Boxwood Blight Diagnosed in Virginia Landscapes in 2016
September 2016 Plant Disease Advisory
We reported on boxwood blight, caused by the fungus Calonectria pseudonaviculata, several years ago after the disease was first found in Virginia in 2011. This disease can be devastating to susceptible boxwood, causing severe defoliation under weather conditions favorable to the disease. Introduction of infected boxwood to landscapes can cause rapid defoliation of established susceptible boxwood. English and American boxwood are highly susceptible to the disease. Spores of the causal fungus do not spread easily by air currents, and until this summer, cases of the disease were rare in Virginia. The main method of disease transmission is by movement of infected boxwood plants. Following the sale of infected boxwood by one national retailer in fall of 2015 and spring of 2016, many cases of boxwood blight have been diagnosed in Virginia landscapes by the Virginia Tech Plant Disease Clinic. Be aware of the risk to existing landscape boxwood when purchasing new boxwood plants.
We strongly recommend purchasing boxwood plants from retailers who exclusively sell boxwood produced by a nursery participating in the Boxwood Blight Cleanliness Program. These nurseries implement best management practices to avoid introduction of boxwood blight-infected plants to their nurseries and are subject to additional inspections by the Virginia Department of Agriculture and Consumer Services.
Also be aware that the disease can be spread on landscape tools. Make sure that landscapers who work in your boxwoods are taking steps to prevent spread of the disease by cleaning equipment and sanitizing tools between landscapes. If your boxwood plants develop symptoms of leaf spots, black streaks on green stems and/or rapid defoliation, double-bag several symptomatic stems that still have some green leaves attached in sealable plastic bags and submit them to your local Virginia Cooperative Extension office. The Extension office will forward your samples to the Virginia Tech Plant Disease Clinic for diagnosis. For more information on this disease, including best management practices and a list of boxwood blight-resistant cultivars, please visit the Virginia Boxwood Blight Task Force web site at: http://www.ext.vt.edu/topics/agriculture/commercial-horticulture/boxwood-blight/.