Boxwood blight (also known as box blight) is a serious fungal disease of boxwood that results in defoliation and decline of susceptible boxwood. It has been identified in Bedford and we are raising awareness in an effort to minimize its impact. In Virginia boxwood blight was first identified in a nursery location in Carroll County in 2011. By the fall of 2013 it was found in other commercial nursery/retail operations and landscapes in several counties in Virginia. 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.
Virginia Cooperative Extension (VCE) has assembled a Boxwood Task Force. We have developed recommended Best Management Practices for homeowners, landscapers, and plant retailers.
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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. However, there are many disorders that can affect boxwood and the documented incidence of this new blight is minimal to date. Therefore, proper diagnosis is important.
Because the boxwood blight pathogen is not well adapted to long-distance spread by long-distance air currents, the most likely entry point for the disease in a home landscape is by accidental introduction of infected plant material and/or contaminated tools, equipment or other items. Home growers who have boxwood in the landscape should adhere to the following recommendations to avoid inadvertent introduction of this disease to their landscape:
When purchasing boxwood plants for transplanting to a landscape, ask if their boxwood are from producers participating in the Boxwood Blight Cleanliness Program. Production nurseries participating in this program adhere to strict management practices that minimize the chance of introduction of this disease to their nurseries and are inspected by the Virginia Department of Agriculture and Consumer Services (VDACS) for the presence of boxwood blight.
- Prior to purchase, carefully inspect plants for symptoms of boxwood blight.
- Monitor established boxwood and newly planted boxwood on a regular basis for any symptoms of boxwood blight.
- Be aware that boxwood greenery used for holiday decoration could harbor the boxwood blight pathogen.
– To minimize risk of introducing the disease by this route, do not use boxwood greenery near landscape boxwood.
– When disposing holiday greenery, double-bag it in sealed plastic bags and dispose of it in the landfill. Do not compost boxwood greenery.
- The boxwood blight fungus can be spread from one property to another via contaminated spray hoses, pruning tools, wheelbarrows, tarps, vehicles, clothing, shoes, or anything to which the sticky spores of the boxwood blight fungus might adhere.
What to do if boxwood blight is suspected in a landscape
Growers should submit suspect plant samples for diagnosis to the local Extension office (http://www.ext.vt.edu/offices/). We can send samples for confirmatory diagnosis to the Virginia Tech Plant Disease Clinic. The Bedford office is located in the Bedford County Administration Building.
- 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.
- Confirmatory diagnosis of this disease by a plant diagnostic lab is important because other problems on boxwood could be mistaken for boxwood blight. Additionally, to reduce spread of this serious disease, it is important for VCE to know where outbreaks of the disease occur and identify the source of any boxwood blight-diseased plant material.
What to do if boxwood blight is diagnosed in the landscape
Since boxwood blight cannot be effectively controlled once the infection begins, prompt removal of any diseased boxwood is recommended to help prevent spread of disease to healthy plants. Associated leaf debris should also be removed. Be aware that removing diseased boxwood and leaf debris will not eradicate the boxwood blight pathogen from the location, since the pathogen can persist in the soil for 5 to 6 years. These survival structures can infect susceptible replacement boxwood planted in locations where the disease has been diagnosed. Therefore, replanting susceptible boxwood cultivars or members of the Buxaceae family in a location where infected boxwood has been removed is not advisable. Partially resistant boxwood cultivars could be used as replacement plants, but repeated fungicide applications will be necessary to protect any susceptible boxwood cultivars that remain in the land. If you would like more information about this topic, please call the Bedford Extension Office at (540)586-7675, or email the Bedford Extension Master Gardener Help Desk at firstname.lastname@example.org
SOURCE: March 22, 2017 Press Release by Scott M. Baker, Extension Agent, Agriculture