Angiosperm bark volatiles disrupt response of Douglas-fir beetle, Dendroctonus pseudotsugae, to attractant-baited traps

Antennally active, bark-derived, angiosperm volatiles were rested singly an d in groups for their ability to disrupt the response of the Douglas-fir be etle (DFB), Dendroctonus pseudotsugae, to attractant-baited multiple-funnel traps. One compound. conophthorin, was active alone in reducing the respon se of beetles to the baited traps. Further experiments showed disruptive ac tivity in two aliphatic green-leaf alcohols [1-hexanol and (Z)-3-hexen-1-ol ], as well as guaiacol and benzyl alcohol. and three aliphatic aldehydes [n onanal, hexanal, and (E)-2-hexenal] but not in two aromatic aldehydes (benz aldehyde and salicylaldehyde). Every binary combination that included conop hthorin or any two of the other groups, except aromatic aldehydes, signific antly reduced the response of beetles to baited traps. Various ternary mixt ures and the complete mixture of all the groups were generally the most eff ective treatments. These results provide evidence that DFBs recognize and a void nonhosts while flying rather than landing on candidate hosts and testi ng them while in contact with the tree. Nonhost angiosperm bark volatiles m ay have practical utility on their own or in combination with the antiaggre gation pheromone 3-methylcyclohex-3-en-1-one (MCH) to protect single trees, logs, or stands from attack by the DFB.