Wednesday, March 28, 2012

Next up: Boxwood Blight - Invasive Species Impact Everyone

               The rapid expansion of the number of invasive species causing harm to existing ecosystem services and resources should be cause for some modicum of attention even if not alarm. The gardening industry is mostly dismissive of the impact of invasive species unles and until they affect ornamental horticulture, at which time there is a focus on the organisum causing the problem not the problem as a while. Soit is that fast on the heels )legs) of the marmorated stink bug[1] comes a new disease that attacks one of the mainstays of the garden landscape, the boxwood, or as some call it, the box.
               The new disease is referred to now as box blight,  Cylindrocladium pseudonaviculatum (synonym: Cylindrocladium buxicola). The disease has only been observed on leaves and shoots of Buxus spp. in nature. As with most exotic, alien,, novel,  introduced species,  full host range of this species is not fully known. And to make things more interesting, there appears to be no published evidence of resistance to this fungus in the many commercially available  boxwood species. The invasive species attacks both the non native, English boxwood, (Buxus semperviens ‘Suffruticosa’ ), as well as the non-native American box, Buxus sempervienand Korean box, Buxus microphylla var. koreana.  Controlled laboratory test show that the fungus can attack other species in the boxwood family such as Sarcococca and Pachysandra. [2]
               According to the Maryland Home and Garden Center,
               "Box Blight or Boxwood Blight has been causing defoliation of boxwoods throughout Europe since the late 1990’s. In October, 2011, the disease was found in North Carolina and Connecticut in both nursery, and landscape plantings. The disease was also found in a Virginia nursery. Since this first US report the disease has been identified in a number of northeastern states and also in Oregon, and British Columbia. The first Maryland case of Boxwood Blight was confirmed on plants from a landscaper’s nursery in December, 2011. The first symptoms begin as leaf spots followed by rapid browning and leaf drop starting on the lower branches and moving upward in the canopy."
               "The key symptoms that differentiate Boxwood Blight from other boxwood diseases, such as Volutella Blight and Macrophoma Leaf Spot, are numerous narrow black cankers (black streaks) that develop on the green stems.  The pathogen does not attack the roots, so larger plants may produce new leaves during the growing season, but may lose ornamental value as defoliation becomes severe. Repeated defoliation and dieback from stem cankers has killed small rooted cuttings in nursery propagation. The causal fungus can remain in alive in fallen leaves which can then serve as the source of infection for subsequent years."[3]
               The continuing introduction, establishment and spread of species that have not developed interactions and relationships with indigenous species is causing major shifts in the expected services and resources of our ecosystems. We depended on these ecosystems to clean the water, control its movement, supply refugia for diversity, supply our food, feed, fiber, forage, flower, fish and forest needs as well as to create an landscape hospital to our human psychological desires. And most of us see not problem in the slow fire of ecological destruction and resource disturbance because it is happening at a rate of change that is slower than our current news cycle. By the time we see an invasive species problem; by the time it reaches out and directly impacts us individually, the cost of recovery is beyond our reach and we are in adaptation mode at best. 

[1] Thompson, John Peter. Stink bug species invades our space. September 18, 2010. [accessed March 28, 2012]
[2] USDA-APHIS-PPQ-CPHST and NCSU-Department of Plant Pathology, Mountain Horticultural Crops Research and Extension Center (MHCREC). The ‘box blight’ pathogen: Cylindrocladium pseudonaviculatum = Cylindrocladium buxicola (Teleo. Calonectria pseudonaviculata). [accessed March 28, 2012]
[3] Maryland Home and Garden Information Center. Box Blight.  [accessed March 28, 2012]

1 comment:

TheLocalScoop said...

Buxus spp. native to America? Not continental N. America according to the USDA plant database ( If they are non-native and dying off, there's an opportunity for native shrubs(native Spirea spp. or viburnum spp., etc.)to be planted instead.