BMPs to Prevent the Introduction or Establishment of Phytophthora ramorum in Nurseries
In this section, we discuss:
- The best ways to prevent your nursery from becoming infested with Phytophthora ramorum
- How to prevent the pathogen from establishing if it is accidentally brought into the nursery
- How to minimize losses if Phytophthora ramorum is found in your nursery
The following recommended Best Management Practices are based on the national guidelines for Best Management Practices developed jointly by the nursery industry, state departments of agriculture, and scientists. Most of these BMPs are voluntary, but some of them (indicated in bold text on following pages) are required by state or federal regulatory agencies. (See the section on regulations for a complete description of federal and state requirements pertaining to Phytophthora ramorum.
Pest Prevention and Management—Exclude the Pathogen
The best way to avoid contamination by Phytophthora ramorum is to prevent it from getting into your nursery in the first place. The following steps are key.
- Propagate nursery stock from plants on-site, or make sure that the source nursery is free from Phytophthora ramorum. Phytophthora ramorum-free certification programs exist in California, Oregon, and Washington.
- In Oregon: Notify the Oregon Department of Agriculture (ODA) if your nursery will be receiving tree and shrub nursery stock from outside Oregon. You must notify ODA within 2 business days after receiving stock, although prenotification is highly encouraged. Notification can be via mail, fax, or e-mail to: Nursery Program Supervisor, Plant Division, Oregon Department of Agriculture, 635 Capitol St. NE, Salem, OR 97301; fax 503-986-4564; e-mail to email@example.com
- A similar notification requirement applies in Washington state.
- Receiving nurseries of tree and shrub nursery stock imported into Washington State from any out-of-state source are required to notify the Washington state department of agriculture (WSDA). Notification methods may include U.S. mail, fax, delivery service or e-mail to: Nursery Inspection Program Supervisor, Plant Protection Division, Washington State Department of Agriculture, 1111 Washington St. S.E., P.O. Box 42560, Olympia, WA 98504-2560; fax 360-902-2094; e-mail: firstname.lastname@example.org
- Truckloads of incoming nursery stock should be inspected at the nursery by a well-trained individual right at the loading dock. Inspect all plants (buy-ins, transfers, and returns), regardless of origin, for symptoms of Phytophthora ramorum.
- Off-load regulated hosts and associated plants to an area that can be cleaned of leafy debris. Collect plant debris from the receiving area and the delivery truck, then dispose of it properly, either by incinerating, double bagging, and deep burial, or by steam sterilization. Do not compost it. Infected plant litter is a potential source of Phytophthora and other pathogens.
If possible, do not accept the return of plants sold to other nurseries. Returned stock may have been exposed to Phytophthora ramorum. If you must accept returns, keep them separate from your other nursery stock and watch them for symptoms of disease. Contact regulatory officials if symptoms appear.
Avoid mixing incoming plants with existing stock. Place incoming stock in a separate area away from existing stock for several weeks, if possible.
- Be particularly alert for disease symptoms on Camellia and Rhododendron. These are considered at high risk for Phytophthora ramorum infection.
- When bringing in new high-risk plants (Camellia and Rhododendron), do not use Phytophthora-specific fungicides on 10% or 100 of the plants, whichever is fewer, for 2 months. Then monitor the untreated plants regularly for disease symptoms. This will help determine whether the plants were infected, but were not showing symptoms due to fungicides the seller may have been using.
- Make sure that trucks used to ship high-risk plants are cleaned between shipments to remove plant debris and mud. Also wash the truck undercarriage and tires.
Pest Prevention and Management—Manage Water
Review Module 2 for a detailed discussion of water management. Here are key points:
- When irrigating, avoid prolonged leaf wetness. Avoid overhead irrigation of high-risk plants. Properly time irrigation to reduce conditions favorable for disease development.
- If you use irrigation water from any source other than a well or municipal water supply, test the water annually to confirm that it is free from the pathogen. Nurseries that use water from ponds, lakes, and streams, or that blend both well and surface water sources, should treat the water before using it for irrigation.
- Divert runoff from adjacent properties with Phytophthora ramorum host plants to prevent contaminating your nursery.
- Avoid or minimize standing water in the nursery wherever possible, but especially in beds of Rhododendron and Camellia.
Pest Prevention and Management—Adjust the Nursery Layout
To reduce the spread of spores from high-risk plants to other plants:
- Create a 2-meter (6.5 feet) break between high-risk plants and all other crops, or
- Develop a preventive spray program when plants have leaves, or
- Use raised benches or raised beds, if feasible, for both indoor and outdoor production sites.
