Abstract The ability of a biocontrol agent to acclimate to and survive the climate of intended introduction locations is a critical attribute for successful biological control of an invasive pest. We evaluated the cold tolerance of Spathius galinae Belokobylskij & Strazanac, a braconid parasitoid native to the Russian Far East introduced to the United States for biocontrol of the ash (Fraxinus spp.) pest, emerald ash borer (EAB), Agrilus planipennis Fairmaire, by measuring the supercooling point (SCP) of mature S. galinae larvae exposed to winter temperatures at four different field locations that span a gradient of plant hardiness zones. We observed a significant effect of overwintering location on SCPs of S. galinae larvae collected from field populations, with lower SCPs observed at locations with lower average minimum ambient temperatures. We also tested the SCP of three stages (early-instar, late-instar, and mature cocooned larvae) of lab-reared parasitoids and found that SCP did not significantly differ between stages of lab-reared S. galinae. Our findings provide strong evidence that S. galinae can reduce SCP in response to below-freezing temperatures. The increase in cold hardiness of S. galinae in response to below-freezing temperatures should be considered in delineation of the optimal geographic range for biocontrol releases against EAB in North America.

中文翻译：

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Spathius galinae（膜翅目：茧蜂科）的耐寒性，这是一种在北美引入用于生物防治翡翠灰蛀虫的幼虫寄生蜂

摘要 生物防治剂适应预期引入地点气候并在其中存活的能力是成功生物防治入侵害虫的关键属性。我们评估了 Spathius galinae Belokobylskij & Strazanac 的耐寒性，这是一种原产于俄罗斯远东的braconid 寄生蜂，被引入美国用于对灰 (Fraxinus spp.) 害虫、翡翠灰螟 (EAB)、Agrilus planipennis Fairmaire 进行生物防治。在跨越植物抗寒区梯度的四个不同现场位置测量暴露于冬季温度的成熟 S. galinae 幼虫的过冷点 (SCP)。我们观察到越冬地点对从野外种群中收集的 S. galinae 幼虫的 SCP 有显着影响，在平均最低环境温度较低的位置观察到的 SCP 较低。我们还测试了实验室饲养的寄生蜂三个阶段（早龄、晚龄和成熟茧幼虫）的 SCP，发现实验室饲养的 S. galinae 阶段之间的 SCP 没有显着差异。我们的发现提供了强有力的证据，证明 S. galinae 可以减少 SCP 以响应低于冰点的温度。在划定北美针对 EAB 的生物防治释放的最佳地理范围时，应考虑 S. galinae 响应于低于冰点的温度而增加的耐寒性。