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Boxwood Blight

Cylindrocladium pseudonaviculatum (syn. C. buxicola)


Synonyms

  • box blight
  • boxwood leaf drop
  • Calonectria pseudonaviculata (teleomorph)

Plant hosts

Buxus species, Sarcococca species, and Pachysandra species


Symptoms

      Symptoms of leaf blight                        Symptoms of stem blight

Symptoms on boxwood include light or dark brown circular leaf spotting and black longitudinal or diamond shaped lesions on stems.  Progression of the disease results in defoliation of leaves and an overall straw colored appearance of the plant.  Disease transmission is increased in moist environments, making host plants in greenhouses particularly susceptible.  Boxwood blight has a rapid disease cycle that can be completed in one week.  The fungus can form resting structures (chlamydospores and microsclerotia) that can survive for five or more years on host organic debris in the soil.  Mortality most often occurs in seedlings, but may also take place in older plants, especially if infected with a secondary pathogen. This disease may be confused with Volutella leaf and stem blight, a common disease on boxwood in Oregon.


Transmission

The boxwood blight pathogen produces spores in a sticky, slimy matrix when environmental conditions are suitable.  The spores are splash-dispersed and can be carried by wind or wind-driven rain over short distances.  Long distance spread is thought to occur primarily through infected plant material and water (rain splash, irrigation, runoff, etc...) but can also be dispersed by human activities (contaminated boots, clothing , pruning tools, and equipment), animals, and birds.


Geographic distribution

Boxwood blight has been reported throughout Europe, the United Kingdom, and New Zealand and in the United States in Connecticut, Maryland, Massachusetts, North Carolina, Oregon, Pennsylvania, Rhode Island and Virginia.


Applicable regulations

At this time there are no regulations.  There is a voluntary Nursery Cleanliness Program for Boxwood Blight.


Aditional links

Nurseries participating in the Nursery Cleanliness Program for Boxwood Blight.