D3271: Distribution of Scirtothrips dorsalis cryptic species complex in the United States and reproductive host assessment of its dominant member

Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is a cryptic species complex of at least nine species, 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 U.S., the objectives of the study were to i) survey for S. dorsalis species complex in the suspected regions and ii) assess the true hosts (reproductive + feeding) of the predominant member available. Thrips samples received were subjected to morpholo-molecular characterization. Out of the 101 thrips populations received across the U.S. between 2015 and 2021, 71 were confirmed as S. dorsalis, with ~27% further identified as East Asia 1, compared to ~44% identified as South Asia 1, suggesting the latter species is more prevalent in the U.S. East Asia 1 was primarily found in samples collected from Hydrangea sp. (95%) in Massachusetts, New York, and Pennsylvania, indicating geographic range expansion in the Northeast and successful overwintering in areas with 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. The results provide insight into the increasing host range and expanded geographical distribution of S. dorsalis species and will enable the development of a species-specific monitoring and management program.