Suitability of blue ash (fraxinus quadrangulata) and green ash (f. pennsylvanica) to emerald ash borer (agrilus planipennis) and its larval parasitoid tetrastichus planipennisi.

Donnie L Peterson, Purdue University

Abstract

Emerald ash borer (EAB) (Agrilus planipennis) is a primary pest that has killed tens of millions of North American ash (Fraxinus spp.) trees. The larval parasitoid Tetrastichus planipennisi was introduced from China as part of a classical biological control program for long-term EAB management. The high mortality rates of ash trees greatly reduce the number of EAB hosts and may make it difficult for parasitoids to persist. However, blue ash (F. quadrangulata) is relatively resistant and appears to be able to survive EAB infestation. If natural enemies can attack EAB in infested blue ash they may be better able to persist and protect regenerating ash trees. I compared the capacity of EAB larvae and its larval parasitoid to survive and develop in blue ash and the more susceptible green ash (F. pennsylvanica). Blue and green ash trees were infested with EAB eggs in the field and laboratory and their bark was peeled to determine larval survivorship and developmental stages. A subset of blue and green ash was exposed to T. planipennisi so that parasitism rates, brood sizes, sex ratios, and adult sizes could be determined. EAB larvae survivorship was high (>96%) and mortality due to wound periderm formation was low (<4%) on green and blue ash in the field. However, EAB larvae developed slower in blue ash than in green ash in the field and laboratory. In contrast, T. planipennisi brood sizes, sex ratios, and adult female sizes had no significant difference between ash species suggesting that hosts have no apparent affects. In the field, T. planipennisi was able to attack and develop on EAB larvae in caged blue and green ash trees. As such, if T. planipennisi can find blue ash trees, then they should readily attack and survive on living EAB. When joined with higher blue ash survival, it is possible that this ash species could serve as refuge for EAB and its parasitoids after susceptible ash are killed by this pest. Thus, blue ash presence may improve the capacity of parasitoids to parasitize, persist, and protect more susceptible ash species in forests.

Degree

M.S.

Advisors

Yaninek, Purdue University.

Subject Area

Ecology|Entomology|Forestry

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