No abstract

Biological invasions are among the most serious threats to native forest ecosystems worldwide due to ever‐increasing international trade and global change. Understanding the invasion processes and ecology of invasive pests in both newly invaded and native habitats is necessary to effectively manage the risks they pose. The emerald ash borer (EAB), Agrilus planipennis, is one of the most devastating invasive forest insect pests in North America and has also invaded European Russia and parts of Europe. Through synthesizing historical data spanning >100 years and contemporary field observations in China, we examined EAB's distribution, occurrence and outbreak frequency in its native range in relation to historical introductions and plantings of non‐Asian ash trees in China. The frequencies and levels of EAB infestations in China gradually increased from 1900 to 2021 after a time‐lag of 30–50 years following introductions and widespread plantings of non‐Asian ash trees from North America. Increased frequencies of EAB outbreaks following the planting of North American ash trees in China may have increased the risk of EAB invading North America and other novel regions. Synthesis. Our findings demonstrated that planting susceptible non‐native host plants can induce outbreaks of a native insect pest in its native range, which, in turn, may enhance risks of invading novel regions via human‐assisted activities (e.g. international trade). In addition, our findings suggest that lag‐times of several decades between planting susceptible hosts and initial pest outbreaks may pose challenges in predicting the true risk of invading novel regions. Consequently, comprehensive risk assessment for invasive insect pests should consider the role of non‐native plants introduced or planted in the pest's native range.

Biological invasions are among the most serious threats to native forest ecosystems worldwide due to ever-increasing global trade and climate change. Understanding invasion processes and the ecology of invasive pests in both newly invaded and native habitats is necessary to effectively mitigate and manage the risks they pose. The effects of exotic ash tree species planted from 1900 to 2019 on distribution, occurrence, and outbreak frequency of a native pest emerald ash borer, Agrilus planipennis Fairmaire, were examined. The frequency and level of pest infestations gradually increased following introduction and widespread plantings of non-native host trees, and the first recorded outbreak occurred after a time lag of 30-50 years. Increased pest populations enhanced its invasion risk to other regions including the native ranges of introduced plants.