PRIMARY ATTRACTION OF THE FIR ENGRAVER, SCOLYTUSVENTRALIS LECONTE (COLEOPTERA: SCOLYTIDAE).
J. E. Macías-Sámano, J. H. Borden, R. Gries, H. D. Pierce1,Jr., G. Gries, and G.G.S. King1
Centre for Pest Management, Department of Biological Sciences.
1Department of Chemistry, Simon Fraser University, Burnaby,British Columbia V5A 1S6, Canada.
In laboratory bioassays, Porapak Q-captured and steam-distilled volatilesfrom the bark of host trees, Abies grandis (Dougl.) Lindl.,particularly from root-rot infected trees, attracted 50-70 % of male andfemale fir engravers, Scolytus ventralis LeConte. GC-EAD analysesof Porapak Q-captured bark volatiles revealed 19 EAD-active compounds ofwhich 13 were identified by GC-mass spectrometry. In separate field experimentsmultiple-funnel traps baited with two blends of these 13 (synthetic) volatiles(one blend with limonene as a contaminant with B-phellandrene,and the other without) released at 28 and 34 mg per 24 hr, respectively,attracted 66 and 93 % of the total S. ventralis captured. The clerid,Thanasimus undulatus Say, also responded strongly to the kairomonalvolatiles. Additional experiments failed to disclose evidence for aggregationpheromones in S. ventralis. These included: laboratory bioassaysand differential GC-analysis of Porapak Q-captured volatiles from male-and female-infested logs, or trees undergoing mass attack in the field;GC analyses and/or bioassays of extracts from female accessory glands,extracted volatiles from emerged, attacking and juvenile hormone-treatedbeetles of both sexes; and videotape analysis of the behavior of attackingbeetles on the bark surface. We argue against the hypothesis of pheromone-mediatedsecondary attraction in S. ventralis, and conclude that the attackdynamics of this species can be explained solely by its sensitive primaryattraction response to host volatiles.