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Conophtorin enhances the electroantennogram and field behavioral response of Xylosandrus germanus (Coleoptera: Curculionidae) to ethanol

RANGER, Christopher M., GORZLANCYK, Austin M., ADDESSO, Karla M., OLIVER, Jason B., REDING, Michael E., SCHULTZ, Peter B., Held, David W.
Agricultural and forest entomology 2014 v.16 no.4 pp. 327-334
Curculionidae, Xyleborinus, Xyleborus, Xylosandrus crassiusculus, bait traps, electroantennography, ethanol, insect attractants, insect behavior, semiochemicals, smell, synergism, terpinolene, trapping, verbenone
Ethanol acts as a long range cue that aids Xylosandrus germanus (Blandford) in locating living, but weakened trees. Conophthorin is associated with a variety of deciduous trees and enhances X. germanus’ attraction to vulnerable trees. Electroantennogram (EAG) and field trapping experiments were conducted with conophthorin and other selected semiochemicals to assess their influence on X. germanus’ response to ethanol and determine if EAG responses provided an indication of field behavioral activity. Semiochemicals were chosen based on their likelihood of enhancing (i.e. conophthorin), reducing (i.e. verbenone), or having a negligible effect (i.e. lineatin, retusol, sulcatol, and terpinolene). Ethanol plus conophthorin elicited a larger EAG response amplitude than ethanol plus any of the remaining semiochemicals at stimulus concentrations of 0.2, 2, and 200 µg. EAG responses to ethanol plus the remaining semiochemicals were indistinguishable. Ethanol plus conophthorin attracted more X. germanus, Euwallacea validus (Eichhoff), and Xyleborus pelliculosus Eichhoff than traps baited with ethanol alone, and a synergistic effect was detected for X. germanus and E. validus. In contrast, retusol, sulcatol, terpinolene, and verbenone reduced the attractiveness of ethanol to X. germanus, E. validus, Monarthrum fasciatum (Say), Xyleborinus saxesenii (Ratzeburg), Xylosandrus crassiusculus (Motschulsky), X. pelliculosus, and/or Anisandrus sayi Hopkins. While ethanol acts as an important olfactory cue for X. germanus, other volatiles can enhance (i.e. conophthorin) or reduce (i.e. retusol, terpinolene, and verbenone) orientation to ethanol. The larger EAG response generally elicited by conophthorin, and corresponding enhanced field activity, also suggests EAG analyses may be useful for identifying potential attractants.