Acetic acid enhances attraction to and colonization of wood bolts by ambrosia beetles (Coleoptera: Curculionidae: Scolytinae).

Certain invasive ambrosia beetles are attracted to and colonize physiologically stressed trees emitting ethanol. Xylosandrus germanus (Blandford) and Xylosandrus crassiusculus (Motschulsky) are attracted to trees emitting ethanol and are 2 of the most damaging invasive ambrosia beetles in North America. Acetic acid has been detected in stressed trees emitting ethanol, but whether it has a role in ambrosia beetle ecology is unknown. Sections of tree stems (bolts) were soaked in various dilutions of acetic acid alone and mixed with a 5% dilution of ethanol, then deployed in a field near a woodland. Bolts soaked in 5% or 10% dilutions of acetic acid were more attractive to X. germanus and X. crassiusculus than bolts soaked in dilutions of 0.1% or 1.0%. Dilutions of acetic acid mixed with 5% ethanol were more attractive to X. germanus and X. crassiusculus than similar dilutions of acetic acid alone or 5% ethanol alone. Furthermore, more offspring were produced in bolts soaked in mixtures of acetic acid and 5% ethanol than either compound alone. This information helps improve our knowledge of the physiological conditions in trees that make them suitable for colonization by X. germanus and X. crassiusculus. Furthermore, the increased attraction of damaging ambrosia beetles to acetic acid + ethanol could be useful for improving baits used for monitoring emergence of X. germanus and X. crassiusculus in spring.