To develop a monitoring bait for O. erosus, we tested various semiochemicals. In experiment 1, racemic ipsidienol and 2-methyl-3-buten-2-ol (MB) were not attractive alone but highly attractive combined together. In experiment 2, a low (0.5 – 1.8 mg/d) to medium (17-60 mg/d) release rate of MB in the presence of racemic ipsdienol elicited the greatest response. In experiment 3, O. erosus responded similarly to low to high release rates (0.11- 5.6 mg/d) of racemic ipsdienol when combined to MB. In experiment 4, O. erosus was highly attracted to a bait with (-)-ipsdienol, while (+)-ipsdienol was interrupting flight response. Experiment 5 confirmed that both MB and (-)-ipsdienol were not attractive alone but attractive synergistically. Experiment 6 showed that the presence of á-pinene of any enantiomeric form appeared to enhance attraction when combined with MB and (-)-ipsdienol.