Aggregation pheromone of a newly described spruce bark beetle, Ips shangrila Cognato and Sun, from China

Volatiles from male hindgut extracts of a newly described spruce bark beetle, Ips shangrila Cognato and Sun, from different attack phases were analyzed by GC-MS/FID with both polar and enantioselective columns. The GC-MS/FID analyses showed that unmated males (Phase 1) or males mated with 3 females (Phases 2-4) produced 2-methyl-3-buten-2-ol and 99%-(+)-ipsdienol as major components, and (-)-cis-verbenol, (-)-trans-verbenol, myrtenol and 2-phenyl ethanol as minor or trace components. The release of these male-produced compounds was confirmed by the analysis on aeration sample of an I. shangrila infested wind-thrown spruce trunk. The quantities of 2-methyl-3-buten-2-ol, cis-verbenol and trans-verbenol from male hindgut extracts were almost unchanged or even slightly increased during gallery development, while ipsdienol decreased dramatically after mating with three females. No obvious Ips-related aggregation pheromone components were detected in the female hindgut extract. A field trapping bioassay in Qinghai, China, showed that the ternary blends containing 2-methyl-3-buten-2-ol, (-)-cis-verbenol and 97%-(+)-ipsdienol or ([plus or minus])-ipsdienol, caught significantly more I. shangrila ([male] : [female] = 1:2.14) than did the unbaited control. Replacing 97%-(+)-ipsdienol (close to the naturally produced enantiomeric ratio) with ([plus or minus])-ipsdienol in the ternary blend seemed to reduce trap catches by 50%, but the difference was not statistically significant. Surprisingly, addition of (-)-trans-verbenol (at 0.2 mg/day) to the active ternary blends significantly reduced traps catches to the level not different from the unbaited control. Our results suggest that the two major components, 2-methyl-3-buten-2-ol and 99%-(+)-ipsdienol, plus a minor component, (-)-cis-verbenol, produced by fed males, are likely the aggregation pheromone components of I. shangrila.