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Boxwood Blight - Plant Health Concern


A newly discovered boxwood disease is the latest poster child plant pest on the radar screen of plant regulatory officials and industry. Federal officials are in a fact finding mode to determine the extent of spread of Cylindrocladium pseudonaviculatum (buxicola), in U.S. nurseries and landscapes. To date, there have been detections in Connecticut, Maryland, Massachusetts, New York, North Carolina, Oregon, Rhode Island, and Virginia, and the list appears to be growing rapidly. While federal and state regulators have not made any decisions, it is looking as though traditional plant quarantines may be ineffective, and efforts may focus on development of tools and strategies to prevent and manage the disease.
 
Boxwood blight can impact the appearance and aesthetic appeal of its host plant Buxaceae: Buxus colchica, B. microphylla (littleleaf boxwood), B. microphylla var. japonica (Japanese boxwood), B. sempervirens (common boxwood), B. sempervirens 'Suffruticosa' (common boxwood, dwarf cultivar), B. sinica (Korean boxwood), and B. sinica var. insularis (Korean boxwood). The pathogen is known to occur in Europe: Belgium, Croatia, France, Georgia, Germany, Ireland, Italy, the Netherlands, Slovenia, Spain, Switzerland, United Kingdom; and Oceania: New Zealand. A scientific factsheet and other information on boxwood blight are posted at www.ANLA.org.

Updates as of February 3, 2012
Background
–    Pathogen first described in U.K. in mid 1990’s, now throughout most of Europe.  Found in New Zealand in 2002. (Unfortunately, despite published alerts, the U.S. and Canada failed to take protective regulatory measures when they might have had a better chance of succeeding).
–    In U.S., it has now been detected in the states of CT, MA, RI, NY, PA, MD, VA, NC, and OR, and province of BC. In some cases detections have been in nurseries only, in others, in landscape settings.
–    It is a serious disease, appearing to affect most if not all of the commercially important boxwood species and cultivars produced in North America.
–    On a slightly positive note, the blight is NOT a threat to natural/environmental plant resources, or important non-nursery agricultural crops.  It is a nursery and landscape issue.  That said, boxwoods are a major nursery crop and an iconic landscape plant.
 
Regulatory Options
–    Response options are on a continuum.  At one end of spectrum is possibility of federal action to quarantine the pathogen and regulate nursery stock.  At this point, USDA is still evaluating information and options. There is some concern that the disease is too widespread for effective quarantine action.  Some believe that detections would have continued to be made, except for the fact that fall and winter arrived, and that new detections are possible or even likely when the growing season starts.  A federal quarantine has the advantage of establishing a uniform set of rules.
–    Next on the continuum would be no federal action, but a decision by a few, or some, or many states to implement their own quarantines.  State quarantines often lead to a patchwork quilt of differing, even conflicting requirements.  History has shown that it is difficult to coordinate uniform state response, which can have tremendous negative effects on the nursery marketplace.
–    A third option, which has been used for several pests in recent years, is a “management plan” approach where federal officials facilitate a process of convening regulators, industry, and scientists to work through a response plan that is typically less disruptive of commerce than traditional quarantines.   This approach may lead to development/refinement of industry “best practices,” research needs, and control strategies.
–    A fourth option is “do nothing” and allow the marketplace to work it out.
–    At this point, it appears that a management plan approach, or temporary federal action, are the most desirable options.


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