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Boxwood Blight Cleanliness Program and Compliance Agreement for Production Nurseries

Photos from top:  Lesions on Buxus; Lesions on leaf surface of Pachysandra; and Lesions on underside of leaf surface. Photos courtesy of Connecticut Agricultural Experiment Station.

In The Michigan Landscape, The Michigan Department of Agriculture and Rural Development (MDARD) recently provided information on Boxwood Blight, a disease of boxwood (Buxus spp.), sweetbox (Sarcococca spp.), and Japanese pachysandra (Pachysandra terminalis) caused by the fungus Cylindrocladium pseudonaviculatum (syn. C. buxicola).  In order to minimize the effect of this serious disease on the nursery industry, the American Nursery and Landscape Association (ANLA) and the National Plant Board developed the Boxwood Blight Cleanliness Program.  The program uses a systematic approach to clean plant sourcing, early detection, and prevention of spread.  MDARD is adopting the program in a slightly amended form and will offer production nurseries an opportunity to have their host plant materials certified under the terms of a Boxwood Blight Cleanliness Program Compliance Agreement.  Key requirements for growers wanting to participate in the program follow.

Pathogen Exclusion
-    Utilize suppliers or nurseries that have been officially inspected by MDARD and certified free of this disease or that hold a Boxwood Blight Cleanliness Program Compliance Agreement;
-    inspect incoming host plants (including cuttings) at the time of delivery and contact MDARD if signs or symptoms of the disease are suspected;
-    isolate by distance or barrier any newly received host plants from existing plants or plants from another source, for at least 30 days;
-    avoid applying fungicides that could prevent detection of the disease;
-    locate plants on a surface that can be cleaned and positioned to prevent water runoff into potting media and host production areas; and
-    use sanitation measures for vehicles and for host plants being returned to the nursery.  

Water Management
-    Avoid overhead watering;
-    watering in a manner that ensures that leaves are dry before nightfall;
-    monitor for host plant debris in water run-off;
-    minimize water run-off between production sites; and
-    minimize standing water in host plant blocks.

Sanitation
-    Inspect host plant production areas regularly for host plant debris;
-    remove host plant debris by regular cleaning, and do not add it to compost;
-    sanitize tools and equipment between blocks with an effective disinfectant;
-    sanitize the production area at the end of each production cycle after first removing all crop debris;
-    use new or sanitized pots and flats for production; and
-    use new potting media, or sterilize used potting media prior to reuse.

Inspection
-    Employ trained personnel to inspect host plants in isolation areas on a weekly basis;
-    report plants with signs or symptoms of the disease to MDARD; and
-    withhold suspect plants from sale or distribution until MDARD has inspected and certified them.

Training of Personnel
-    Recognize the basic signs and symptoms of the disease;
-    use proper sanitation practices to meet the intent of the Compliance Agreement, including  worker safety; and
-    use approved training materials made available by ANLA, National Plant Board, and MDARD websites.

Recordkeeping
-    Maintain wholesale receiving and shipping documents, including certificates of inspection, for 36 months after the date or receipt or sale, whichever is later (this requirement  of Michigan’s Act 189 supersedes the ANLA guideline of 12 months); and
-    maintain records showing the quantity and source of incoming plants, location of isolation areas, dates of inspection, fungicide applications (for non-isolated materials), and personnel training.

As with nursery stock and other plant materials, MDARD may conduct inspections of boxwood blight host plants, production sites, records, etc. in order to determine if the disease is present and to verify that a participating nursery is meeting the terms of the Compliance Agreement.

Why participate?  Boxwood blight has been identified in several states.  It’s important to stop the spread of the disease, and growers wanting greater market access will have to ensure that host plants are free from the disease.  Participating in the Boxwood Blight Cleanliness Program will allow growers to show that they handle and produce host plants using procedures developed by ANLA and the National Plant Board aimed at minimizing risk from this disease.  It also allows growers to work with MDARD to assure that host plants coming out of Michigan are of high quality and to take a greater stake in the nursery stock they produce.

How can growers participate?  Ask for more information from your MDARD inspector or from Mike Bryan, MDARD’s Nursery Program Specialist at 517-241-2977.