Assessing the Potential of Tortistilus (Hemiptera: Membracidae) from Northern California Vineyards as Vector Candidates of Grapevine Red Blotch Virus

Ceresini treehoppers are present in northern California vineyard ecosystems, including the closely related <i>Spissistilus</i> and <i>Tortistilus</i> (Hemiptera: Membracidae). These membracids are not direct pests of wine grapes, but <i>S. festinus</i> is a vector of grapevine red blotch virus (GRBV). No information is available on the ability of <i>Tortistilus</i> spp. to transmit GRBV. In this study, <i>Tortistilus</i> were collected on yellow panel cards across 102 vineyard sites and surrounding areas in Napa Valley, California, USA in 2021-2023. Specimens were morphotyped, sexed and tested for GRBV ingestion and acquisition by multiplex PCR or qPCR. Phylogenetic analysis of the partial sequence of mt-COI and ITS gene fragments of a subset of 40 <i>Tortistilus</i> specimens revealed clustering in a monophyletic clade with <i>T. wickhami</i> with the former barcode sequence. Only 6% (48/758) of the <i>T. wickhami</i> tested positive for GRBV, but none of the heads with salivary glands (0%, 0/50) of the dissected specimens tested positive for GRBV, indicating no virus acquisition. In contrast, half of the dissected heads with salivary glands of <i>S. festinus</i> (52%, 12/23), from the same collection vineyard sites, tested positive for GRBV. Together, our findings confirmed the presence of <i>T. wickhami</i> in northern California vineyards and suggested a dubious role of this treehopper as a vector of GRBV.