Department of Environmental Conservation, University of Massachusetts, Amherst, MA, USA.
Environ Entomol. 2022 Jun 17;51(3):545-556. doi: 10.1093/ee/nvac031.
Species of knotweeds, Reynoutria spp. Houtt. (Caryophyllales: Polygonaceae), including Japanese knotweed (R. japonica Houtt.), are among the most invasive and ecologically destructive plant species introduced to North America and Europe. The Kyushu strain of the psyllid Aphalara itadori Shinji (Hemiptera: Aphalaridae) has been approved as a biological control agent for release against Japanese knotweed in the United Kingdom, Canada, and the United States. However, recent reports from Canada suggest that both biotic and abiotic factors may limit its establishment. Therefore, we examined the potential role of predation by comparing open- versus closed-sleeve treatments, and climate mis-matches by collecting temperature data from release sites and performing climate suitability analyses using MaxEnt. Our results indicated that populations of the Kyushu strain could only be maintained in the field in closed-sleeve treatments, suggesting that predation is likely limiting the establishment success of this strain. In addition, we noted that daily maximum temperatures at our field sites might exceed documented developmental thresholds for this strain, and that MaxEnt species distribution modeling indicates no climate similarities between locations in eastern North America and Kyushu. Combined with previous results, our study suggests that the establishment of the Kyushu strain of A. itadori as a biological control agent for Japanese knotweed may be limited in eastern North America. We suggest that one strategy to increase the probability of establishment of the Kyushu strain could be to increase the number of release sites in an effort to find a more optimal niche with predator-free space.
薇甘菊属（荨麻目：蓼科）的薇甘菊物种，包括日本薇甘菊（R. japonica Houtt.），是引入北美和欧洲的最具入侵性和生态破坏性的植物物种之一。Aphalara itadori Shinji（半翅目：蚜科）九州株已被批准作为生物防治剂，在英国、加拿大和美国释放，以防治日本薇甘菊。然而，最近来自加拿大的报告表明，生物和非生物因素都可能限制其建立。因此，我们通过比较开放和封闭套处理，以及通过从释放地点收集温度数据并使用 MaxEnt 进行气候适宜性分析，来检查捕食的潜在作用。我们的结果表明，九州株的种群只能在封闭套处理的野外维持，这表明捕食可能限制了该菌株的建立成功率。此外，我们注意到，我们的野外地点的日最高温度可能超过了该菌株的有记录的发育阈值，并且 MaxEnt 物种分布模型表明，北美东部和九州之间没有气候相似性。结合以前的结果，我们的研究表明，作为日本薇甘菊的生物防治剂，九州株的 A. itadori 的建立可能在北美东部受到限制。我们建议，增加九州株释放点的数量，以找到一个没有捕食者的更理想的小生境，这可能是增加建立概率的一种策略。
