Boxwood Dieback

Colletotrichum theobromicola

Key Features

  • Blight throughout the canopy
  • Dieback
  • Black stems without defoliation
Attached leaves and dieback consistent with boxwood dieback. Photo by R. Singh.
Black stems are one diagnostic symptom of boxwood dieback. Photo by R. Singh.
Boxwood dieback with lesions spreading in stem. Photo by R. Singh.


Boxwood decline results in random twig dieback, with the foliage remaining attached to the affected branches. Bright black staining occurs under the bark and is present in infected stems.


Boxwood dieback commonly begins through the leaves, with the pathogen spread from plants due to poor pruning practices, and by the dispersal of conidia via rain or irrigation water. This disease is often introduced by new planting stock.

Management Recommendations

Evaluate new plants prior to introducing them into the landscape. Remove infected plants. Preventative applications of fungicides is needed to prevent infection; fungicides will not 'cure' already infected plants.

Effective Pesticides

Active Ingredients include: Chlorothalonil, Thiophanate-methyl


landscape report
Purdue Landscape Report
Plant & Pest Diagnostic Laboratory