Back in the late 2000s and early 2010s, before boxwood blight became a household name among nurseries, growers reported a slump in sales of boxwood and plentiful inventory. This was during the period where the great recession was in full swing and new housing construction was at low levels. Fast-forward a few years, and it’s a whole different story.
The recession ended, and the U.S. real estate market rebounded. Growers now report an inability to meet consumers’ demands for boxwood—a good scenario. Boxwood is the No. 1 woody plant sold in the U.S. In 2014, the USDA National Agricultural Statistics Service estimated the value of U.S. boxwood production at more than $126 million, beating azalea, holly, hydrangea, arborvitae, and many others. Even some greenhouse producers are handling boxwood at certain times of the year.
With demand for boxwood at an all-time high, it’s unfortunate that growers must contend with boxwood blight, the impact of which is increasingly felt in production. The costs to grow boxwood have reached an all-time high as well for most growers.
While other diseases and pests threaten boxwoods—such as boxwood leafminer, Volutella, and mites—boxwood blight, caused by Calonectria
“The American Boxwood Society was overwhelmed at the response to the boxwood blight meeting in Beltsville [Maryland] on Feb. 20, 2018,” says Bennett Saunders, president of ABS. “It is obvious to the society that the industry is very interested in fighting this disease. Indeed, the talks centered on keeping the disease out, but there is an increasing realization that in the future we will manage the disease through better pruning techniques, better groundcover management, more resistant cultivars, and other practices. As this disease becomes better managed, we see a continued strong demand for this ‘Aristocrat of Plants’, in spite of the higher cost of production.”
The spread of boxwood blight
To date, boxwood blight has been positively identified in 25 states. However,
“In any given locality, the fungus that causes boxwood blight is usually moved only short distances, mostly by rain splash, or wind-driven rain…but we help it out in its distribution by inadvertently moving infected plants over large distances via the nursery trade. Diseased boxwood leaves and cankered shoots travel via B&B material, gallon containers, and even in Christmas wreaths,” says Margery Daughtrey, senior extension associate with Cornell University specializing in ornamental plant pathology.
In parts of Europe, where boxwood blight has become almost ubiquitous in production and landscapes, treatment with fungicides is the norm. Eradication is not their primary control
Though boxwood blight was only identified in the U.S. in fall 2011, a tremendous amount of research has been done since then. From 2014 to 2017, USDA APHIS has dedicated more than $2.7 million to boxwood blight research through the Farm Bill, Section 10007. Additional research funds have come from the Floriculture and Nursery Research Initiative program through USDA ARS and the IR-4 Ornamental Horticulture Program with funding from USDA APHIS and USDA NIFA. The Horticultural Research Institute (HRI) sponsors research directly in tandem with its education and advocacy efforts.
Early research efforts focused on fungicide efficacy trials. Since then the research has morphed into the investigation of novel control strategies and longer-term solutions.
Chuan Hong, a professor at Virginia Tech, is coordinating valuable research projects with a “you got questions, we got answers” attitude.
One example is the evaluation of mulch to help prevent spread in landscape situations. The spores of C.
Hong is also working with Len Coop, associate director of the Integrated Plant Protection Center at Oregon State University on
Regarding fungicides, Jim LaMondia, chief scientist at the Connecticut Agricultural Experiment Station, has been testing the efficacy of commercially available products.
LaMondia is also considering the impacts of alternate host plants, such as Pachysandra and Sarcococca, on disease development. Pachysandra production is different than boxwood and is not considered a likely source of boxwood blight. However, Pachysandra can serve as a reservoir for the pathogen in landscape settings.
More ways to help
Sanitation should always be a consideration, regardless of what disease is at play, for both producers and landscape managers. Several products are effective, such as ethanol, bleach, Lysol, and Zerotol. Ethanol, in particular, has been shown to effectively kill C.
Other key research areas include biocontrol options,
Finding tolerant boxwood varieties is a critical need identified by many throughout our industry.
“At Prides Corner Farms we still grow and sell susceptible varieties but have dramatically changed our cultural practices to minimize disease pressure from limited access to the plants, to careful water management and finally to an aggressive chemical program with multiple MOAs,” says Mark Sellew, President of Pride’s Corner Farm. “I believe our industry has to do a better job of policing ourselves, particularly when it comes to growing very susceptible varieties like Buxus
Once boxwood blight was discovered in the U.S, HRI acted quickly and established a fund for boxwood blight research, making some of the first fungicide efficacy trials possible. Since then, HRI has continued support of the industry by leveraging these funds for additional support and the development of
One of HRI’s latest projects is working with researchers toward a standardized protocol where boxwood varieties can be assessed for boxwood blight tolerance. Previous studies have been conducted to evaluate boxwood varieties in terms of tolerance and susceptibility; however, the studies varied in methodology and, in some cases, results. Due to this variability, a more streamlined approach is desired. The boxwood blight research fund was reopened in 2018 and is now accepting donations to help guide the industry towards