Until last summer most people in Maryland weren’t aware of the new fungal disease infecting boxwood called boxwood blight. In 2011 professionals in the green (landscape and greenhouse) industry were informed of the disease but the outbreaks were scattered and insignificant. However, the rainy 2018 season greatly increased the spread of the disease. It has now become more noticeable in Maryland landscapes. In addition, on a few occasions, it has been observed on Japanese spurge (Pachysandra terminalis) in Connecticut and on sweetbox (Sarcococca sp.) in Maryland and Virginia. Essentially, boxwood blight occurs up and down the east coast.
Boxwood blight will infect all boxwoods grown in landscapes. However, some cultivars, especially English and American, are more susceptible than others. See the following photos for symptoms of boxwood blight.
So the question is what to do if your shrubs are diagnosed with boxwood blight? The best information for homeowner action is located on the Virginia Boxwood Blight Task Force website: Best Management Practices for Boxwood Blight.
Here is a quick summary of what to do in the landscape:
- A strong suggestion is to avoid planting any new boxwood plants in your existing landscape or bringing in boxwood greenery, including holiday boxwood wreaths.
- If planting, inspect your plants carefully and ask if the plants have been raised in a certified “cleanliness program.”
- Observe and watch any newly planted boxwoods carefully for disease symptoms.
- Send photos of suspicious symptoms to the Home & Garden Information Center’s Ask Extension service.
- If disease symptoms are diagnosed, immediately bag and remove infected plants along with fallen leaves. Mulch the area to bury remaining debris. Do not compost infected boxwood material. Launder all clothing, gloves, and shoes, and sanitize gardening tools. Removal will not guarantee eradication of the boxwood blight pathogen since it can survive in resting structures in the soil for many years.
- Fungicide sprays have shown some disease suppression in limited situations. However, these treatments do not eradicate boxwood blight and need repeated applications throughout the growing season.
- Consider replacement of boxwoods with non-susceptible plants such as hollies and conifers.
By Dr. Dave Clement, Principal Agent, University of Maryland Extension, Home & Garden Information Center.