Differences in early season emergence and reproductive activity between Spathius agrili (Hymenoptera: Braconidae) and Spathius galinae, larval parasitoids of the invasive emerald ash borer (Coleoptera: Buprestidae)

Authors: RAGOZZINO, MAX - Virginia Tech; MEYER, RYAN - Virginia Tech; Duan, Jian; SALOM, SCOTT - Virginia Tech

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2019
Publication Date: 4/17/2020
Citation: Ragozzino, M., Meyer, R., Duan, J.J., Salom, S. 2020. Differences in early season emergence and reproductive activity between Spathius agrili (Hymenoptera: Braconidae) and Spathius galinae, larval parasitoids of the invasive emerald ash borer (Coleoptera: Buprestidae). Environmental Entomology. 49:334-341. https://doi.org/10.1093/ee/nvz168.
DOI: https://doi.org/10.1093/ee/nvz168

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, including mid-Atlantic states such as Virginia. A classical biological control program through the introduction and establishment of co-evolved natural enemies from the native range of EAB (northeast Asia) can be an extremely cost-effective, sustainable, and environmentally benign tool for management of this pest. Two parasitic wasps were introduced from Asia for biological control of EAB in North America. Spathius agrili is native to northeastern China and S. galinae comes from a more northern, colder climate in the Russian Far East. Their different origins may result in different abilities to adapt to climate and to EAB in North America. We conducted field and laboratory experiments to investigate the synchronization of these natural enemies to EAB in the U.S. The two species differed in timing of emergence and fecundity. The Russian wasp produced fewer progeny and emerged sooner than the Chinese wasp under typical climatic conditions in Virginia, which suggests the presence of adults of the Russian wasp and the presence of suitable EAB larvae to attack may not be well-synchronized in Virginia. In contrast, the Chinese wasp may be more suitable for biocontrol of EAB in Virginia.

Technical Abstract: Spathius agrili and S. galinae are host-specific parasitic wasps introduced for biological control of emerald ash borer in North America. Spathius agrili is native to northeastern China and S. galinae comes from a more northern, colder climate in the Russian Far East. Their source of origin may result in different abilities to adapt to climate and their host in North America. We conducted field and laboratory experiments to determine what factors could affect the synchronization of the each parasitioid species to their host in the U.S. Cold-treatments prior to parasitoid emergence were employed to simulate late winter climate conditions in northern and southern U.S. Field populations of naturally infested emerald ash borer were sampled in Virginia throughout the experiment to determine when the parasitoid-susceptable life stage occurred. Cold-treatment did not impact the parasitism rate of either species, nor did it have a multigenerational effect on reproduction. However, the two species did differ in emergence timing and fecundity. S. galinae produced fewer progeny overall, and under warm pre-release conditions emerged sooner than S. agrili. These findings sugest there may be asynchrony between the presence of S. galinae adults and the presence of 3rd-4th instar EAB larvae in Virginia.