A suite of Introduced and Native Enemies Reduces Populations of the Emerald Ash Borer
In the United States, high densities of emerald ash borer (EAB) kill ash trees within five years, partly due to the lack of specialized insect natural enemies, or parasitoids, from its native range in Asia. Forest Service researchers collaborated with colleagues in the U.S. Department of Agriculture and university scientists since 2008 to study the impacts of introduced and native parasitoids on EAB populations and ash trees at forested study sites in Michigan. They are finding several introduced and native parasitoids that cause significant larval and egg mortality. To study interactions between parasitoids of EAB larvae, researchers caged different parasitoid species onto small and large infested ash trees. They found that Tetrastichus planipennisi, a relatively small parasitoid of EAB from China, was successful at killing EAB in young, thin-barked ash trees, whereas larger, native parasitoids in the genus Atanycolus were successful at killing EAB larvae in mature, thick-barked ash trees. These findings suggest that these parasitoids will coexist and work together to reduce the population densities of EAB larvae in our ash trees. Researchers continue to study the causes of changes in EAB population densities and the survival of regenerating ash trees at these Michigan study sites.
Forest Service Partners