. We assessed the field performance of synthetic kairomone blends based on 2-Phenylethyl propionate and eugenol, testing the effects of blend concentration, ethanol content and the addition of geraniol. Field experiments were conducted at four sites in Northern Italy. Captures and sex ratio were analysed using generalised linear mixed-effects models. Feeding-kairomone lures captured significantly more beetles than apple cider vinegar and water controls. Within kairomone treatments, higher blend concentrations increased captures, while ethanol content also significantly influenced trap efficiency, with the 10% ethanol dilution outperforming the 30% dilution. In contrast, the addition of geraniol did not affect trap efficiency. Lure formulation did not introduce any detectable sex bias, as the sex ratio of captured beetles was not influenced by lure concentration or composition. These results demonstrate that feeding kairomones alone provide a robust attraction cue for P. japonica and that lure formulation is a key determinant of trap performance, supporting their use in pheromone-independent monitoring and management strategies.