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Research Project: Biological Control of Invasive Wood-Boring Insect Pests such as Emerald Ash Borer and Asian Longhorned Beetle

Location: Beneficial Insects Introduction Research Unit

Title: Interspecific competition between idiobiont larval parasitoids of emerald ash borer

item RAGOZZINO, MAX - Virginia Tech
item Duan, Jian
item SALOM, SCOTT - Virginia Tech

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2021
Publication Date: 8/16/2021
Citation: Ragozzino, M., Duan, J.J., Salom, S. 2021. Interspecific competition between idiobiont larval parasitoids of emerald ash borer. Journal of Insect Behavior.

Interpretive Summary: The emerald ash borer (EAB) is a serious invasive forest pest that has killed tens of millions of ash trees in the United States. Two parasitic wasps (Spathius agrili and S. agrili) were introduced from Asia for biological control of EAB in North America. Because these wasps attack the same EAB larval stages, we examined the potential effects of competition on EAB parasitism rates. Competition favored S. agrili over S. galinae, but S. galinae was not entirely excluded. Although competition between adult wasps lowered the parasitism rates by each species, overall parasitism of EAB by both species was not reduced. Because competition between these two wasps does not harm the efficacy of EAB biocontrol, both wasp species can be released together for biocontrol of EAB in the USA.

Technical Abstract: New associations between parasitoid species are common in biological control, and interactions range from coexistence to competitive exclusion. Spathius agrili and Spathius galinae are two host specific idiobiont larval parasitoids of the invasive emerald ash borer Agrilus planipennis which do not overlap in their native ranges. We conducted laboratory experiments to determine the results of competition between these two species. Competition between parasitoid larvae on a single host (intrinsic competition) and competition between adult parasitoids for oviposition sites (extrinsic competition) were evaluated. Multiparasitism never occurred in any trial, and intrinsic competition was determined by exposure order. Extrinsic competition favored S. agrili, but S. galinae was not excluded. Competition lowered parasitism rates for both species, but overall parasitism of EAB was not lowered.