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A new highly virulent race of Puccinia graminis, Ug99, which was discovered in East Africa in 1999, has spread to other parts of Africa and to wheat growing regions in the Middle East and Central Asia.  According to the Food and Agriculture Organization (FAO), the unique thing about Ug99 is the broad spectrum of virulence it exhibits as not only has it defeated the Sr31 resistance gene, a widely used gene that has been effective in wheat for over 30 years, but also most of the resistance genes of wheat origin and other key genes like Sr38 from related species.  Since its discovery more than a decade ago, Ug99 has held the agricultural world in suspense as governments and scientists rush to protect wheat crops.

To protect Michigan’s wheat industry from the threat posed by Ug99 and new strains of other rust fungi, Michigan Department of Agriculture and Rural Development (MDARD) in collaboration with the U.S. Department of Agriculture, conducted a barberry and black stem rust survey in the state in 2010-2011.  The objectives of the survey were: 1) to verify that all barberry cultivars offered for sale in the state were those of Japanese barberry (Berberis thunbergii), a species known to be immune to black stem rust;  2) that Common barberry had not reestablished in the state; and 3) to determine the status of black stem rust in Michigan wheat fields.

Methods and Procedures
In 2010, a total of 150 barberry plants representing 17 cultivars from propagating nurseries were collected by MDARD and shipped to Dr. Mark Brand’s laboratory at the University of Connecticut for DNA analysis using seven Amplified Fragment Length Polymorphism (AFLP) markers.  An additional 161 plant samples were collected from retail outlets and maintained in a hoop house for DNA extraction at MDARD’s Plant Pathology Laboratory in East Lansing.  Polymerase Chain Reaction (PCR) quality DNA was extracted from the plant samples and sent to Dr. Brand’s laboratory for analysis and cultivar determination.  

In February 2011, field surveys for Common barberry and black stem rust were conducted in accordance with standard wheat scouting and inspection procedures.  

The seven-marker AFLP procedure used at Dr. Brand’s laboratory successfully confirmed all 150 barberry plant samples from the propagating nurseries as true-to-name for their respective cultivars of B. thunbergii.  AFLP analysis of the 161 retail outlet samples confirmed 151 of the samples as true-to-name and 10 as mixtures of B. thunbergii cultivars.  
Black stem rust of wheat was not detected in surveyed fields; however, wheat leaf rust and stripe rust, common pests found in all wheat growing regions of the world, were detected on samples from two fields.  Field surveys did not detect wild populations of Common barberry.  The survey results indicate that Common barberry has not reestablished in the surveyed wheat production areas of the state.

Stem Rust Ug99 – an Agricultural Bully. Scientific American: June 20, 2011.

The Emergence of Ug99 Races, a threat to World Wheat Production. Annual Review of Phytopathology: Sept. 2011- Vol. 49, pp. 465-481.

Molecular Identification of Japanese Barberry (Berberis thunbergii) Cultivars Using Amplified Fragment Length Polymorphism. HortScience: June 2007, vol. 42, no. 3, pp. 478-482.

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.

-    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.

-    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.

-    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.

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
–    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.

MNLA Member Firms Committed to Preventing Boxwood Blight

Boxwood Blight Found in Michigan (Dec. 2018, PDF)

Boxwood Blight Best Management Practices (PDF)

Reclaiming Boxwood From Boxwood Blight (PDF)

Boxwood Blight Resource Sheet (PDF)

Prevention and Management of Boxwood Blight (PDF)

Best Management Practices for Boxwood Blight: Industry Recommended Best Management Practices for the Prevention and Eradication of Boxwood Blight within a Nursery (PDF)

Boxwood Blight Disease Identified in North America (PDF)

Shoot blight of boxwood-Calonectria pseudonaviculata
A diagnostic fact sheet from ARS-USDA

Boxwood Blight - a New Disease for Connecticut and the U.S.
An introduction to the disease from The Connecticut Agricultural Experiment Station (www.ct.gov/caes)

A New Pest to the U.S. Ornamental Industry: The “Box Blight” Pathogen (PDF)
North Carolina State University reviews the biology, spread and diagnosis of Boxwood Blight.

The Box Blight Pathogen (PDF)
Information from the Rhode Island Department of Environmental Management

The Michigan Certified Nurseryman specialty has been developed for Green Industry professionals who grow annuals, perennials, shrubs and/or trees in a nursery or greenhouse setting. Topics that are covered by this specialty include:

•    Nursery Operations
•    Propagation
•    Soil Properties and Soil Fertility
•    Container Substrates and Nutrition
•    Water Quality and Management
•    Implementing a Nursery Scouting Program
•    Insect Pests of Nursery Plants
•    Weed Management
•    Plant Disease Management
•    Industry Laws and Regulations
•    American Standard For Nursery Stock

Study Manuals to assist you in preparing for the CGIP Exam are available for purchase.

How to Become a Michigan Certified Nurseryman

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