Historical and current occurrences of EAB in China
To determine the occurrence and distribution of EAB infestations in China over time, we obtained data from field surveys conducted from 2003-2019 in 11 regions of China, including seven provinces (Heilongjiang, Jilin, Liaoning, Hebei, Shandong, Henan, and Sichuan), two municipalities (Beijing and Tianjin) and two autonomous regions (Xinjiang and Guangxi) (Table S1), as well as records from the literature and reports by local faunas about the presence of EAB infestations in each province, provincial city, or region. EAB infestations were defined as areas with large numbers of emerald ash borer causing visible damage or mortality to multiple trees. We considered infestations to be at outbreak levels when emerald ash borer abundance increased in a short period of time resulting in extensive damage to more than 50% of trees. Emerald ash borer was considered present when few trees were attacked at low levels and no damage was reported.
Sample sites for field surveys included: 1) areas within the distribution of EAB with reports of EAB infestations or outbreaks; 2) areas suspected to be within the distribution of EAB with records of EAB presence but no damage reports which required verification by field investigation; and 3) areas with no historical records of EAB presence or infestation. A total of 79 1-ha sample plots were selected. Thirty ash trees were randomly selected in each plot to determine the degree of EAB infestations. When more than 50% of selected ash trees in a plot were found to be infested with EAB, the infestation level was considered to be at outbreak level.
Historical occurrence and distribution of EAB infestations were determined by searching the National Science Data of Forestry (www.lknet.ac.cn/sztsg.htm) with the term “Agrilus planipennisFairmaire” from 1900 to 2019. We found a total of 218 publications of which 17 included details of EAB occurrences, host plant species, and locations in China. These publications were used to retrieve historical data on EAB infestations in China (Supplementary 1). Data retrieved from the publications included the year(s), provinces (provinces, provincial cities, or regions), and cities (prefecture-level cities or districts) of EAB occurrence, infested host plant species and the degree of EAB infestations based on the percentage of infested ash trees. Years of occurrence for each infestation reported in the literature or recorded in field surveys were categorized into six 10-year intervals from 1961 to 2019. The regions of EAB infestations were recorded as provinces, provincial cities, or regions and the exact prefecture-level cities or districts.