Niche partitioning and coexistence of parasitoids of the same feeding guild introduced for biological control of an invasive forest pest

When multiple species of host-specific natural enemies from the same feeding guild are introduced to areas against a target pest, strong interspecific competition is likely and may compromise biocontrol unless agents effectively partition available resources. Here, we evaluate if two parasitoids (Spathius galinae Tetrastichus planipennisi), for invasive emerald ash borer (EAB), Agrilus planipennis, into North America have established niche-partitioning, co-existing populations following their sequential or simultaneous field releases 12 hard-wood forests located in Midwest Northeast regions United States. We found recently EAB larval parasitoids, S. T. planipennisi, all release areas. Presence, abundance, and/or host attack (parasitism) rates parasitoid differed significantly among tree-size classes, with parasitism more abundant larger diameter pole-size trees, while planipennisi dominated saplings. also abundance larvae declined height both saplings whereas broods was unaffected. However, strongly positively correlated sampled sections preferred classes. Our findings suggest that specialist complement one another protecting trees different size classes EAB.