Virginia Cooperative Extension is cautioning the public to take measures to avoid spreading potentially the devastating boxwood blight when decorating for the holidays this year, as clippings in wreaths and garlands have the capacity to spread the disease that could decimate English and American boxwood populations along the East Coast.
Extension, along with boxwood producers, is part of a task force that has formed to educate the public about ways to mitigate the spread of the disease.
Researchers say that boxwood blight could threaten the plants in the same way that the chestnut blight destroyed trees in the 1930s.
“The boxwood is not just a plant. It’s part of Virginia’s cultural heritage,” said Chuanxue Hong, Extension specialist in ornamental horticulture at the Hampton Roads Agricultural Research and Extension Center. “We have moved from trying to contain the disease to managing it.”
In order to help prevent widespread destruction of boxwoods, researchers are asking the public to take precautions when using plant cuttings, pruning existing plants, and maintaining plants at household and historical landscapes.
Boxwood blight is caused by a fungal pathogen that renders the emerald green leaves brown and dry. The fungus can rapidly defoliate boxwood plants, leading to plant death, making the plants unsuitable for commercial sale, and wiping out ornamental landscapes. The disease spreads primarily via infected plant materials and soil from infected plants. This pathogen produces sticky spores that attach to plant containers, tools, vehicles, and shoes and clothes.
Although to date there is no documented case of the disease spreading via clippings, this could be a unique pathway of dissemination for this destructive pathogen. Avoiding visits to infested sites, purchasing and using non-infected plant materials, and practicing strict sanitation methods are crucial to prevent the spread of the disease.
“If boxwood cuttings for holiday greenery were originally taken from infected plants, it is possible they could harbor the fungal pathogen,” said Mary Ann Hansen, instructor and Extension plant pathologist at the Virginia Tech Plant Disease Clinic.
The following simple steps are recommended to mitigate the spread of boxwood blight via holiday clippings:
- If boxwood plants or cuttings are purchased, ask the retailer if the greenery comes from a supplier in the Boxwood Blight Cleanliness Program. Growers in this program adhere to current best management practices.
- Inspect any newly purchased boxwood greenery for symptoms of the disease, including leaf spots, leaf browning, black streaks on stems, and leaf drop. Any greenery that has these symptoms should be double-bagged and discarded in the landfill. Do not compost infected greenery.
- Sanitize pruning tools. In order to disinfect tools, consumers may use the following cleansers: Clorox at 1:10 dilution (or other household bleach that is registered by the Environmental Protection Agency for use as a disinfectant or sanitizer), or Lysol Concentrate Disinfectant (containing chlorophenol, ethanol, and isopropanol). Consumers are reminded to read and follow all label directions when using these products.
- Virginia residents can submit plant samples manifesting symptoms of box blight to the Virginia Tech Plant Disease Clinic through their local county Extension office for diagnosis and control recommendations.
Boxwoods are the mainstays of landscapes in many historical sites across the commonwealth and an important nursery crop. The wholesale market value for boxwood nursery production is $103 million annually.
In an effort to understand the disease and take preemptive measures against the blight, Hong and other Virginia Tech researchers have partnered with North Carolina State University, Rutgers University, the U.S. Department of Agriculture-Agricultural Research Service, Oregon State University, and the U.S. Department of Agriculture Animal and Plant Health Inspection Service-Plant Protection and Quarantine program. Funding comes in part from the USDA.