Sullivan Brian T, Brownie Cavell
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. 2022 Apr 22;51(2):340-350. doi: 10.1093/ee/nvac006.
Aggressive bark beetles colonize and kill healthy conifers through pheromone-mediated mass aggregation. In several species, the focal point of aggregation moves progressively from mass-attacked 'focus trees' to adjacent, unattacked 'recipient trees', resulting in infestation growth. This process, termed 'switching', is hypothesized to be mediated in whole or in part by antiaggregation pheromones released by beetles as colonization intensifies on a focus tree. We tested this hypothesis with the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), by using a windvane apparatus that maintained an unbaited, black, cylindrical trap (surrogate for a recipient tree) continuously 4 m downwind from an identical trap baited with synthetic aggregation attractant (surrogate for a focus tree). In two of three replicated trials, addition of pheromone components with antiaggregation activity, endo-brevicomin or verbenone, to the upwind trap caused a significant but small (<15%) increase in the proportion of beetles caught in the downwind trap. In one of two trials with endo-brevicomin, this shift was associated with a significant reduction in catches in the downwind trap and an overall reduction in catches of beetles by the trap pair. This suggests that an inhibitor-induced increase in landings on the recipient relative to the focus tree may be countered by the radial effects of the inhibitor, which at sufficiently high release may reduce responses to both the focus and recipient tree. We discuss spatial factors that might govern the role of antiaggregation pheromones in stimulating infestation growth as well as additional factors that likely govern switching behavior.
具有攻击性的树皮甲虫通过信息素介导的群体聚集来侵害并杀死健康的针叶树。在几个物种中，聚集的焦点会逐渐从遭受大量攻击的“焦点树”转移到相邻的未受攻击的“接收树”，从而导致虫害蔓延。这个过程被称为“转换”，据推测，它全部或部分地由随着甲虫在焦点树上的定殖加剧而释放的反聚集信息素介导。我们以南方松甲虫（Dendroctonus frontalis Zimmermann，鞘翅目：象甲科：小蠹亚科）为对象，通过使用风向标装置来验证这一假设。该装置将一个未设诱饵的黑色圆柱形诱捕器（作为接收树的替代物）持续保持在距离一个用合成聚集引诱剂设饵的相同诱捕器（作为焦点树的替代物）顺风4米处。在三个重复试验中的两个试验中，向上风处的诱捕器添加具有反聚集活性的信息素成分内 - 短叶松醇或马鞭草烯酮，导致在顺风处诱捕器中捕获的甲虫比例显著但小幅（<15%）增加。在使用内 - 短叶松醇的两个试验中的一个试验中，这种转移与顺风处诱捕器捕获量的显著减少以及诱捕器对捕获的甲虫总量的减少有关。这表明，抑制剂诱导的相对于焦点树在接收树上着陆的增加可能会被抑制剂的径向效应抵消，在释放量足够高时，抑制剂可能会降低对焦点树和接收树的反应。我们讨论了可能控制反聚集信息素在刺激虫害蔓延中作用的空间因素，以及可能控制转换行为的其他因素。
