Byers, J.A., Lanne, B.S., & Lfqvist, J. 1989c. Host-tree unsuitability recognized by pine shoot beetles in flight. Experientia 45:489-492.

Abstract-- Tomicus piniperda on Scotch pine In spring, the landing rate of flying European pine shoot beetles, Tomicus piniperda L., on injured Scots pine diminishes as colonization continues. This is due to olfactory cues that indicate progressive host degradation. Verbenone was shown to play a role in the beetle's recognition of this unsuitability of a formerly suitable host, since the compound was increasingly released from colonized tree sections as they aged, but not from uninfested sections. Also, the release of verbenone at natural rates in the forest inhibited the attraction of beetles to host monoterpenes.
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Chemical Ecology