Distribution of Scirtothrips dorsalis cryptic species complex in the United States and true host assessment of its dominant member

Authors: KUMAR, VIVEK - University Of Florida; XIAO, YINGFANG - University Of Florida; BORDEN, MATTHEW - Bartlett Tree Company; Ahmed, Muhammad; McKenzie, Cindy; OSBORNE, LANCE - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2023
Publication Date: 7/19/2023
Citation: Kumar, V., Xiao, Y., Borden, M.A., Ahmed, M.Z., Mckenzie, C.L., Osborne, L. 2023. Distribution of Scirtothrips dorsalis cryptic species complex in the United States and true host assessment of its dominant member. Journal of Economic Entomology. 2023. https://doi.org/10.1093/jee/toad138.
DOI: https://doi.org/10.1093/jee/toad138

Interpretive Summary: Chilli thrips is a devastating pest belonging to a cryptic species complex (Scirtothrips dorsalis Hood) with nine distinct species that look the same morphological, but differ biologically (host range, resistance to insecticides) and genetically. The complex attacks ornamental and vegetable crops from at least 50 plant taxa in the United States. In an attempt to develop a knowledge-based management program for invasive thrips in horticulture production, we assessed the geographical and host range of two members of the S. dorsalis species complex that recently invaded the US. The current study demonstrates South Asia 1 is highly invasive and the dominant member of this pest complex with a well-established population in the southern and western US, whereas East Asia 1 is endemic to northeastern states and slowly expanding its boundaries. South Asia 1 is adapted to a wider host range and poses a serious threat to the horticulture industry. The outcomes from this study will help residents, growers, researchers, educators, and extension personnel combat S. dorsalis effectively and contain its invasion into a new region.

Technical Abstract: Scirtothrips dorsalis Hood is a cryptic species complex of at least nine distinct species, and two of which (South Asia 1 and East Asia 1) have been confirmed damaging >50 plant taxa in the United States. To develop a knowledge-based management program for this pest in the US, the objective of the study was to i) survey for Scirtothrips dorsalis, species complex in the suspected regions, and ii) assess the true hosts (reproductive + feeding) of the predominant member available. Researchers, extension personnel, and growers from all the regions reported to exhibit S. dorsalis or its symptomology, were contacted to provide thrips from resident populations. Thrips samples obtained were subjected to taxonomic and molecular characterization. Out of the 101 thrips populations received across the US over a six year period (2015-2021), 71 were confirmed as S. dorsalis, and ~44% of those populations were identified as South Asia 1, suggesting this species is more prevalent in the US compared to another counterpart East Asia 1, which was primarily found in samples collected overtime from hydrangea (95%) in Massachusetts, New York, and Pennsylvania indicating this species is expanding its geographic range in the northeast and has the capability to overwinter in areas that experience hard freezes. While assessing the true host range of South Asia 1 (dominant species), 62 plant taxa were evaluated under greenhouse conditions. Among these, 40 feeding and reproductive hosts were confirmed in Florida. We also found 17 new true hosts and four feeding hosts of S. dorsalis, which were not previously reported in the literature, indicating the host range of this pest continues to expand after invading into the New World. Results of the study provide insight in the increasing host range and expanded geographical distribution of S. dorsalis species and will enable the development of a species-specific management program.