Beware of Boxwood Blight

by Jessica Neese

There has been a lot of chatter in the landscape industry since Boxwood Blight was confirmed in Georgia in 2013. Although only a handful of cases have been confirmed in the Atlanta area, professionals are taking this threat seriously in hopes that the spread of the blight can be contained and prevented from becoming an established pathogen. The key to protecting the legacy of Boxwood lies with educating professionals in the industry and gardeners in our communities.

About Boxwood
Chances are you have Boxwood in your landscape; they are an integral part of American landscape architecture history. They were first introduced to the United States in the mid 1600s when they were brought over from Amsterdam. The largest collections in the United States can be found in the Virginia State Arboretum and the U.S. National Arboretum in Washington, D.C. Boxwood are primarily found in landscapes along the Atlantic and the Northwest Pacific states. There are more than 200 cultivars of boxwood which extend their uses in landscapes as stand-alone specimens, groupings, hedges, parterre gardens, bonsai, and topiaries. Traditionally used in classic and formal garden settings, it’s not unusual to see them these days in contemporary and modern landscapes.

Nine Need-to-Knows
Boxwood Blight is a fungus that was discovered in Europe in the mid 1990s. This blight was not confirmed in the U.S. until 2011. Currently confirmed in 10 states, Boxwood Blight is caused by the fungus Cylindrocladium pseudonaviculatum. Here are some things you need to know about the blight:
1. The first symptoms appear as circular tan leaf spots with dark borders along with blackening of the stems.
2. Rapid defoliation can also be a symptom.
3. The blight can be confused with Volutella blight and other root stresses or diseases. This blight favors warm (not hot) and humid conditions.
4. Shadier areas tend to experience more rapid disease development.
5. Different varieties have shown varying susceptibility.
6. English boxwood are highly susceptible and show severe symptoms of rapid leaf drop. American boxwood are susceptible.
7. Asian varieties such as the Korean Wintergreen boxwood are less susceptible and do not demonstrate severe symptoms and leaf drop.
8. There are no known cures for the blight, but preventative fungicides have been successful in preventing infection.
9. The blight spreads very quickly and is spread by contaminated plants and plant debris.

What You Can Do
The best practice to prevent the spread of this blight is to engage with professionals who are committed to Safe Management Practices to help eliminate cross contamination. Plant material should be purchased from nurseries who are members of boxwood blight prevention programs. Most boxwoods in Georgia are supplied by nurseries in North Carolina. The North Carolina Department of Agriculture has a voluntary Boxwood Blight Compliance program that the most reputable growers are members. Local plant brokers and landscapers should adopt the following practices:
1. Purchase boxwood from an exclusive vendor so that problems can be isolated
2. Separate boxwood from other plant material and restrict employee/customer access
3. Disinfect tools in contact with boxwood with Lysol or a 10% bleach solution
4. No plant material can be returned to a nursery from a job site
5. Live plant inspections from the Department of Agriculture
6. Train employees to identify this blight
7. Avoid overwatering and pruning wet plant material.
8. Report suspected blight to a professional. University of Georgia’s Plant Disease Clinic can test samples.

Boxwood are a staple in landscape architecture. It’s not the time to give up and move on from the backbone of Southern gardens. Europeans have successfully managed the blight for a decade and Georgians have the opportunity to get ahead of this potential threat.

Jessica Neese is a principal at In Bloom, a local landscaping company.
For more information, visit InBloomLandscaping.com or call 404.373.0023.

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