Abstract Hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), has devastated eastern hemlock (Tsuga canadensis [L.] Carriere) in a major portion of its native range in eastern North America. Population dynamics of HWA in the absence of predators have been studied for decades. After many years and much effort directed towards rearing and releasing biological control agents to manage HWA, one of these agents, Laricobius nigrinus Fender (Coleoptera: Derodontidae), is now successfully established at significant densities at sites from the southern to the mid-Atlantic states of the eastern U.S. However, high densities of HWA still persist at many locations throughout the region and spread of HWA and associated damage to hemlock continues. Population models for HWA have suggested that even upwards of 90% predation on eggs laid by the overwintering sistens generation will have minimal effect in reducing the population densities of HWA, if HWA are at high density. In this study, we tested the ability of L. nigrinus to reduce HWA densities, and experimentally tested these model predictions to better understand what impact, if any, L. nigrinus has on HWA densities. By using predator exclusion cages at field sites with well-established populations of L. nigrinus, we were able to record HWA densities, fecundity, overwintering mortality, and predation by L. nigrinus, as well as the proportion of branch tips producing new growth on study trees. Using our field-collected data, we refitted the model in ways that allowed us to predict what population densities we could expect for the following summertime progrediens generation given previous HWA density and levels of L. nigrinus. In both years, we found that despite high rates (greater than 80% ovisac predation) of predation by L. nigrinus on uncaged branches compared to caged branches, there were no significant differences in subsequent densities of the HWA spring generation between caged and uncaged treatments, as predicted by our model. In 2018, our field-collected densities of the summer progrediens generation were lower than what was predicted by the model in both predator exclusion treatments, possibly due to the model not incorporating tree health and climatic factors. Simulation models of pest insect populations based on field-collected data such as fecundity, density, overwintering mortality, and predation, could prove to be important in informing researchers and managers about the role of the biological control agent in the population dynamics of the target host.

中文翻译：

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在美国东部引入的捕食者 Laricobius nigrinus 捕食越冬一代卵囊后，Adelges tsugae 春季一代的反弹

摘要 铁杉羊毛 adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), 已经摧毁了北美东部大部分原产地的东部铁杉 (Tsuga canadensis [L.] Carriere)。在没有捕食者的情况下，HWA 的种群动态已经研究了几十年。经过多年致力于培育和释放生物控制剂以管理 HWA，其中一种生物控制剂 Laricobius nigrinus Fender（鞘翅目：Derodontidae）现已成功地在从南部到大西洋中部各州的地点以显着密度成功建立美国东部地区 然而，该地区的许多地方仍然存在高密度的 HWA，并且 HWA 的传播和对铁杉的相关损害仍在继续。HWA 的种群模型表明，如果 HWA 处于高密度，即使 90% 以上对越冬 sistens 一代产卵的捕食对降低 HWA 种群密度的影响也很小。在这项研究中，我们测试了 L. nigrinus 降低 HWA 密度的能力，并通过实验测试了这些模型预测，以更好地了解 L. nigrinus 对 HWA 密度的影响（如果有的话）。通过在具有完善的 L. nigrinus 种群的野外场地使用捕食者排除笼，我们能够记录 HWA 密度、繁殖力、越冬死亡率和 L. nigrinus 的捕食，以及产生新生长的分支尖端的比例研究树木。使用我们现场收集的数据，我们以某种方式重新拟合了模型，使我们能够根据之前的 HWA 密度和 L. nigrinus 的水平预测接下来的夏季 progrediens 世代的种群密度。在这两年中，我们发现尽管与笼养的树枝相比，L. nigrinus 在未笼养的树枝上的捕食率很高（超过 80% 卵囊捕食），但在笼养和未笼养的处理之间，HWA 春季代的后续密度没有显着差异，正如我们的模型所预测的那样。2018 年，我们在野外采集的夏季 progrediens 代密度低于模型在两种捕食者排除处理中的预测值，这可能是由于模型没有考虑树木健康和气候因素。基于田间采集数据的害虫种群模拟模型，如繁殖力、