Boxwood Blight

— Written By Peg Godwin and last updated by
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Boxwood blight is a devastating disease causing rapid defoliation and unsightly plants. The pathogen has been found to survive in leaf debris placed either on the soil surface or buried in the soil for up to 5 years.

Boxwood blight has been a problem in North Carolina since it was first found here in the fall of 2011. At first it was primarily a problem for the nursery industry, but it has been found in an increasing number of landscapes across the state. Boxwood blight has recently been confirmed in plant material from Kinston by testing at NCSU Plant Disease and Insect Clinic.

Affected boxwood show three main symptoms: dark leaf spots, dark streaks on green twigs, and leaf drop. In some cases, leaves will lose their luster and dry up without the typical spots, but this can happen for reasons other than boxwood blight. American and English boxwoods are particularly susceptible and are rendered unsightly by the disease, although they do not die. Sarcoccoca (sweet box) is also affected. The fungus can infect Pachysandra, too, causing leaf spots that could go unnoticed.

Boxwood blight is caused by a fungus known scientifically as Calonectria pseudonaviculata. It also goes by the names Cylindrocladium pseudonaviculata and Cylindrocladium buxicola. The fungus is harmless to other kinds of plants, to animals, and to people. Calonectria pseudonaviculata can be spread long distances on infected plant material and could be moved on contaminated clothing, bags, footwear, tools, vehicles, etc. used by workers moving from field to field. Short-distance spread is by splashing water and potentially by animal activity. The sticky spores do not easily become airborne except by water splash.

According to NCDA&CS plant pathologist Leah Roberts, there are widespread reports of boxwood blight on holiday greenery being sold at retail outlets. Checking your greenery could help you avoid irreversible damage to established landscape plants. Infected wreaths and roping that are exposed to rains could be a source of the fungus for nearby boxwood, sweet box, or Pachysandra. Greenery that is hanging in a sheltered area will pose little immediate risk, but leaves falling from them could be a source of contamination later on.

What should you do if you have boxwood greenery for the holidays? As a precaution, we are recommending the following:
(1) Inspect boxwood greenery for blight, and immediately discard suspicious material, including fallen leaves.
(2) If there are boxwood shrubs in your landscape and if any boxwood greenery has been placed in an area where it is exposed to rainfall, relocate the greenery or bag and discard it. Do not handle the material when wet, because you could easily spread the spores.
(3) At the end of the holiday season, bag up all boxwood greenery and dispose of it in a landfill. Do not place it in the compost.
(4) Monitor nearby boxwood plantings for symptoms of the disease.

For more information go to the Virginia Boxwood Blight Task Force web page http://www.pubs.ext.vt.edu/PPWS/PPWS-29/PPWS-29.html. It has good references and includes lists of best management practices for different situations. Information in this article has come from Virginia Cooperative Extension and NCSU PDIC blog.