Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are among the most devastating pests of orchards, nurseries, and forests. Improving trap design and ethanol lures for capturing ambrosia beetles is necessary to develop effective monitoring and management strategies. In this 2-year study, we assessed 4 trap designs and 3 commercially formulated ethanol lures to refine trapping methods tailored for orchard environments in the eastern United States. Our investigation included orchards in 2 regions, Georgia (pecan orchards) and New York (apple orchards), targeting major ambrosia beetle (Coleoptera: Curculionidae) pest species such as Xylosandrus crassiusculus (Motschulsky), X. compactus (Eichhoff), X. germanus (Blandford), and Anisandrus maiche (Stark). Among the trap designs evaluated, clear sticky cards were most effective for capturing ambrosia beetles across orchard locations. Notably, in Georgia, sticky cards paired with specific low-release ethanol lures demonstrated enhanced capture of X. crassiusculus and X. compactus, 2 key ambrosia beetle pests found infesting young pecan trees. Similarly, in New York, sticky cards baited with low-release ethanol lures captured the highest rates of X. germanus and A. maiche, thus indicating its suitability for diverse ambrosia beetle populations. Overall, our study provides practical implications for tailoring trapping protocols to optimize ambrosia beetle management strategies in orchard settings.

Anisandrus maiche Stark (Coleoptera: Curculionidae: Scolytinae) is a non-native ambrosia beetle from central Asia that has been spreading throughout the eastern United States since 2005. Preferred hosts of A. maiche are not well characterized within its currently invaded range, but it is established in managed and natural forests throughout Indiana. Current monitoring and detection efforts for this beetle rely on ethanol-baited traps, but fungal volatiles may alter the attraction of A. maiche to ethanol. In this study, we conducted trapping experiments in Indiana to determine the extent to which a suite of common fungal alcohols influences the response of A. maiche to ethanol-baited traps. We then evaluated isoamyl and isobutyl alcohol as potential attractants for A. maiche and their ability to enhance attraction to ethanol. Lastly, we used SPME-GC-MS to identify volatiles from Ambrosiella cleistominuta (Mayers & Harr.), the fungal symbiont of A. maiche, grown for 7 and 14 days on malt extract agar. Benzyl alcohol, isobutyl alcohol, hexanol, methyl phenylacetate, phenethyl alcohol, and piperitone reduced the attraction of A. maiche to ethanol-baited traps in the field. Moreover, adding methyl benzoate and isoamyl alcohol individually to ethanol-baited traps did not further increase A. maiche capture. When paired with ethanol, isoamyl alcohol repelled beetles in the early flight period but did not significantly increase trap capture during the fall flight. These results represent a first step in understanding the role of fungal volatiles in the colonization behavior of A. maiche and may ultimately inform management strategies for this species.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are among the most devastating pests of orchards, nurseries, and forest ecosystems. Anisandrus maiche (Kurentzov) has been regularly captured in ethanol-baited traps along woody edges of apple (Malus domestica (Suckow) Borkh.) orchards in western New York alongside a known apple pest, Xylosandrus germanus (Blandford). However, this species has yet to be a confirmed pest of apple trees. In winter 2024, we conducted a series of dissections of potted apple trees with visible ambrosia beetle attacks (i.e. entry holes, exit holes). Our examination revealed the presence of active A. maiche galleries housing mainly larvae, a few adults, and the fungal symbiont Ambrosiella cleistominuta C. Mayers & T.C. Harr This is a first report of Anisandrus maiche attacking apple trees.

Rapid ‘ōhiʻa death (ROD), caused by fungal pathogens Ceratocystis lukuohia and Ceratocystis huliohia, is devastating ʻōhiʻa (Metrosideros polymorpha), the keystone forest tree species of Hawaiʻi. Ceratocystidaceae fungi produce fruity volatile organic compounds (VOCs) and sticky sexual spores, suggesting they are adapted for insect dispersal. In this study, we explored chemical signaling of the causal agents of the ROD disease complex and how those VOCs mediate ambrosia beetle (Coleoptera: Curculiondiae: Scolytidae)-plant interactions. Four species of ambrosia beetles (Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, and Xyleborus perforans) are direct vectors of the ROD pathogens in addition to spreading the fungi indirectly through contaminated frass. To further understand the extent to which semiochemicals mediate relationships between agents of the ROD pathosystem, we identified fungal VOCs both in vitro and in vivo. We then tested behavioral responses of the ROD-associated ambrosia beetles to the odor of the fungi using still-air olfactometer assays. Similar fruity and banana-like fusel alcohols and acetates were produced by C. lukuohia and C. huliohia in culture and when colonizing ‘ōhiʻa seedlings, which could be detected one-day post-inoculation, nine days before symptom onset. X. affinis was attracted to both C. lukuohia and C. huliohia, while X. ferrugineus positively responded to C. lukuohia and X. perforans to C. huliohia. These findings suggest a semiochemical association and potential support for the hypothesis of coevolutionary history between Ceratocystis fungi and insects.