Variation in manuka oil lure efficacy for capturing Xyleborus glabratus (Coleoptera: Curculionidae: Scholytinae), and Cubeb oil as an alternative attractant
Redbay ambrosia beetle, Xyleborus glabratus Eichoff, is an exotic species to North America vectoring a deadly vascular wilt disease of redbay [Persea borbonia (L.) Spreng], swampbay [P. palustris (Raf.) Sarg.], avocado (P. americana Mill.), and sassafras [Sassafras albidum (Nutt.) Nees]. Xyleborus glabratus is attracted to manuka oil lures, which are commercially available, and phoebe oil. Variable efficacy of manuka oil lures and insufficient availability of phoebe oil prompted us to investigate the reasons behind changes in manuka oil lure efficacy and to test cubeb oil, a readily available essential oil from Piper cubeba L. seeds, as an alternative attractant. Attraction, release rates and durations, and volatile composition of manuka oil lures manufactured in 2008 were compared with manuka oil lures manufactured in 2012, and to whole and a distilled fraction of cubeb oil. Manuka oil lures from 2008 were more attractive to X. glabratus than controls for 8 wk, whereas lures from 2012 were attractive for only 2 wk. Cubeb oil and the distilled fraction of it were as attractive as or more attractive than manuka oil in three trials. In gravimetric studies, manuka oil lures from 2008 and cubeb oil lures continued to release volatiles for 57 d, whereas lures from 2012 stopped after 16 d. The chemical composition of volatiles released from new manuka oil lures from 2008 was similar to 2012; however, a preservative (butylated hydroxytoluene) was detected in the 2008 lures. Cubeb oil was an effective attractant for X. glabratus that lasted 8-9 wk when released from bubble lures.