Key Features
- Leaf spots
- Black stem cankers
- Defoliation
Symptoms
Boxwood blight begins with the appearance of brown leaf spots that lead to defoliation. Eventually, black streaking appears on stems. The rarely used shrub, sweetbox (Sarcococca spp.), along with ground covers Japanese spurge (Pachysandra terminalis) and Allegheny spurge (P. procumbens) are also susceptible to boxwood blight.
Biology
Unlike other diseases of boxwood, excessive defoliation is often associated with box blight and often occurs first on the shadier side of the plant, closest to the ground where leaves stay wetter for longer
Management Recommendations
The boxwood varieties B. microphylla ‘Golden Dream’, B. harlandii, B. sinica var. insularis ‘Nana’ and B. microphylla var. japonica ‘Green Beauty' are the most resistant varieties. Highly susceptible boxwoods like 'Suffruticosa' and 'Justin Brouwers' should be avoided, or removed if the disease becomes established. Chlorothalonil can be used to protect high value plants, but applications need to be season long on those highly susceptible varieties.
Effective Pesticides
Pesticides are neither available nor recommended for managing this disease.
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
