Growth of larval agrilus planipennis (Coleoptera: Buprestidae) and fitness of tetrastichus planipennisi (Hymenoptera: Eulophidae) in blue ash (Fraxinus quadrangulata) and green ash (F. pennsylvanica)

Authors: PETERSON, DONNIE - Purdue University; Duan, Jian; YANINEK, STEVE - Purdue University; GINZEL, MATTHEW - Purdue University; SADOF, CLIFFORD - Purdue University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2015
Publication Date: 7/29/2015
Citation: Peterson, D.L., Duan, J.J., Yaninek, S.J., Ginzel, M.D., Sadof, C.S. 2015. Growth of larval agrilus planipennis (Coleoptera: Buprestidae) and fitness of tetrastichus planipennisi (Hymenoptera: Eulophidae) in blue ash (Fraxinus quadrangulata) and green ash (F. pennsylvanica). Environmental Entomology. doi: 10.1093/ee/nvv122.

Interpretive Summary: The emerald ash borer (EAB) has become a serious invasive 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. However, the blue ash (F. quadrangulata) has been more resistant than other North American ash and able to survive EAB infestation. In the present study scientists from the USDA ARS Beneficial Insects Introduction Research Unit and Purdue University investigated how blue ash trees affect the growth of EAB larvae and the fitness of the biocontrol agent (Tetrastichus planipennisi). Findings from this study showed that blue ash trees have no effects on EAB larval growth, nor on the body size and sex ratio of the biocontrol agent, in comparison with susceptible green ash trees. Based on these results, we conclude that increased survival of blue ash is not due to direct effects of the tree on EAB larval growth and mortality. Rather, it the effect is more likely due to the combined effects of non-preference by adult EAB for blue ash and increased exposure to natural enemies. These findings will assist in the development of integrated EAB management strategies that include both host tree resistance and biological control.

Technical Abstract: Emerald ash borer (EAB) (Agrilus planipennis) is a primary pest of North American ash (Fraxinus spp.) trees. Blue ash (F. quadrangulata) is more resistant than other North American ash and able to survive EAB infestation. This tree may affect EAB larvae and T. planipennisi. We compared the capacity of EAB larvae to survive and develop in blue ash and the more susceptible green ash (F. pennsylvanica). Blue and green ash were infested with EAB eggs in the field and laboratory and their bark was peeled to determine larval survivorship and developmental stages. EAB larval survivorship was the same and mortality due to wound periderm formation was low (<4%) in green and blue ash at field sites. Lack of difference in larval mortality in the absence of natural enemies suggests that both green and blue ash can support the development of EAB. However, larvae in blue ash developed more slowly. Nevertheless, parasitism rates by Tetrastichus planipennisi were not significantly different on EAB larvae reared in blue vs. green ash. Moreover, measurements of T. planipennisi fitness including brood size, sex ratio, and adult female size were also unaffected by host. Thus, we conclude that increased survival of blue ash is not due to direct effects of the host on EAB larval mortality. Rather, it is more likely due to the combined effects of non-preference by adult EAB for blue ash and increased exposure to natural enemies.