Potato Wart Domestic Long Term Management Plan

On this page

• Background
• Summary of the management plan
  • Category A: index fields
  • Category B: adjacent fields
    • Adjacent fields used for potato production
    • Adjacent fields not used for potato production
  • Category C: primary contact fields
    • Primary contact fields used for potato production
    • Primary contact fields not used for potato production
  • Category D: other contact fields
  • Category E: new fields entering potato production
• Definitions
  • Common definition of field for the purpose of the Potato Wart Domestic Long Term Management Plan
• Soil sampling and testing
• Visual inspection

Background

The Potato Wart Domestic Long Term Management Plan outlines the restrictions and surveillance activities for potato wart in Prince Edward Island (PEI) to reduce the risk of spread of potato wart and protect potatoes, potato production, trade and the economy.

Potato wart is a soil-borne fungus (Synchytrium endobioticum) that can remain dormant in a field for over 40 years. Although potato wart poses no threat to human health, animal health or food safety, it reduces yield and makes potatoes unmarketable. For more information on potato wart, refer to Synchytrium endobioticum (Potato wart or Potato Canker) fact sheet.

Summary of the management plan

Category A: index fields

These are fields where potato wart has been detected.

Under the current management plan, when potato wart is detected, the initial restrictions and surveillance activities include:

• containment and safe disposal of soil and crops
• if there is a potato crop in the field, only processing end use within the province is permitted with risk mitigation measures in place
• restriction of soil movement
• cleaning and disinfecting of equipment
• for future crops, only non-host crops can be planted, no potatoes permitted for at least 5 years
• planting of any material intended for propagation is prohibited
• 4 m × 4 m grid soil sampling
  • soil microscopy for potato wart
• Post-harvest field inspection and tuber inspection for potato wart

Five years after a detection, and when spore counts in the soil are < 5 spores/g of soil and the bioassay is negative, the production of resistant potato varieties may be permitted, with full cleaning and disinfection and processing end use within the province with risk mitigation measures in place. Post-harvest field inspection and tuber inspection for potato wart are required.

Five years after the initial detection, and at every five years, surveillance activities include:

• 4 m × 4 m grid soil sampling (five years after the initial detection, and at every five years)
  • soil microscopy for potato wart
  • bioassay tests for potato wart

When spore counts in the soil are < 5 spores/g of soil and the bioassay is negative, the production of resistant potato varieties may be permitted, with full cleaning and disinfection and processing end use within the province with risk mitigation measures in place.

Fifteen years after the planting of resistant varieties, when regular soil samples indicate < 5 spores/g of soil in each sample and potato wart is not detected in all bioassays:

• production of potato wart-susceptible potato varieties may be permitted
• cleaning and disinfection and soil movement restrictions may be lifted, except that tare soil must be returned to the index field
• processing end use within the province remains a requirement
• post-harvest field inspection and tuber inspection for potato wart for at least 3 crops of a potato wart-susceptible potato variety in conducive conditions

For a field to be released from all restrictions, negative results for three further crops of potato wart-susceptible potato varieties grown under conducive conditions are required.

Category B: adjacent fields

Adjacent fields used for potato production

These are fields used for potato production next to an index field that are not separated by a physical barrier of more than 15 m width. For all adjacent fields used for potato production, the initial restrictions and surveillance activities include:

• containment and safe disposal of soil and crops
• only processing end use within the province is permitted with risk mitigation measures in place
• restriction of soil movement
• cleaning and disinfecting of equipment
• only non-host crops can be planted
• planting of any material intended for propagation is prohibited
• 8 m × 8 m grid soil sampling
  • soil microscopy for potato wart
• post-harvest field inspection and tuber inspection for potato wart

Once the results of soil testing and post-harvest field inspection for potato wart-susceptible potato varieties indicate that potato wart is not detected:

• cleaning and disinfection and soil movement restrictions may be lifted, except that tare soil must continue to be controlled.
• processing and table stock end-use of potatoes is permitted, but they must receive a phytosanitary inspection

Once there is acceptable surveillance on three additional crops of a potato wart-susceptible potato variety, end use will be limited to processing and table stock only. Seed production is not permitted.

