First report of Ceratobasidium sp. associated with vascular streak dieback infecting native plants in an urban forested park in Virginia

Vascular Streak Dieback (VSD) is an emerging problem to the woody ornamental nursery industry in the United States. A Ceratobasidium sp. (Csp) fungus has been detected from over 50 woody host genera exhibiting VSD symptoms, which includes vascular discoloration, interveinal leaf chlorosis, stunting, wilt, and dieback (Bily et al. 2025; Liyanapathiranage et al. 2024). Surveys across the United States have detected Csp from nurseries in 9 states, suggesting long distance spread by the movement of nursery stock (Liyanapathiranage et al. 2025). These detections have exclusively been from plants associated with nurseries or nursery stock planted in the landscape. On 19 May 2025, at Joseph Bryan Park in Richmond, Virginia, a natural stand of young Sassafras albidum plants was observed with stem dieback and discoloration in the xylem tissue (Fig. 1). A 0.25-hectare area around the S. albidum stand was surveyed and 16 symptomatic plants representing 7 host genera were sampled. Approximately 0.1g of discolored xylem tissue from each stem was cut out lengthwise with a sterile scalpel and macerated at room temperature in CD1 buffer for 90 s with a BioSpec MiniBeadbeater-16 (Bartlesville, OK), followed by DNA extraction using the Qiagen DNeasy Plant Pro Kit (Germantown, MD). The internal transcribed spacer (ITS) region was amplified with qPCR using an Applied Biosystems QuantStudio 3 (Waltham, MA) with the Csp-specific CP-qP-Csp primer set (Avin et al. 2025) in three undiluted replicates for each template, and the amplicons were Sanger sequenced at Eurofins Genomics (Louisville, KY). The bidirectional nucleotide sequences were assembled and annotated using Geneious 2023.21 software (Biomatters, Auckland, NZ) and compared to NCBI GenBank sequences with the highest BLASTn identity. Csp was detected from 4 out of 16 plants sampled: from Cercis canadensis (strain VSD25-024/GenBank accession PX210512), Liriodendron tulipifera (VSD25-027/PX210513 and VSD25-028/PX210514), and S. albidum (VSD25-023/PX210511) (Fig. 1). The four 389-392 bp ITS sequences were aligned using MAFFT v. 7.490 (Katoh and Standley 2013) with closely related vouchers from Liyanapathiranage et al. (2024). A maximum likelihood phylogeny using PhyML v. 3.0 (Guidon et al. 2010) placed the sequences in the same clade with verified Csp vouchers RT23-373 (PP663254) from Virginia and FBG6941 (PP458265) from Tennessee (Bily et al. 2025; Liyanapathiranage et al. 2024) (Fig. 2). Due to its fastidious growth and difficulty maintaining a pure culture, Koch’s postulates have not been successful with any plant host, therefore confirmation of pathogenicity on these hosts was not performed (Liyanapathiranage et al. 2024). This is the first record in Virginia of Csp infecting plants not associated with a nursery. Previously, Csp was detected from a Liquidambar styraciflua tree on the wood line of a wholesale nursery in Virginia (Bily et al. 2025). The fungus has also been detected from a Lindera benzoin bush in a natural riparian area in North Carolina (John Bonkowski and Mike Munster, personal communication). Research has shown that Csp-infected C. canadensis plants in nurseries release basidiospores into the air, which may be responsible for localized spread (Liyanapathiranage and Baysal-Gurel 2024). More surveys are needed to understand the impact of this emerging fungus on native plant communities in the eastern United States.