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Box Blight

Calonectria pseudonaviculata

6 host plants

Last updated

Data Coverage 3 of 6 dimensions
Causal Agent
Host Plants
Symptoms
Management
GDD Threshold
Regional Notes

Box blight causes leaf spots and stem dieback on boxwood and pachysandra, particularly in wet conditions and poorly ventilated plantings. You'll see dark lesions spreading on foliage and stems. The fungal disease worsens with overhead irrigation and poor air circulation. Control by removing infected plants, improving soil drainage, and spacing plants adequately for airflow.

Remove blighted tissue promptly, cutting well below visible symptoms. Improve air circulation by thinning dense growth. Avoid overhead watering, especially during bloom and new growth periods when tissues are most susceptible. For recurring problems, preventive fungicide applications timed to protect new growth can reduce infection, but cultural controls should be your first approach.

Quick Reference

Causal Agent
Calonectria pseudonaviculata
Host Plants
6

Management

Vulnerability Window

Fungicides are only applied to protect against new infections in the spring during bud break through

Cultural Controls

  • Make certain that the boxwood problem is accurately diagnosed.
  • If box blight is confirmed, destroy infected plants and their debris at the site.
  • Do not compost infected plants.
  • Replant with non-susceptible plants, such as Japanese holly.
  • Space and prune boxwoods to improve air circulation.
  • Disinfect pruning tools.

Host Plants (6)