Once all soil restrictions, treatment and packaging requirements are lifted and surveillance activities are acceptable for two additional crops of a potato wart-susceptible potato variety in conducive conditions, the field may have all restrictions lifted. Seed production is only permitted after all restrictions are lifted for the index field.

Adjacent fields not used for potato production

These are fields not used for potato production next to an index field that are not separated by a physical barrier of more than 15 m width.

Risk is reduced when the field has not been used for potato production in 20 years or more and the field is not intended for future use in potato production.

For all adjacent fields not used for potato production, the initial restrictions and surveillance activities include:

• containment and safe disposal of soil
• restriction of soil movement
• cleaning and disinfecting of equipment
• only non-host crops can be planted
• 8 m × 8 m grid soil sampling
  • soil microscopy for potato wart

On the 15 m portion of the field immediately adjacent to the index field:

• 4 m × 4 m grid soil sampling
  • soil microscopy for potato wart
  • bioassay test for potato wart

Once the results of surveillance activities above indicate that potato wart is not detected, cleaning and disinfection and soil movement restrictions may be lifted.

Category C: primary contact fields

Primary contact fields used for potato production

These are fields used for potato production that may have had soil or host plants transferred to them from an index field, or had common equipment moved to them directly after use in an index field. For all primary contact fields used for potato production, the initial restrictions and surveillance activities include:

• containment and safe disposal of soil and crops
• restriction of soil movement
• cleaning and disinfecting of equipment
• only processing end use within the province is permitted with risk mitigation measures in place
• 8 m × 8 m grid soil sampling
  • soil microscopy for potato wart
• post-harvest field inspection and tuber inspection for potato wart

Once the soil test and one post-harvest field inspection for a potato wart-susceptible potato variety indicate that potato wart is not detected, cleaning and disinfection restrictions may be lifted. Potato production will be limited to processing and/or table stock with a phytosanitary inspection on table stock.

Once surveillance activities are acceptable for three additional crops of a potato wart-susceptible potato variety in conducive conditions, all remaining restrictions may be lifted.

Once all restrictions are lifted, mandatory surveillance of two further crops of potato wart-susceptible potato varieties grown under conducive conditions is required.

Primary contact fields not used for potato production

These are fields not used for potato production that may have had soil or host plants transferred to them from an index field, or had common equipment moved to them directly after use in an index field.

For all primary contact fields not used for potato production for >20 years, the initial restrictions and surveillance activities include:

• restriction of soil movement
• cleaning and disinfecting of equipment
• only non-host crops can be planted
• 4 m × 4 m grid soil sampling
  • soil microscopy for potato wart
  • bioassay tests for potato wart

Once the results of surveillance activities above are negative, soil movement restrictions may be lifted.

Category D: other contact fields

These are fields where common equipment has been shared with an index field, after use in a primary contact field.

For other contact fields, the following is required:

• 8 m × 8 m grid soil sampling
  • soil microscopy for potato wart
• any fields used for potato production are subject to post-harvest field inspection and tuber inspection for potato wart

Once surveillance activities for the first crop of a potato wart-susceptible potato variety are acceptable, all restrictions on potato end use domestically are lifted, table stock and processing potatoes are permitted.

Mandatory surveillance of four further crops of a potato wart-susceptible variety in conducive conditions is required.

Category E: new fields entering seed potato production

These are fields not previously used for potato production. These fields are likely to have minimal risk for potato wart.

If there is any degree of risk of potato wart infection, a post-harvest field inspection is required.

If surveillance activities are acceptable, the field will be considered potato wart free.

Definitions

Bioassay involves growing a potato variety that is susceptible to potato wart (usually in a greenhouse) in soil collected from a field to see if symptoms develop on the tubers or plants.

Conducive conditions/conducive environmental conditions where potato wart grows best are cool, wet growing seasons.

Fields under restrictions are any parcels of land under restrictions to reduce the risk of spread of potato wart, and may be Category A, B, C or D. Category E is land that is entering seed potato production for the first time and requires post-harvest field inspection to confirm the absence of potato wart.

