December: Ho! Ho! Ho! A Plant Health Horror for the Holidays!

As the December holiday season nears, one of the traditions for many folks is to decorate their homes with festive greens.  When selecting wreaths and garlands to using in decorating, keep in mind that you may not only be bringing pine boughs and holly into your home, but also plant pathogens.

Of particular concern has been the boxwood blight fungus (Calonectria pseudonaviculata).  Boxwood blight is a devastating, lethal disease of boxwood, one of our most popular landscape shrubs.  Pachysandra (a common groundcover) is also susceptible to the disease.  Boxwood blight was first identified in the eastern US in 2011 and this past summer was reported for the first time in Wisconsin in a nursery in Kenosha County.  The Wisconsin Department of Agriculture, Trade and Consumer Protection is currently trying to contain and (hopefully) eradicate the infestation.

While the greatest potential for introducing the boxwood blight pathogen into an area is through movement of infected landscape shrubs, there have also been reports in other states (e.g., Indiana) of the pathogen having been found in holiday wreaths festooned with sprigs from infected boxwood shrubs.  These wreaths were produced in North Carolina and then shipped to other states for sale.  The manufacturers unwittingly shipped the boxwood blight pathogen with their wreaths.  A similar scenario could potentially occur in Wisconsin, and if contaminated wreaths are not handled properly, extensive spread of the boxwood blight pathogen could result.

So, what can you do?  First, don’t be afraid to enjoy a holiday wreath; just consider buying one that does not contain boxwood sprigs.  If you are unsure whether a wreath you have already purchased contains boxwood, assume that it does (just to safe) and dispose of it appropriately.  One option is to burn the wreath, if your municipality allows this.  Otherwise, double bag your wreaths in garbage bags, seal them up and place them in your municipal garbage to be landfilled.  Be careful to watch for any leaves or branches that may have fallen from the wreaths and collect these up and dispose of them as well.  In particular, you want to make sure that no potentially contaminated material ends up near boxwood shrubs that you have in your yard.  Under NO circumstances should you attempt to compost any suspect boxwood materials.  Again, if you are uncertain if you are decorating with boxwood, assume that you are and act accordingly.  This is a situation where you can have a huge impact in helping prevent the spread of an economically important disease-causing organism.

If you have questions about boxwood blight (or other plant diseases), feel free to contact the PDDC at (608) 262-2863 or  Also watch for a new University of Wisconsin Garden Facts fact sheet on boxwood blight that should be available on the PDDC website ( early in 2019.  Also feel free to follow the PDDC on Facebook and Twitter @UWPDDC to receive updates on emerging diseases (such as boxwood blight) and their management.