Devastating boxwood blight discovered in South Carolina
The boxwood blight causal organism, the fungus Cylindrocladium pseudonaviculatum, only attacks the above-ground portions of boxwoods and not the roots. Infected leaves develop light or dark brown spots or lesions. These spots can coalesce and entire leaves turn brown or straw-colored. Eventually the “blighted” leaves drop. Infections on the stems result in dark brown to black lesions or cankers. When these cankers coalesce, the stems become girdled and die. The pathogen survives in diseased tissues—including leaves that have fallen to the ground and cankers on stems that remain attached to the plant. The fungus spreads by splashing water caused by irrigation or rainfall. Pruning also can contribute to movement of the pathogen. Long distance dispersal is facilitated by the transport of infected nursery stock and plant debris. Wind apparently does not aid in dispersal of the spores over long distances.
Photo collage courtesy of: Nicole Ward, UK Cooperative Extension
Just as homeowners prepare for spring, boxwood blight, a fungal disease that can devastate the familiar shrub, has been found for the first time in South Carolina, according to officials with the Department of Plant Industry (DPI) at Clemson University.
The fungus, Cylindrocladium buxicola, was discovered by landscapers near Florence where it had likely been present for several years, said Steven Long, DPI assistant department head.
Boxwood blight attacks the above-ground portions of boxwoods, not the roots. It starts with light or dark brown spots or lesions on infected leaves, but can spread to all foliage and cause the leaves to drop.
It is not a “pest of concern” in South Carolina and therefore is not regulated outside of commercial nurseries. However, it is extremely detrimental to many types of boxwoods and almost always requires plant removal and extensive environmental cleanup, Long said.
“Boxwood blight has not been found in any production nurseries in South Carolina,” he said. “Tracebacks have revealed that the disease most likely hitchhiked here on infested nursery stock from out-of-state nurseries.”
Clemson Extension agents have been advised to be on the lookout for the new disease and to teach landowners and landscapers ways to reduce its spread.
“Boxwood blight can be confused with other boxwood diseases and disorders, but Clemson’s Plant Problem Clinic can analyze plants samples suspected of the disease,” Long said. “If you observe symptoms on your boxwoods, it is important to have the disease accurately identified by a specialist.”
Found throughout Europe, boxwood blight was first discovered in the United States in 2011. It has since spread to 11 states.
The Department of Plant Industry conducts certification and inspection programs related to plant nurseries and enforces state laws and regulations that protect the state from exotic and invasive species.
It is part of Clemson’s Regulatory Services branch, which includes departments that regulate pesticides and structural pest control, verify that fertilizer and lime meet standards and labeled guarantees, conduct seed and organic certification programs, diagnose plant pests and ensure readiness to respond to catastrophic events that impact the state’s agriculture.
