Plant Industry - Boxwood Blight

Boxwood Blight

Boxwood blight is a fungal disease of boxwood caused by Calonectria pseudonaviculata which was first detected in North Carolina in 2011. The disease causes severe symptoms including leaf spots, leaf drop, and black stem lesions. Infected plants are unsuitable for sale as ornamentals. No fungicides have been found to have curative effects against the pathogen.

Due to the threat of this disease, many nurserymen have elected to participate in a voluntary compliance program administered by the NCDA&CS Plant Industry Division.

Effective February 4, 2018, Tennessee is establishing an external quarantine against the boxwood blight pathogen, Calonectria pseudonaviculata. North Carolina grower’s wishing to send Buxus sp. and/or Sarcococca sp. to Tennessee will need to be NCDA&CS boxwood blight compliance program participants and will need to have each shipment inspected by an NCDA&CS field representative and an accompanying phytosanitary certificate issued. Christmas wreaths or other greenery containing boxwood are also subject to these new regulations. The full regulations can be read here. Growers should contact their field representative to arrange inspections and contact HT Tseng, Plant Pathologist, with general inquiries at (919) 707-3754.

Compliance program participants agree to follow best management practices specifically developed to prevent and control this very damaging disease. When entering into a boxwood blight compliance agreement, growers are agreeing to:
 

• Require outside workers who enter their fields to dig plants, take cuttings for greenery, 
  or for any other purpose, to follow sanitation procedures. Workers’ clothes, shoes, tools, vehicles, equipment and anything else which may have come into contact with boxwood plants should be properly sanitized before entering a nursery. This is especially relevant for field-grown boxwood nurseries who sell plants to other nurseries on a piecemeal basis.
• Notify NCDA&CS field representative when buy-ins are received. Receipt date, source, number and type of buy-ins should be recorded in a format that can be examined upon request.
• Isolate buy-ins from other regulated articles in the nursery (including landscape plants) by a minimum of thirty (30) feet for a minimum of thirty (30) days. This time may be extended at the discretion of the NCDA&CS field representative if daily temperatures are not conducive for disease expression. Buy-ins may not be treated with fungicides during this holding period.
• Inspect buy-ins for symptoms weekly during the holding period and record inspection results on a form that can be examined upon request.
• Keep records of all out-going shipments of boxwood blight host plants (Buxus, Pachysandra, Sarcococca).
• Train nursery personnel to recognize and scout for boxwood blight symptoms. Contact a
  NCDA&CS field representative if symptoms are detected at any time.
• Become familiar with best management practices (BMPs) for boxwood blight and incorporate BMPs into nursery practices when possible.
   

To participate in the boxwood blight compliance program please contact:

HT Tseng, NCDA&CS Plant Pathologist, (919) 707-3754 or HT.Tseng@ncagr.gov.

The best defense against boxwood blight is the use of good sanitation practices. Researchers at the Connecticut Agricultural Experiment Station have compiled a table useful for selecting and applying disinfectants. It is important to note that the disinfectants referenced at the link are effective for cleaning tools, equipment, and shoes, but these are not effective at sterilizing organic surfaces, such as soil, leaf litter, or plants themselves.

Information concerning preventive fungicide treatments, resistant varieties and more is available from NCSU Plant Pathology.

If you believe you have boxwood blight in your nursery or landscape please contact the NCDA&CS Plant Pest Specialist in your area, which can be determined from the work area map, or contact HT Tseng, NCDA&CS Plant Pathologist at (919) 707-3754, or HT.Tseng@ncagr.gov.