- Review your field layout plan. Determine how you can minimize the impact of the USDA Confirmed Nursery Protocol (see Regulatory section) if Phytophthora ramorum is found. One way is to separate long sections of host and associated-host plants (HAP) by inserting plant-free areas that are 2 meters (6.5 feet) wide (see below).
- Maintain a separate dump pile for host plant discards. Do not include them in the recycling pile for future reuse. Isolate the dump pile far away from potting media components, mixing areas, and growing beds.
Schematic of Destruction (D) and Quarantine (Q) Radii.
D and Q radii for positive plants, positive standing water, or positive soil or other articles as appropriate. From Appendix 2, Confirmed Nursery Protocol version 8.2, Aug. 6, 2014.
|Once D and Q radii are flagged, then:
|Destroy all plants, containers, and leaf debris
|Hold HAP from sale for 90 days; if there is non-HAP mixed in it can be taken out and moved. For water or soil positive, the Q radii is 1 meter.
|Destroy all plants; non-HAP nursery stock could still move the pathogen
|Quarantine radiiin Non-HAP Block
|Release non-HAP for sale if found symptomless during the delimiting survey
|The rest of the HAP block
|Release all plants for sale only found symptomless during the delimiting survey
|The rest of the HAP block
|Release all plant material for sale if found symptomless during the delimiting survey
Pest Prevention and Management—Keep the Nursery Clean
- Remove and dispose of leaf debris.
- After every crop rotation, disinfect propagation mist beds, sorting area, cutting benches, machines, and tools to minimize the spread or introduction of pathogens.
- Use new pots or sanitize used pots for production of high-risk plants.
- Take cuttings from apparently healthy stock plants, and soak cuttings in an approved disinfectant solution before sticking.
- Put an effective barrier such as a 6-inch layer of gravel between the native soil and the container to prevent splashes from potentially infested ground.
- Place containers on benches 12 to 18 inches off the ground.
- Ensure that the potting media are from an area known to be free from Phytophthora ramorum. Prevent contamination from potentially infested compost, bark, or other organic components of the substrate. Store media on a cement pad where they cannot become contaminated by soil, runoff water, or vehicles.
- Adequately control weeds on the nursery site. Weeds can harbor the pathogen.
- If you visit areas known to be infested with Phytophthora ramorum, wash shoes, tools, and vehicles that may have contacted contaminated soils before traveling to disease-free areas.
- Remove known hosts of Phytophthora ramorum planted on the nursery grounds, or monitor regularly for Phytophthora ramorum.
- Direct runoff from all cull piles away from soil components, soil mixing areas, and growing beds to prevent contamination. Ensure the cull pile is clearly separated from soil-mix components.
- Clean vehicles and boots of mud and plant debris regularly (at least several times per day).
Pest Prevention and Management—Inspect Plants
- Regularly inspect all HAP in the nursery and in the surrounding landscape for symptoms of Phytophthora ramorum.
- Inspect Camellia, Rhododendron, and other highly susceptible plants monthly throughout the year.
Train Nursery Personnel
- Each nursery should designate certain people to manage Phytophthora ramorum. The designated managers should attend one or more Phytophthora ramorum APHIS-approved training sessions annually. Training is available through the USDA, U.S. Forest Service, California Oak Mortality Task Force, state departments of agriculture, county agricultural commissioner offices, and selected universities, such as this course from OSU.
- OSU Extension offers training classes in English and Spanish several times a year. Check for availability and participate.
- Train field, propagation, and shipping staff to recognize and report all pest and disease problems.
- Consult with your state department of agriculture, county agriculture department, and/or knowledgeable university personnel to identify the specific BMPs from this list that are appropriate for your nursery. Educate your employees and managers about your nursery's BMPs for Phytophthora ramorum.
- Keep records of all incoming and outgoing plants to enable tracing them if Phytophthora ramorum is found. For at least 2 years, you should keep accurate shipping documentation identifying HAP product, amount, date, and origin or receiver.
- Nurseries should maintain records for 24 months of all incoming and outgoing shipments of host and associated host plants. Records of these shipments should include species and variety of cultivar, origin of incoming shipments, numbers of plants, dates, and the destination of outgoing shipments.
- Consider ways that you could rapidly identify potentially infected plants if Phytophthora ramorum is found in a supplier’s stock, or in stock you have shipped, or both.
Each nursery should compile a manual of Best Management Practices. This should include a checklist of implemented BMPs appropriate for your site based on:
- The nursery's specific production system
- Its physical location
- Nursery type
- Regional climatic conditions
- Plants grown
It should also include:
- Evidence, such as written records initialled and dated by nursery personnel, that the BMPs are being carried out
- Employee training records
- An internal review procedure