boxwood  pseudonectria canker symptoms

Branch dieback and leaves turning from green to brown (Pseudonectria rouselliana). Photo: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org

Updated: April 21, 2021
Volutella stem blight or canker of boxwood
Both American and English boxwood are susceptible to Volutella

Key points

  • Both American and English boxwood are susceptible to this disease caused by the fungus, Pseudonectria rouselliana. The imperfect stage is Volutella buxi.
  • Before new growth appears in the spring, leaves on the tips of infected branches turn red, then bronze and finally yellow. Infected branches die back.
  • Examination of affected branches reveals loose bark and girdling at varying distances from the tips and discoloration of the wood.
  • In moist weather the fungus produces salmon pink fruiting bodies on leaves and stems.

Management

  • Diseased branches should be pruned out and when the foliage is dry.
  • An important measure to help prevent and control Volutella is thinning (instead of shearing) boxwood to improve air circulation and light penetration. Thinning is a type of pruning that removes interior stems.
  • Old fallen leaves and diseased leaves that have accumulated in the crotches of branches in the interior of the plant should be shaken out and removed.
  • Improve growing conditions, especially to alleviate drought stress.