USDA Forest Service, Southern Research Station, 2500 Shreveport Highway, Pineville LA 71360, USA.
Department of Statistics, North Carolina State University, Raleigh, NC 27695, USA.
Environ Entomol. 2021 Dec 17;50(6):1304-1310. doi: 10.1093/ee/nvab092.
Semiochemical background in the environment can influence insect orientation to release points of the same or different semiochemicals. endo-Brevicomin is a pheromone component of the tree-killing bark beetle Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) that has a biphasic dose-response curve, enhancing attraction at low release rates but reducing attraction at high rates. We investigated the effect of artificial manipulation of background levels of endo-brevicomin on D. frontalis responses to sources of aggregation attractant in the field. Traps baited with the aggregation pheromone component frontalin and the host odor alpha-pinene were deployed either with or without a background of endo-brevicomin produced by three surrounding dispensers of this semiochemical each located 20 m away. Two tested levels of endo-brevicomin background caused catches to increase by an order of magnitude above those in the absence of background. Presence of background also altered the beetles' biphasic dose-response when endo-brevicomin dispensers were added to traps. Background reduced or concealed attraction-enhancement otherwise observed for low-release dispensers added to traps, and it decreased the release rate necessary to produce reductions in catches. We propose that spatial variability in abundance of natural, background sources of endo-brevicomin in the environment (i.e., infested trees) is a cause of the observed variability in effects of endo-brevicomin dispensers on southern pine beetle behavior in the field. Furthermore, our results illustrate the potential complexity of the density-dependent effects of biphasic pheromone components on bark beetle mass attack and colonization behavior.
环境中的半化学物质背景会影响昆虫对相同或不同半化学物质释放点的定向。endo-Brevicomin 是一种树杀虫树皮甲虫（Dendroctonus frontalis Zimmermann）（鞘翅目：Curculionidae：Scolytinae）的信息素成分，具有双相剂量反应曲线，在低释放率下增强吸引力，但在高释放率下降低吸引力。我们研究了人为操纵 endo-Brevicomin 背景水平对 D. frontalis 在野外对聚集引诱剂源反应的影响。用聚集信息素成分 frontalin 和宿主气味 alpha-蒎烯诱饵的诱捕器，要么在没有 endo-Brevicomin 背景的情况下，要么在三个 20 米远的这种半化学物质周围分配器产生的 endo-Brevicomin 背景下进行部署。两种测试的 endo-Brevicomin 背景水平导致捕获量比没有背景时增加了一个数量级。存在背景也改变了当 endo-Brevicomin 分配器添加到诱捕器中时，甲虫的双相剂量反应。背景降低或掩盖了否则观察到的低释放分配器添加到诱捕器时的吸引力增强，并且降低了产生捕获量减少所需的释放率。我们提出，环境中天然背景来源 endo-Brevicomin 的丰度（即受感染的树木）的空间变异性是观察到 endo-Brevicomin 分配器对南方松树甲虫行为的野外效应变异性的原因。此外，我们的结果说明了双相信息素成分对树皮甲虫大规模攻击和定殖行为的密度依赖性效应的潜在复杂性。
