USDA Forest Service, Southern Research Station, 2500 Shreveport Hwy, Pineville, LA, 71360, USA.
J Chem Ecol. 2009 Oct;35(10):1222-33. doi: 10.1007/s10886-009-9705-6. Epub 2009 Nov 10.
Flight responses of the southern pine beetle, Dendroctonus frontalis Zimmermann, to widely-spaced (>130 m) traps baited with pine volatiles (in turpentine) and the female-produced pheromone component frontalin were enhanced when a bait containing the male pheromone component (+)-endo-brevicomin was attached directly to the trap. However, displacing this bait 4-16 m horizontally from the trap significantly increased its synergistic effect. (+)-endo-Brevicomin enhanced catch to the same degree when the bait was positioned either on the trap or 32 m away. In another experiment, pairs of frontalin/turpentine-baited traps were established with 4 m spacing between traps and >100 m spacing between pairs. Attachment of either a racemic or (+)-endo-brevicomin bait to one trap of a pair caused a significant increase in catch by both traps, but catch in the trap lacking endo-brevicomin was increased more than in its endo-brevicomin-baited twin. In a third experiment, widely-spaced groups of three traps (in a line with 1 and 4 m spacing between the middle and outer traps) were baited uniformly with frontalin and turpentine, and the release rate of (+)-endo-brevicomin from the middle trap was varied across three orders of magnitude. Release rates sufficient to enhance total D. frontalis catch by the trio also caused relatively higher catches to occur in the outer traps than in the middle one. These experiments indicated that both male and female D. frontalis fly to and land preferentially at sources of frontalin and host odors when these are located some distance away from a source of endo-brevicomin. This behavior may have evolved in D. frontalis to allow host-seeking beetles to locate growing, multi-tree infestations while avoiding fully-colonized trees within these infestations. Our data demonstrate that trap spacing alone can qualitatively change the outcome of bait evaluation trials and may explain why many earlier experiments with endo-brevicomin failed to identify it as an aggregation pheromone synergist for D. frontalis. We believe that important aggregative functions of semiochemicals of other bark beetle species may have been similarly overlooked due to choice of experimental procedures.
南方松大小蠹对相距较远（>130m）的诱捕器中的松挥发物（松节油）和雌性产生的信息素成分法尼醇的飞行反应增强了，当一个含有雄性信息素成分（+）-内型-芹子烯醇的诱饵直接附着在诱捕器上时。然而，将这种诱饵水平移动 4-16m 会显著增加其协同作用。当诱饵位于诱捕器上或 32m 远时，（+）-内型-芹子烯醇以相同的程度增强了捕获量。在另一个实验中，使用 4m 的间隔建立了一对法尼醇/松节油诱饵诱捕器，并且在诱捕器之间有>100m 的间隔。将一对诱捕器中的一个连接上一个外消旋或（+）-内型-芹子烯醇诱饵会导致两个诱捕器的捕获量显著增加，但是缺乏内型-芹子烯醇的诱捕器的捕获量增加得比其有内型-芹子烯醇诱饵的双胞胎诱捕器多。在第三个实验中，三个诱捕器（在中间和外部诱捕器之间以 1 和 4m 的间隔成一直线）被均匀地用法尼醇和松节油诱捕，并改变中间诱捕器中（+）-内型-芹子烯醇的释放率，跨越三个数量级。释放率足以增强整个 D. frontalis 捕获率的组合也导致外部诱捕器的捕获率相对高于中间诱捕器。这些实验表明，当法尼醇和寄主气味源距离内型-芹子烯醇源一定距离时，雌雄南方松大小蠹都会飞向并降落在这些源上。这种行为可能是在 D. frontalis 中进化而来的，使寻找寄主的甲虫能够定位生长中的多树侵染，同时避免侵染中的完全殖民化的树木。我们的数据表明，诱捕器的间隔可以定性地改变诱饵评估试验的结果，并且可能解释为什么许多早期的关于内型-芹子烯醇的实验未能将其鉴定为 D. frontalis 的聚集信息素协同剂。我们认为，由于实验程序的选择，其他树皮甲虫物种的半化学物质的重要聚集功能可能也被忽略了。
