GREEN LEAF VOLATILES AS ANTIAGGREGANTS FOR THE MOUNTAIN PINE-BEETLE, DENDROCTONUS-PONDEROSAE HOPKINS (COLEOPTERA, SCOLYTIDAE)

We tested the hypothesis that green leaf volatiles act as antiaggregan ts for the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins . In coupled gas chromatographic-electroantennographic detection (GC-E AD) analysis MPB antennae responded to 30 ng doses of all six-carbon g reen leaf alcohols tested [1-hexanol, (E)-2-hexen-1-ol, (Z)-2-hexen-1- ol, (E)-3-hexen-1-ol, and (Z)-3-hexen-1-ol], but not to the aldehydes, hexanal or (E)-2-hexenal, or to alcohol or aldehyde homologues with m ore or fewer than six carbon atoms. In field trapping experiments a bl end of green leaf alcohols [1-hexanol, (Z)-2-hexen-1-ol, (E)-3-hexen-1 -ol and (Z)-3-hexen-1-ol] effectively disrupted the response to attrac tive semiochemicals; a blend of the aldehydes hexanal and (E)-2-hexena l was inactive. The two best disruptants, (E)-2-hexen-1-ol and (Z)-3-h exen-1-ol, reduced catches of both sexes to levels not significantly d ifferent from catches in unbaited control traps. They also reduced the attack on trees baited with attractive MBP pheromones to a level not significantly different from that on unbaited control trees. Neither o f the clerid predators captured, Enoclerus sphegeus (F.) nor Thanasimu s undatulus (Say), was repelled by green leaf volatiles. Our results s uggest that green leaf alcohols are promising disruptants which may be used to supplement the antiaggregation pheromone, verbenone, in prote cting single high-value trees as well as carefully selected stands wit h low-level populations of MPBs.