WILLIAMSBURG — The Colonial Williamsburg Foundation is making efforts to prevent the spread of the boxwood blight disease that has been found in and around their gardens.
The virus is a type of fungal infection known to make the evergreen shrub lose its leaves. It also causes black stem lesions to appear on the infected green plant’s stem. Early in the disease development, the boxwood blight pathogen causes circular, tan leaf spots, often with a dark border.
Many of the boxwoods onsite are older than the restoration of Colonial Williamsburg, which took place during the late-1920s to 1930s. There are estimated to be around 8,000 boxwoods in the Colonial Williamsburg Historic Area. They are still heavily featured because the plant fits the colonial time period design.
This is the first year where the boxwood blight was identified in the Colonial Williamsburg Historic Area. However, Colonial Williamsburg has been using preventative sprays ever since the plant disease was first discovered in Williamsburg five years ago. The landscapers use an anti-desiccant that comes in the form of wax. Twice a year the landscapers will spray the plants, and that spray is supposed to protect them for up to four months. One common spray currently in use is Wilt-Pruf.
“The garden where it was first identified had a very extensive case. So all of the boxwoods were removed from that garden,” said Joanne Chapman, the Colonial Williamsburg Foundation’s director of landscape services. “It really just spread throughout. Although some of the plants weren’t showing signs of infection at the time, they still could’ve been infected with the disease. So the recommendation by the experts was to remove everything on a preventative basis.”
Colonial Williamsburg has also been trying a more surgical approach. If the disease is identified early, and if it’s obvious that it is only a small amount, that portion of the garden that has been identified as infected is removed, along with a couple of feet on both sides.
“There are three things that we look for,” said Colonial Williamsburg Landscape Manager Melissa Sharifi. “Defoliation. The plant will rapidly drop leaves and even the green leaves. So we look for defoliation. If a plant has defoliation on it, we look at the stems. If the stems have black streaks on their green stems. The third sign is leaf spots. You get these big classic leaf spots with a black dark center with a tan halo around that center.”
Rapid defoliation is considered the biggest sign of the blight. When landscapers notice these symptoms, they take the removal process very seriously.
“We’re very very careful about sanitation. So, the staff is in Tyvek suits, and they direct report to the sight. In one of our gardens, we removed a large number of plants,” said Chapman. “They built a containment box and used a wood chipper. They cut the shrubs down, they fed them into the wood chipper, the chipper chipped it into this containment box that actually also has a mist system so that it controlled any of the dust that the chipper makes, and then those wood chips and plant chips were taken to an off sight location and then buried. That crew was in there for about a week and a half.”
This process tends to leave behind a lot of leaf litter. The landscapers will then gather the leaf litter and take a torch to it.
“It doesn’t necessarily have to be burnt up, but it has to reach a certain temperature to kill the fungal spores,” said Chapman. “We have a very large collection here to protect. It’s actually probably the largest in the country. So we are doing our very best to try and protect it as best we can. ”
The boxwood blight pathogen is most active at temperatures between sixty-four to seventy-seven degrees, but it can survive and grow outside of that temperature range. Additionally, the trunk is not infected nor are the roots. This is considered a disease isolated to leaves.
While it is a process that takes time and effort to deal with, it also brings with it many opportunities for Chapman, Sharifi, and their landscaping team to experiment with new preventative techniques.
“It’s an opportunity for education. Hopefully through some of our methods will become useful techniques for other places to use moving down the line,” said Chapman. “It gives us an opportunity to look at some of these gardens.”
For more information on boxwood blight, people can visit Virginia Polytechnic Institute and State University’s Boxwood Blight Task Force website that has been researching and working on the issue in collaboration with the city, William & Mary, and Colonial Williamsburg.
