Submitted photo | Dr. Kelly Ivors
This pictures shows what a young boxwood infected with the fungus Cylindroclaidium buxicola looks like. The two most commonly planted cultivars in the United States, the American boxwood and the English boxwood, are most susceptible to the highly infectious disease.
Submitted photo | Dr. Kelly Ivors
This photo shows how a plant infected with boxwood blight loses foliage from the ground up. Other symptoms of the highly infectious disease include brown and purple lesions on the leaves and black lines on the stems.
Local boxwood growers are keeping a wary eye out for a boxwood blight new to the United States as North Carolina State scientists work to offer alternatives to stop the spread of the fungus.
“People need to be aware,” said Karen McIsaac, owner of Angels’ Floral and Gift Farm LLC. “Persons need to be pro-active and know how to recognize this fungus because it is so easily transmitted. It is so new many don’t recognize what it is. They say oh well, the boxwood just died.”
According to McIsaac, if environmental conditions are right the sticky fungus can be transmitted by animals who rub against an infected plant and transfer it to healthy bushes they push against later on. Surry County Cooperative Extension Service Agent Joanna Radford echoed McIsaac’s concerns.
Radford said the blight is very contagious and the only two safe ways of disposing of infected plants are burning them and burying them. She cautioned that all foliage and debris from infected plants carry the fungus and also have to be burned or buried. Gardening tools also should be sterilized in a solution of bleach and water. She said the fungus also can be spread by infected plants that come in contact with water, such as a creek. The water would carry the fungus downstream and contaminate other areas.
She said the boxwood industry in Surry County alone represents a $3 million industry. She confirmed there have been cases of the blight found locally. The entire green industry in North Carolina represents about $8 billion in income yearly.
“The cases we have found are very serious,” said Radford. “We have to be very careful and contain this.”
Radford said infected plants lose leaves from the bottom up at first. Leaves will have brownish purple lesions and stems will have black lines. Plants lose all their leaves in severe cases but often survive and put out leaves the second year. This growth also is contagious.
Rebecca and Clinton Davis of Davis Boxwood and Daylilies in Lowgap are like many local growers who are keeping a wary eye out.
“As far as the blight goes, we have been blessed so far,” said Rebecca Davis. “Extension Agent Joanna Radford came out on our request to check out a dead area on one plant. She sent off a sample and it turned out to be what we thought, just a dead spot hit by the mower.”
A number of local growers said growing conditions had been good, leaving them with healthy plants. Traditionally, this time of the year is when the boxwood season doesn’t see a lot of activity, like its sister industry which produces Christmas trees, wreaths and garlands. The growers’ chores will kick into high gear again after the ground freezes and thaws in spring.
Most growers are optimistic for the season to come because many boxwood were destroyed in the north by Hurricane Sandy and spring could see a surge in demands for the plants.
According to North Carolina State Associate Professor of Plant Pathology Dr. Kelly Ivors, the boxwood has been important to American gardens and landscapes since colonial days. Ivors is among the first of this group of researchers and extension specialists trying to find methods to protect boxwood from the blight.
It was first found and confirmed in the United States in 2011. Ivors is leading a study to determine which commercially available boxwood species are most susceptible and which ones can withstand the fungus, Cylindroclaidium buxicola, which causes the disease.
Her research has garnered support from a greenhouse and nursery industry alarmed by the presence of the disease also referred to as box blight or boxwood leaf drop.
“The reason this is a big deal is because boxwood is grown for its foliage. It is grown as an emphasis or topiary plant in the landscape and so when you have a plant that drops a lot or all of its foliage, it loses its marketability,” said Ivors.
A Virginia nursery, Saunders Brothers Inc., donated 1,600 boxwood plants for the university’s studies while state landscape and nursery associations from North Carolina, Virginia and West Virginia contributed more than $30,000 to build an outdoor containment area. This area is used to conduct tests on the blight. The center is located at the university’s Mountain Horticultural Crops Research and Extension Center in Mills River.
“Not only can the disease quickly take out thousands of plants at a nursery, the fungus can persist in the soil for years. That means that once it’s established, it could be difficult to get rid of,” said Ivors. “So far, the disease has been found in 10 U.S. states and three Canadian provinces.”
Ivors said her findings from the susceptibility research cause concern and optimism.
“On one hand, the two most commonly planted cultivars in the United States, the American boxwood and the English boxwood, are by far the most susceptible,” Ivors explained. “This is because they lose the most amount of foliage when exposed to the fungus.”
She added several of the 23 tested varieties tolerated the fungus and could be suitable replacements for American and English boxwood. These two are mostly found in everyday landscapes as well as gardens in iconic places including the White House, Mount Vernon and Colonial Williamsburg.
Ivors is joined on the study by graduate student Miranda Ganci and Dr. D. Michael Benson, a professor of plant pathology. According to Ivors, N.C. State University researchers are the only ones who’ve conducted experiments outdoors under natural disease conditions.
Finding solutions on how to manage the disease is also on Ivors’ and her colleagues’ agenda. They are analyzing data from research earlier this year on how well various commercially available fungicides work against the disease.
She recommends plants infected with boxwood blight be destroyed. Disease symptoms include dark or light brown circular spots, often with dark edges on the leaves. The disease also can cause dark streaks in stems, straw to bronze colored blighted foliage and the loss of leaves. Young plants are especially at risk of infection but the disease also can affect mature plants.
Homeowners suspicious about their boxwood plants may submit samples to the N.C. State University Plant Disease and Insect Clinic. The testing is free for those who follow rules outlined at http://www.cals.ncsu.edu/plantpath/extension/clinic. More information on the disease, its symptoms and management is available at http://go.ncsu.edu/boxwood_blight_links.
Ivors cautions buyers to make sure varieties they select not only are free of disease symptoms but are suited to plant hardiness zone.
“I don’t want to discourage people from buying boxwood,” said Ivors. “But we need to educate the green industry and their clientele to let them know what boxwood blight looks like so we can limit the disease from becoming established.”
Reach David Broyles at dbroyles@heartlandpublications or 710-1952.
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