Oystershell scale (OSS; Lepidosaphes ulmi) is an emerging invasive insect that poses a serious threat to conservation of quaking aspen (Populus tremuloides) in the southwestern US. Although OSS has been an urban pest in the US since the 1700s, it has recently spread into natural aspen stands in northern Arizona, where outbreaks are causing dieback and mortality. We quantified the ongoing outbreak of OSS at two scales: (1) local severity at two sites and (2) regional distribution across northern Arizona. Our regional survey indicated that OSS is widespread in lower elevation aspen stands and is particularly pervasive in ungulate exclosures. Advanced regeneration had the highest levels of infestation and mortality, which is concerning because this size class is an underrepresented component of aspen stands in northern Arizona. If OSS continues to spread and outbreaks result in dieback and mortality like we observed, then aspen in the southwestern US, and perhaps beyond, will be threatened. Three interacting factors contribute to OSS’s potential as a high-impact invasive insect that could spread rapidly: (1) its hypothesized role as a sleeper species, (2) potential interactions between OSS and climate change, and (3) the species’ polyphagous nature. Invasive pests like OSS pose an imminent threat to native tree species and, therefore, represent an immediate research and monitoring priority. We conclude with recommendations for future research and monitoring in order to understand OSS’s biology in natural aspen stands, quantify impacts, limit future spread, and mitigate mortality and loss of aspen and other host species.

牡蛎壳鳞片（OSS; Lepidosaphes ulmi）是一种新兴的侵入性昆虫，对地震白杨（Populus tremuloides）的保存构成严重威胁。）在美国西南部。自从1700年代以来，OSS在美国一直是一种城市病虫害，但它最近已扩散到亚利桑那州北部的天然白杨林中，那里的暴发导致死亡和死亡。我们以两个尺度量化了持续不断的OSS爆发：（1）两个地点的局部严重程度，以及（2）亚利桑那北部地区的区域分布。我们的区域调查表明，OSS在较低高度的白杨林中很普遍，在有蹄类动物的排泄物中尤其普遍。晚期再生的侵扰和死亡率最高，这令人担忧，因为这种规模的树种在亚利桑那州北部的白杨林中代表性不足。如果像我们观察到的那样，开放源码软件继续传播并且爆发导致死亡和死亡，那么美国西南部甚至其他地区的白杨树将受到威胁。三个相互作用的因素有助于OSS成为可能迅速传播的高影响力入侵昆虫的潜力：（1）假设它是一个睡眠物种，（2）OSS与气候变化之间的潜在相互作用，以及（3）该物种的多食性。像OSS这样的入侵性害虫对本土树种构成了迫在眉睫的威胁，因此代表着立即进行研究和监测的重点。最后，我们提出了有关未来研究和监测的建议，以便了解天然白杨林中OSS的生物学，量化影响，限制未来的传播并减轻白杨及其他寄主物种的死亡率和损失。（3）该物种的多食性。像OSS这样的入侵性害虫对本土树种构成了迫在眉睫的威胁，因此代表着立即进行研究和监测的重点。最后，我们提出了有关未来研究和监测的建议，以便了解天然白杨林中OSS的生物学，量化影响，限制未来的传播并减轻白杨及其他寄主物种的死亡率和损失。（3）该物种的多食性。像OSS这样的入侵性害虫对本土树种构成了迫在眉睫的威胁，因此代表着立即进行研究和监测的重点。最后，我们提出了有关未来研究和监测的建议，以便了解天然白杨林中OSS的生物学，量化影响，限制未来的传播并减轻白杨及其他寄主物种的死亡率和损失。