Differential flight responses of two ambrosia beetles to ethanol as indicators of invasion biology: The case with Kuroshio shot hole borer (Euwallacea kuroshio) and fruit tree pinhole borer (Xyleborinus saxesenii)

Authors: CHEN, YIGEN - University Of California, Davis; COLEMAN, TOM - Forest Service (FS); Ranger, Christopher; SEYBOLD, STEVEN - Forest Service (FS)

Submitted to: Ecological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2020
Publication Date: 1/19/2021
Citation: Chen, Y., Coleman, T.W., Ranger, C.M., Seybold, S.J. 2021. Differential flight responses of two ambrosia beetles to ethanol as indicators of invasion biology: The case with Kuroshio shot hole borer (Euwallacea kuroshio) and fruit tree pinhole borer (Xyleborinus saxesenii). Ecological Entomology. 46(3):651-667. https://doi.org/10.1111/een.13013.
DOI: https://doi.org/10.1111/een.13013

Interpretive Summary: Depending on the species, exotic ambrosia beetles attack trees ranging from healthy to weakened, dying, or dead trees. Compared to weakened trees, healthy trees emit little to no ethanol, which is stress-induced and a by-product of anaerobic respiration. The current study tested the attraction of two exotic ambrosia beetles, Kuroshio shot hole borer (KSHB), Euwallacea nr. fornicatus, and fruit-tree pinhole borer, Xyleborinus saxeseni, to four treatments with or without ethanol. GC-MS analyses confirmed the release of ethanol from ethanol lures and boxelder logs filled with ethanol. Kuroshio shot hole borer was not attracted to any ethanol treatment, whereas X. saxesenii responded positively to the ethanol treatments. The boxelder bolt infused with ethanol was the most attractive treatment to X. saxesenii. We propose that the differential behavioral responses of these two ambrosia beetles to ethanol corresponds to their differential aggressiveness for attacking healthy trees: KSHB attacks healthy trees, whereas X. saxeseni attacks weakened trees. The proposal is further substantiated by a literature survey on bark and ambrosia beetles from Scolytinae. The survey indicates that the majority of bark and ambrosia beetles respond positively to ethanol. Although ethanol is widely used and is an effective lure for attraction of many bark and ambrosia beetles, findings from this current study and many others necessitate research and development of alternative lures for more aggressive species which are ecologically and economically more devastating.

Technical Abstract: Host selection and utilization by ambrosia beetles ranges from healthy trees to weakened, dying, or dead trees. Compared to weakened trees, healthy trees emit little to no ethanol, which is stress-induced and a by-product of anaerobic respiration. The current study tested the attraction of two invasive ambrosia beetles, Kuroshio shot hole borer (KSHB), one member of the cryptic species, Euwallacea nr. fornicatus, and fruit-tree pinhole borer, Xyleborinus saxeseni, to four treatments with or without ethanol. GC-MS analyses confirmed the release of ethanol from the ethanol lure and boxelder log filled with ethanol and not from the other two treatments. Kuroshio shot hole borer was not preferentially attracted to any ethanol treatment, whereas X. saxesenii responded positively to the ethanol treatments. The boxelder bolt infused with ethanol was the most attractive treatment to X. saxesenii. We propose that the differential behavioral responses of these two ambrosia beetles to ethanol corresponds to their differential aggressiveness for attacking healthy trees: KSHB attacks healthy trees, whereas X. saxeseni attacks weakened trees. The proposal is further substantiated by a literature survey on bark and ambrosia beetles from Scolytinae. The survey also indicates that the majority of bark and ambrosia beetles from Scolytinae respond positively to ethanol. Although ethanol is widely used and is an effective lure for attraction of many bark and ambrosia beetles, findings from this current study and many others necessitate research and development of alternative lures for more aggressive species which are ecologically and economically more devastating.