ARS | Publication request: Ambrosia beetle (Coleoptera: Curculionidae) responses to volatile emissions associated with ethanol-injected Magnolia virginiana L.

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2012
Publication Date: June 15, 2012
Citation: Ranger, C.M., Reding, M.E., Schultz, P., Oliver, J. 2012. Ambrosia beetle (Coleoptera: Curculionidae) responses to volatile emissions associated with ethanol-injected Magnolia virginiana L. Environmental Entomology. 41(3):636-647.

Interpretive Summary: Ambrosia beetles pose a significant challenge to producers of ornamental nursery stock. Ethanol is the most attractive volatile compound known for Xylosandrus germanus and is used in traps to aid with monitoring flight activity and time insecticide applications. A series of laboratory and field-based experiments were conducted to assist with developing improved monitoring and management tactics. Injections of ethanol into Magnolia virginiana L. induced more ambrosia beetle attacks under field conditions than irrigating or baiting with ethanol, and no attacks occurred on water-injected trees. Traps baited with stems from ethanol-injected trees caught five times more X. germanus than ethanol-baited traps, and a positive correlation was observed between concentration of injected ethanol and cumulative ambrosia beetle attacks. Volatile emissions were characterized from the bark of ethanol- and water-injected M. virginiana up to 16 days after injection. Ethanol was the most predominant compound emitted from ethanol-injected trees, but steadily declined over the course of 16 days. A variety of monoterpenes were also emitted in trace amounts from ethanol-injected trees. Ethanol was not emitted from water-injected M. virginiana. Antennal responses of X. germanus to volatiles from ethanol-injected M. virginiana occurred for ethanol, but not the various monoterpenes. Xylosandrus germanus and other ambrosia beetles were also equally attracted to traps baited with ethanol alone compared to a synthetic mixture of ethanol plus various monoterpenes formulated to mimic ethanol-injected M. virginiana. Collectively, these results demonstrate the significance of ethanol as a primary volatile cue used by X. germanus to locate suitable hosts. In particular, the role of ethanol emission in attracting and selectively inducing ambrosia beetle attacks was characterized. Injecting concentrated solutions of ethanol may be useful for establishing odor-based trap trees, which could aid with monitoring programs and/or potentially deflect ambrosia beetles away from valuable nursery stock.

Technical Abstract: Ethanol represents a primary attractant for Xylosandrus germanus (Blandford) and several other species of ambrosia beetles known to colonize ornamental nursery stock. Stem injections of ethanol into Magnolia virginiana L. induced more ambrosia beetle attacks under field conditions than irrigating or baiting with ethanol, and no attacks occurred on water-injected trees. Traps baited with bolts from ethanol-injected M. virginiana caught five times more X. germanus than ethanol-baited traps. A positive correlation was also observed between concentration of injected ethanol and cumulative ambrosia beetle attacks. Solid phase microextraction-gas chromatography-mass spectrometry characterized emissions from stems of ethanol- and water-injected M. virginiana at 1, 2, 10, and 16 d after treatment (DAT). Ethanol was the most predominant compound emitted from ethanol-injected trees at each time point, but steadily declined over the course of 16 DAT. A variety of monoterpenes were also emitted in trace amounts from ethanol-injected trees. Ethanol was not emitted from water-injected M. virginiana. Antennal responses of X. germanus via gas chromatography-electroantennographic detection to volatiles from ethanol-injected M. virginiana occurred for ethanol, but not the various monoterpenes. Xylosandrus germanus and other ambrosia beetles were equally attracted to traps baited with ethanol alone compared to a synthetic mixture of ethanol plus various monoterpenes formulated to mimic ethanol-injected M. virginiana. Injecting concentrated solutions of ethanol may be useful for establishing odor-based trap trees, which could aid with monitoring programs and/or potentially deflect ambrosia beetles away from valuable nursery stock.