Boxwood Blight Information
Boxwoods are a common evergreen shrub planted in home landscapes. Boxwoods tend to be slow-growing plants. Boxwood leaves have smooth edges and are arranged in opposite pairs along the stem. A boxwood plant can survive for decades in the home landscape with minimal maintenance. However, boxwoods are not free from problems. Recently, boxwood blight is a disease that is impacting many homeowners in Forsyth County.
Boxwood blight is a disease caused by the fungus Calonectria pseudonaviculata. Boxwood blight was first diagnosed in North Carolina in 2011 and has been reported in 27 other states. The disease most commonly impacts boxwoods (Buxus spp.), but the fungus can also infect pachysandra (Pachysandra spp.), and sweetbox (Sarcococca spp.). There is no cure for boxwood blight, so infected plants should be removed from the landscape in order to prevent further spread of the disease. Common symptoms of boxwood blight are brown leaf spots that lead to dieback of branches and eventually the entire plant. After dying, the leaves will fall off the stems and sometimes black streaking is visible on the stems.
Proper diagnosis of boxwood blight is essential, as other pests and diseases can damage boxwoods. Other common issues with boxwoods are damage from boxwood leafminer, mites, nematodes, and root rots. If you are suspicious that you have an infected boxwood in your landscape, the only way to confirm boxwood blight is to have a sample of the plant analyzed in a lab – the NC State University Plant Disease and Insect Clinic provides this service to NC residents for a fee. Contact your local Extension office for assistance with submitting a plant sample to the clinic.
If you do have boxwood blight, you need to remove that plant from your landscape. To prevent any further spread of boxwood blight, all boxwood plant material should go to the landfill and not with other vegetative waste. Some structures of the boxwood blight fungus can survive in the soil for 5 to 6 years. It is essential to try to remove all fallen leaves as best you can. You may also wish to cover the area where the diseased plants were with a thick layer of mulch.
The boxwood blight fungus can also spread on pruning tools, clothing, equipment, or other items that come into contact with infected plants. After handling infected plants, be sure to sanitize any tools you used, your clothes and shoes. You can dip tools for 10 seconds in a sanitizing solution. An easy way to clean tools is with a solution of 9 parts water to 1 part bleach. Let your tools dry before storage to prevent rust.
For healthy boxwoods in the landscape, you may wish to apply a preventative fungicide spray. Always follow the label instructions. The recommended fungicides for boxwood blight contain the active ingredient chlorothalonil. Follow the instructions on the label, including guidelines for how often to reapply the fungicide. Most of preventative fungicides for boxwood blight need to be applied every 2 weeks while conditions are favorable for the spread of the disease. This is typically when it is hot and humid. Note that these fungicides protect healthy plants from becoming infected with boxwood blight, but will not cure plants that are already infected with the pathogen.
If you do have boxwood blight, it is best to replace those plants with something else. There are no boxwood varieties that are immune to boxwood blight, but some are more resistant (that information is listed in the publication from Virginia above). Some alternative plants to consider might be:
- Dwarf Yaupon holly – Ilex vomitoria (cultivars ‘Shillings’, ‘Bordeaux’, and ‘Nana’ are all dwarfs)
- Carissa holly
- Japanes Plum yew – Cephalotaxus harringtonia (the ‘Duke Gardens’ cultivar stays fairly small)
There are many other options as well, depending on what you’re looking for in a plant.
For more information about boxwood blight, here are more resources:
- Prevention and Management of Boxwood Blight, N.C. Cooperative Extension
- Best Management Practices for Boxwood Blight in the Home Landscape, Virginia Cooperative Extension
- Virginia Boxwood Blight Task Force
- Boxwood Blight Frequently Asked Questions
- Comparison of Boxwood Blight to Other Boxwood Problems
Reach out to your local office of N.C. Cooperative Extension with further questions.