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

Abstract

Abstract Lure attraction strength for red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) observed previously in US Pacific Northwest ponderosa pine forests is (−)‐β‐pinene+ethanol > (+)‐3‐carene+ethanol, but untested elsewhere in its western US range. Thus, both were tested with (−)‐β‐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, (−)‐β‐pinene+ethanol > (−)‐β‐pinene > 3‐carene = 3‐carene+ethanol > ethanol > blank, whereas in the cut‐unburned Arizona site it was 3‐carene+ethanol > 3‐carene = (−)‐β‐pinene+ethanol > (−)‐β‐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 (−)‐β‐pinene varied, from a stronger attractant than (+)‐3‐carene in Oregon and California, to a weaker lure than (+)‐3‐carene in Arizona. This (−)‐β‐pinene variability was minimized when released in combination with ethanol, making (−)‐β‐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.