The proposal to add a viability confirmation status to index field classification, update the detection threshold for designating a field as potato wart positive, and introduce a field of concern classification have all been made available for consultation by the Canadian Food Inspection Agency (CFIA) for sixty days.

Stakeholder comments can be submitted to the CFIA by October 7, 2024, via email using the subject line “Potato wart consultation”: cfia.potatosection-sectiondespommesdeterre.acia@inspection.gc.ca

The National Potato Wart Response Plan, which will replace Canada’s Potato Wart Domestic Long-Term Management Plan, is being updated as part of this process.

For the potato wart to be detected in a field, the CFIA suggests that the current detection threshold be updated. Rather than requiring two or more Synchytrium endobioticum spores in a single soil sample from the field, the new threshold would be two or more spores from the sampled field (not limited to a single soil sample or sample event) confirmed by two analytical methods, molecular and morphological.

Furthermore, if symptomatic tubers have also been verified in the field, the CFIA is recommending the creation of two classifications for potato wart index fields, also known as potato wart detected fields.

Index – viability confirmed: will be used for fields that meet the “detected” threshold (two or more spores in the field) and where symptomatic tubers have been observed either directly from the field or in laboratory bioassays for fields in the associated potato wart “cluster”.

Index – viability not confirmed: will be used for fields that meet the “detected” threshold (two or more spores in the field) but where there are no confirmed symptomatic tubers or evidence of spore increase for fields in the associated potato wart “cluster”.

Index – viability not confirmed fields will undergo a further diagnostic process of soil to determine spore viability via laboratory bioassay. If viability cannot be demonstrated, the field can be reclassified as a primary contact field and released according to the phytosanitary protocol in the National Potato Wart Response Plan, if there is no known association with a potato wart cluster where symptomatic tubers were identified.

Additionally, the CFIA wants to classify areas of concern. These are suggested areas where morphological and molecular analysis identifies and validates a single S. endobioticum spore. Potatoes from these fields will not be eligible for export certification based on the Potato Wart Order (Canada) and the U.S. Federal Order 2022 while under the extra investigation process. These fields will be limited until further intensive soil sampling is completed.x4a

Background on CFIA’s previous consultation on three main focal areas for mitigation measures, as part of drafting the National Potato Wart Response Plan, can be found in the following Gain Report: Canada Consults on National Potato Wart Response Plan_Ottawa_Canada_CA2024-0020.

To date, two provinces in Canada have reported potato wart: Newfoundland and Prince Edward Island (PEI). Newfoundland is considered endemic for potato wart, where it was first reported in 1909, with strict biosecurity measures in effect, including a prohibition on moving potatoes out of the province. Potato wart was first detected on PEI in 2000. A U.S. Federal Order was implemented in 2015 following additional detections in PEI which specified import conditions for PEI potatoes to prevent the introduction of potato wart to the United States. The U.S. Federal Order was amended in April 2022, following 2021 detections of potato wart in two PEI potato fields, prohibiting the importation of PEI-grown seed potatoes into the United States while allowing imports of PEI potatoes for consumption that meet specified conditions.

Following the 2021 detections, CFIA initiated an investigation into potato wart on PEI. The results of soil sampling from that investigation, along with previous potato wart detections, have led to a cumulative total of 37 PEI fields testing positive for potato wart since 2000; and the investigation which took place from October 2021 to July 2023 resulted in 4 detections from 48,789 samples. Fields with confirmed potato wart are classed as restricted fields and undergo a period of evaluation for several years before restrictions can be released.