The Canadian Food Inspection Agency is confirming that potato wart fungus has been found in soil from two fields on a farm in Queens County, Prince Edward Island.
In an email to CBC News, CFIA said the potato wart was found on October 16, 2020, in soil that was being collected for routine export testing.
It said there are approximately 20 hectares, in the two fields combined, on the farm where the fungus was found.
The agency has not indicated where exactly the farm is located, other than specifying it was Queens County.
Following the detection, CFIA said it took immediate action to secure the farm and prevent potential spread.
Potato wart poses no risk to humans or food safety, but it can be a serious disease for the infected potatoes, which become disfigured, making them unmarketable.
It also prevents tuber production and can affect export markets.
CFIA said potato wart can remain dormant in a field for more than 20 years. It is spread through the movement of infested tubers, soil and farm equipment.
CFIA indicated it has sampled material from the fields affected to determine the possible sources of the fungus.
Testing of the source fields that supplied the seed potatoes for the positive fields in 2020 has also been completed, and they are negative for potato wart.
The agency said the testing of other samples continues, as does the investigation.
CFIA said no seed potatoes from the 2020 harvest have been shipped from this farm, and it has prohibited movement of seed potatoes or soil from this farm to other locations.
The CFIA has identified the fields where the potatoes produced in previous years were planted, and has conducted soil sampling there as well.
In a notice to producers in November, CFIA reported that "to address concerns raised by the United States, the export of seed potatoes originating from P.E.I. and destined to the United States has been suspended, as of Friday, November 20, 2020."
It noted that this suspension does not apply to tablestock potatoes or potatoes for processing.
CFIA said there have been no changes in inter-provincial movement of seed potatoes originating from P.E.I.
The National Potato Council represents U.S. potato growers and supply chain partners.
In response to the CFIA announcement, the council's CEO Kam Quarles released a statement about the situation on P.E.I.
"The National Potato Council supports CFIA's immediate action to stop all P.E.I. seed shipments into the United States and are working with our state potato organizations to inform U.S. growers who may be intending to source seed from P.E.I. for the upcoming year," the statement said.
"We have been advised that no seed from the identified areas has been shipped to the United States in four years. However, we are working closely with USDA to monitor recipients of seed in years-past out of an abundance of caution.
"We are in communication with APHIS regarding CFIA's ongoing survey work to comprehensively determine the level of threat within Canada and are also urging CFIA to prohibit all domestic seed shipments out of P.E.I. to prevent spread within Canada until they can confirm no other farms have been jeopardized."
CFIA said in its statement to CBC News that "the government of Canada will continue to work closely with the P.E.I. potato industry, the government of Prince Edward Island and the United States to resolve this trade disruption as quickly as possible."
In 2000, potato wart shut down trade between P.E.I. and the United States, when it was first found on the Island.
Since then, new protocols have been introduced for monitoring and controlling the spread of potato wart, and there have been no trade issues after subsequent discoveries of the fungus, including in 2012 and 2014.
The border closure in 2000 cost P.E.I. potato farmers $22 million in sales.
When reached for comment, the P.E.I. Potato Board referred all questions to CFIA.
A spokesperson for the P.E.I. Department of Agriculture and Land said that because there is an ongoing investigation by CFIA, it won't be commenting on this case.
According to the department, about 15 per cent of the potatoes grown on P.E.I. are used for seed, and about 80 per cent of that seed is used on Island farms.
It said seed exports account for two per cent of P.E.I.'s international potato exports.
The U.S. was the single biggest international buyer. In 2019, they bought $3.1 million worth of seed potatoes from P.E.I., out of $4.5 million exported.
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