Virginia Tech research offers nursery growers relief from devastating boxwood blight
New research could make boxwood, the nation’s top evergreen ornamental shrub, more profitable and easier for growers to manage.
Boxwood blight, a fast-emerging fungal disease that infects one of the country’s most popular ornamental shrubs, has spread to 30 states in the U.S., putting over 95 percent of American boxwood shrub production at high risk.
New research from a team of plant pathologists led by Chuanxue Hong at Virginia Tech’s Hampton Roads Agricultural Research and Extension Center and Jay Pscheidt at Oregon State University suggests that the solution may lie in a fungicide treatment method known as “drenching.” While drenching has been applied to other plants and crops in the past, it hasn't traditionally been used on boxwoods until now. This approach not only drastically reduces the time and cost of treatment for boxwood farmers but also heals infected plants from the inside out.
Drenching involves pouring a solution of fungicide mixed with water onto the soil and around the base of the plant. The traditional method of spraying fungicide directly onto the leaves keeps boxwood blight at bay, but it needs to be applied every couple of weeks, costing farmers valuable time and resources.
“The drench allows the chemistry to be taken up by the roots and transported throughout the plant’s vascular system,” Hong said. “This helps overcome the issue of poor fungicide coverage in boxwoods’ dense canopies. Plus, because the fungicide is internalized, it’s far less likely to be washed away by rain or irrigation.”
The project resulted from research Pscheidt was working on that used AI spraying technology to detect plant canopy density.
“The technology worked fine, but boxwoods are so dense that the spray system doesn’t cover all the places the fungus can spread,” Pscheidt said.
Bennett Saunders, co-owner of Virginia’s largest boxwood producer, Saunders Brothers Inc., said the constant spraying has been one of the biggest challenges he and his brothers have faced since taking charge of the farm in 1980 when they partnered with their father.
“Trying to contain boxwood blight is just as challenging,” Saunders said. "The disease spreads best in wet conditions, so the times when you need to spray the most — right after a storm — are the muddiest to drive a tractor in the fields.”
The brothers have even considered discontinuing boxwood production altogether, but as it accounts for a third of their sales, they need alternatives that protect this vital revenue.
This initiated the fungicide drench studies on boxwood crops, with Oregon State focusing on nursery settings and Virginia Tech on landscape environments.
As drenching dramatically reduces the amount of labor and materials needed to treat infected plants, it may be the solution the Saunderses have been seeking. Rather than applying fungicide 15 times per season, growers only need to drench their plants once at the start of the season.
“Getting coverage all summer, all spring, and all fall — that’s just unheard of,” said Saunders.