First report and integrated analysis of two native Trissolcus species utilizing Bagrada hilaris eggs in California

Authors: GANJISAFFAR, FATEMEH - University Of California; TALAMAS, ELIJAH - Florida Department Of Agriculture; BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL); PERRING, THOMAS - University Of California

Submitted to: Journal of Hymenoptera Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 12/29/2020
Citation: Ganjisaffar, F., Talamas, E., Bon, M., Perring, T. 2020. First report and integrated analysis of two native Trissolcus species utilizing Bagrada hilaris eggs in California. Journal of Hymenoptera Research. 80: 49-70. https://doi.org/10.3897/jhr.80.57024.
DOI: https://doi.org/10.3897/jhr.80.57024

Interpretive Summary: The painted bug (Bagrada hilaris) is a new exotic invasive stink bug that attacks cole crops. It was first reported in southern California in 2008 and since then it has spread throughout the state. Other states where this stink bug is currently found include: Arizona, New Mexico, Nevada, Utah, and Texas. The pest is thought to be native to parts of Africa, Asia and the Middle East. A classical biological control program has started to search for natural enemies to control the pest, especially parasitoids that attack the eggs. As part of this program, field surveys were conducted in California using fresh sentinel eggs of the painted bug to determine what species of natural enemies may already be present. Two of the parasitoids recovered from field looked like native Trissolcus hullensis and Trissolcus utahensis (Hymenoptera: Scelionidae) which were not previously known to be associated with this stink bug. We conducted detailed morphological studies and molecular genetic analysis which confirmed these identifications. This study is one further piece of evidence that B. hilaris eggs may be broadly suitable for Nearctic parasitoids. We conducted surveys in the same locations as Reed and collaborators did monthly samplings of B. hilaris in 2011, and the fact that we did not find any B. hilaris in those areas during our two-year survey, is encouraging as it suggests that populations of B. hilaris have steadily declined in recent years, and it is likely that parasitoids are part of the cause. This study also demonstrates how ongoing parasitoid surveys continue to be productive by providing fresh specimens with host association data that are instrumental for an integrated approach to systematics.

Technical Abstract: Surveys with sentinel eggs of Bagrada hilaris (Hemiptera: Pentatomidae) in southern California retrieved two parasitoids that were not previously known to be associated with this stink bug, Trissolcus hullensis and Trissolcus utahensis (Hymenoptera: Scelionidae). Molecular and morphological analysis of these specimens is used to modify the concept of T. utahensis and assess the factors that contribute to intraspecific variation. We provide an updated couplet to separate T. utahensis from a morphologically similar species, T. cosmopeplae..