Potato wart host crops are crops in the family Solanaceae that are susceptible to potato wart.

Resistant varieties are varieties of potato that are resistant to potato wart.

Soil sampling grids determine the spacing between sub-samples.

Tare soil is the soil found on potatoes after harvesting. It falls off during handling and storage.

Types of potatoes

Table stock are potatoes to be prepared fresh, cooked and eaten.

Processing end use means potatoes that are turned into other products (for example, French fries, potato starch), and not consumed fresh.

Seed potatoes are eligible to be planted to grow other potatoes under the Canadian National Seed Potato Certification Program.

Common definition of field for the purpose of the Potato Wart Domestic Long Term Management Plan

For the purpose of the Potato Wart Domestic Long Term Management Plan, a field means:

• a distinct plot of land distinguished from neighbouring plots of land by physical boundaries

If potato wart is confirmed within a field, the entire field, as defined by its physical boundaries, will become a restricted area and be under regulatory control. This definition is applied to all restricted fields (Category A, B, C or D) under the Potato Wart Domestic Long Term Management Plan and the regulation of other pests including potato cyst nematodes (PCN) and potato rot nematode (PRN).

A physical boundary means:

• tree line
• fence line
• permanent waterway
• ditch
• road or permanent lane
• berm
• permanent irrigation track
• transition to a non-agricultural area (fallow, lawn, wetland)
• real property boundary

A description of a real property boundary is when specific conditions are met (case by case basis) including:

• there is no freedom from soil requirement and no evidence of cultivation beyond the property line
• the producer(s) should contact us in writing and describe how the boundary will be maintained (physical markers or GPS)

It is recommended to add a physical boundary where possible.

In general, a portion of land that has never been in agricultural production should not be part of the restricted field. For example forest, wetlands or a residential property.

Scenarios for changing the boundaries of a restricted field

• when a restricted field is cultivated beyond its current boundaries, without biosecurity measures in place, the restricted area must be expanded
• when there is a new physical boundary established or a significant change to land use, separation of a previously established restricted field into two or more new fields may be required. In these situations, the field status will remain unchanged and would apply to the sub-divided portions of the original field

Landowners or land users should notify the Canadian Food Inspection Agency (CFIA) of the field boundary change(s) for a restricted field as soon as possible.

Surveillance activities of restricted fields

For surveillance activities, if a restricted field is cultivated in strips (for example it is divided into multiple sections for environmental or other reasons), and those strips are not static (the same year after year), the field may need to remain under regulatory control if the landowner or land user is not able to confirm that the entire area has been surveyed the minimum required number of times under the Potato Wart Domestic Long Term Management Plan.

When the strip of field remains static and partial surveillance can be documented following the planting of a susceptible potato crop, the field may be eligible for release from regulatory control. The required number of complete surveillance activities must be met.

Soil sampling and testing

Soil samples are collected as part of the potato wart management plan:

• as part of investigations related to findings of potato wart
• from some regulated fields every five years

Soil samples may be used for microscopy testing and for bioassays. The number of samples is higher in years where potato wart investigations are triggered or additional monitoring is required. During an investigation, the number of samples collected can vary greatly depending on the size of the field and the number of fields involved.

To collect a sub-sample, a soil probe is inserted to the field and removes a sub-sample to a depth of 20 cm. When the sub-samples combine for a total of approximately 2.27 kg or 2000 cc of soil, they are placed in a sample bag. A sample is typically made of about 35 sub-samples. For example, a 1 ha field measuring 100 m × 100 m, a 4 m by 4 m sampling grid would result in 625 sub-samples, 18 samples and approximately 41 kg of soil submitted for testing.

To minimize impact on growing crops, samples are collected during the spring or fall. Most samples are collected in the fall after crops have been harvested, before the ground freezes.

Visual inspection

Post-harvest field inspection takes place during or shortly after harvest. An inspector walks across the whole field in a pattern to visually inspect potato tubers and plant material left behind.

Tuber inspection is a visual inspection of potatoes as they enter or leave storage, or at any time an inspector wishes to view tubers.