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Title: Natural enemies and their impacts on emerald ash borer populations in its native range, with new records of parasitism by two species of beetles

item WANG, XIAOYI - Chinese Academy Of Forestry
item LIANG-MING, CAO - Chinese Academy Of Forestry
item YANG, ZHONG-QI - Chinese Academy Of Forestry
item Duan, Jian
item GOULD, JULI - Animal And Plant Health Inspection Service (APHIS)
item BAUER, LEAH - Us Forest Service (FS)

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2015
Publication Date: 7/12/2015
Citation: Wang, X., Liang-Ming, C., Yang, Z., Duan, J.J., Gould, J.R., Bauer, L.S. 2015. Natural enemies and their impacts on emerald ash borer populations in its native range, with new records of parasitism by two species of beetles. The Canadian Entomologist. 148(3):329–342.

Interpretive Summary: The emerald ash borer (EAB) has become a devastating forest pest in North America, killing hundreds of millions of native North American ash (Fraxinus spp.) trees since its discovery in Michigan, USA in 2002. The native range of EAB includes large areas of northeast Asia spanning China, the Korean peninsula and the Russian Far East. In order to further explore for potential natural enemies of EAB, we conducted field surveys at several forests within the pest’s native range (north and northeast China) during 2007-2013. Our surveys discovered a complex of natural enemies (eight species of parasitic wasps and two species of parasitic beetles) attacking immature EAB stages (eggs, larvae and/or pupae). However, the relative importance of different natural enemies varied considerably by sampling time and area. The two parasitic beetles were discovered attacking EAB in one of the northeast study sites (Liaoning province); one of them was the dominant species of EAB natural enemies there. The dominant parasitic beetle may be potentially introduced to North America to enhance the efficacy of the current biological control programs against EAB.

Technical Abstract: To investigate the natural enemies of the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), and their role in regulating the pest population dynamics, we conducted field surveys at multiple forest sites with variable host densities in the pest’s native range (north and northeast China) from 2007 to 2013. Field surveys revealed a complex of natural enemies (eight hymenopteran parasitoids and two parasitic coleopterans) attacking immature EAB. EAB eggs and larvae were also attacked by predators (e.g., woodpeckers preyed only on larvae and pupae) and several undetermined mortality factors such as diseases, competition and/or putative plant resistance. Findings from our surveys also indicated that parasitoid complex abundance, as well as its impact on EAB mortality varied with different sampling times and geographic areas in north and northeast China range. For example, the egg parasitoid Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) and the larval parasitoid Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) were not observed in Tianjin, but these two species were frequently observed attacking EAB eggs or larvae in Beijing, Jilin, Liaoning and Heilongjiang whereas Spathius agrili Yang (Hymenoptera: Braconidae) is more prevalent near Beijing and further south in Tianjin). In addition, rates of parasitism are higher later in the season as several of the EAB parasitoids have more than one generation per year. We also discovered two parasitic beetles Tenerus lewisi Lohde (Coleoptera: Cleridae) and Xenoglena quadrisignata Mannerheim (Coleoptera: Trogossitidae) attacking EAB larvae or pupae in one of the northeast provinces (Liaoning), with T. lewisi being a dominant parasitoid of overwintering EAB larvae or pupae there. Together, our findings suggest that classical biocontrol of EAB involving introductions of parasitoids from its native range in China to North America, supports the need to consider the spatial and temporal variations of the natural enemy complex in the EAB’s native range. Further studies are needed to determine whether the two species of parasitic beetles can be potentially used for classical biocontrol introduction against EAB in North America.