Quick Summary
- VSD is a newly detected fungal disease in South Carolina affecting redbud, maple, and dogwood trees.
- Symptoms include leaf scorch, interveinal chlorosis, dieback, and brown-to-gray streaking of xylem tissue.
- Infected and symptomatic trees cannot be cured.
- Early detection and sanitation are key to managing this disease.
- Submit suspected plant samples to the PPDC for diagnosis.
In the past five years, a new and destructive disease called vascular streak dieback (VSD) has been observed on commercially produced redbud, maple, and dogwood plants in several states, including TN, VA, and NC. In severe cases, all stock plants affected by VSD were unmarketable.
What Are the Symptoms of VSD?
On these three primary host trees, redbud, maple, and dogwood, symptoms that are characteristic of VSD include:
- Leaf scorch
- Interveinal chlorosis
- Dieback
- Brown-to-gray discoloration (streaking) of the xylem tissue (Figures 1 and 2)
Thereafter, at least 20 more woody ornamental plant species, in both plant production nurseries and landscapes, have been found to be affected by this disease. The causal agent has not been confirmed, but a species of the fungus Ceratobasidium (Ceratobasidium sp. [Csp]) has been consistently detected on trees with characteristic VSD symptoms. The problem has also been diagnosed in additional states – including IN, FL, and OK – and recently confirmed in SC.
Figure 1. Redbud trees at a local SC nursery showing symptoms of leaf scorch, interveinal chlorosis (left), and dieback (right)
Dr. Steve Jeffers, ©Clemson University
Figure 2. Discoloration of xylem tissue (i.e., vascular streaking) in cut shoots (left) and the main stem of redbud trees at a local SC nursery.
Dr. Steve Jeffers, ©Clemson University
Recent Confirmations of VSD in South Carolina
In a collaborative effort among scientists at Clemson University, the Tennessee Department of Agriculture (TDA), and Tennessee State University (TSU), VSD was recently diagnosed at two locations in SC.
Lowcountry Nursery
A redbud sample was collected by a Clemson University Department of Plant Industry survey team from a nursery located in the Lowcountry and was shipped to Tennessee, where Csp was detected by scientists at TDA and TSU.
Upstate Nursery
A group of 10 samples (six redbuds, one dogwood, and three maples) were collected from a nursery located in the Upstate by Dr. Steven Jeffers (Professor of Plant Pathology & Extension Specialist). These samples were processed at the Clemson University Plant and Pest Diagnostic Clinic (PPDC). All redbud and maple samples were diagnosed as positive for VSD based on symptoms and results of an incubation assay (Figure 3), and the diagnoses were confirmed by detecting the putative pathogen Csp using a molecular assay (Figure 4; Drs. Baysal-Gurel and Avin, TSU, personal communication). Only the dogwood sample tested negative, and it did not have typical VSD symptoms.
Figure 3. A redbud sample diagnosed positive for VSD. Three incubated branches had vascular streaking symptoms and growth of Csp mycelium from cut ends of shoots.
Dr. Xiao Yang, ©Clemson University
Figure 4. A molecular assay used to specifically detect Csp. All redbud and maple samples produced DNA bands, indicating positive detection results. The dogwood sample did not produce a DNA band, indicating a negative result.
Dr. Curt Colburn and Dr. Xiao Yang, ©Clemson University
How to Prevent and Manage Vascular Streak Dieback
The confirmation of VSD in SC is unfortunate news for our state’s green industry and ornamental plant nurseries, but there are recommendations that growers can use to help manage the problem.
Prevention is Key
- Good sanitation practices should be followed. Equipment, tools, and production areas should be carefully cleaned before moving between crop groups.
- Carefully scout for VSD-suspected symptoms in both present and incoming plants and isolate any suspect plants immediately.
Early Detection
- If you have plants – especially redbuds, dogwoods, and maples – that are showing VSD-like symptoms, it is important to have them properly diagnosed by submitting samples to the Clemson University PPDC.
- Alternatively, contact Dr. Steve Jeffers if you would like someone to inspect your plants and collect samples.
Fungicides May Help with Prevention
- NOTE: Infected and symptomatic trees cannot be cured.
- Preliminary studies suggest a few fungicide products and programs could help prevent the disease or reduce VSD severity. For more information on current fungicide treatments, see TSU Vascular Streak Dieback: An Emerging Threat to the Redbud Nursery Production in the Southeastern United States.
