What is boxwood blight?
Boxwood blight is a serious fungal disease that results in defoliation and decline of susceptible boxwood. Once introduced to a landscape, boxwood blight is very difficult and costly to control with fungicides. The major means of spread of this disease is by movement of contaminated plant material (e.g. container or field-grown boxwood, boxwood greenery used for holiday decoration), but boxwood blight spores can also be spread on pruning tools, clothing, equipment and anything that might have contacted infected plants. Home growers can best protect their boxwood by following the measures listed in the Virginia Cooperative Extension publication Best Management Practices for Boxwood Blight in the Virginia Home Landscape.
Symptoms of Boxwood Blight
The most characteristic symptoms of boxwood blight on susceptible boxwood cultivars are brown leaf spots that lead to defoliation and black streaking on boxwood stem tissue. Generally, the black streaking on the stem tissue is indicative of boxwood blight. Other conditions may cause brown leaf spots and defoliation on boxwoods; however, those symptoms seen with the black streaking on the stem indicates the presence of boxwood blight. Some cultivars of boxwood can harbor the boxwood blight pathogen, yet show no symptoms; these cultivars are considered partially resistant (also referred to as “tolerant”) cultivars. Fungicides can also mask symptoms of the disease on susceptible cultivars.
What to do if boxwood blight is suspected in a landscape
Virginia growers should submit suspect plant samples for diagnosis to their local Virginia Cooperative Exten¬sion (VCE) office (http://www.ext.vt.edu/offices/).
• Collect symptomatic boxwood samples (stems with black streaks, leaf spots, or defoliation) and double-bag in sealed plastic bags before transporting to your Extension office.
• Plant samples should be accompanied by a completed plant diagnostic form (456-097), available at the county Extension office.
Download the Virginia Cooperative Extension publication Best Management Practices for Boxwood Blight in the Virginia Home Landscape
Visit the Boxwood Blight Task Force web site
Virginia Cooperative Extension Master Gardener Program and the Virginia Tech Plant Disease Clinic Boxwood Blight Video Series