Red turpentine beetle primary attraction to β-pinene or 3-carene (with and without ethanol) varies in western US pine forests

Lure attraction strength for red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) observed previously in US Pacific Northwest ponderosa pine forests is (-)-beta-pinene+ethanol > (+)-3-carene+ethanol, but untested elsewhere in its western US range. Thus, both were tested with (-)-beta-pinene, (+)-3-carene, ethanol, and a blank in Oregon and California sites burned by wildfire, whereas in Arizona the first four lures were tested in a thinned-unburned site. The D. valens responses in burned Oregon and California sites were similar, (-)-beta-pinene+ethanol > (-)-beta-pinene > 3-carene = 3-carene+ethanol > ethanol > blank, whereas in the cut-unburned Arizona site it was 3-carene+ethanol > 3-carene = (-)-beta-pinene+ethanol > (-)-beta-pinene. Whether this variation was influenced by beetle genetic differences, or chemical and physical parameters in the different environments and remaining stressed host resources 1-year post disturbance warrants additional study. Responses to (-)-beta-pinene varied, from a stronger attractant than (+)-3-carene in Oregon and California, to a weaker lure than (+)-3-carene in Arizona. This (-)-beta-pinene variability was minimized when released in combination with ethanol, making (-)-beta-pinene+ethanol the most consistent attractant of those tested across the three states, and a reliable lure for detection, monitoring, and management projects for D. valens in western US pine forests.