Researchers working to 'get the upper hand' on potato wart, but warn solutions will take time

A field just outside St. John's could one day hold the key to treating or eliminating a fungus that dealt a huge blow to P.E.I.'s iconic potato industry four years ago, and continues to have ripple effects today.

A section of field at Agriculture and Agri-Food Canada's Avondale Research Farm in Newfoundland was intentionally infected with potato wart around 50 years ago. 

The only known facility dedicated to potato wart research in the world, Avondale allows scientists to study the life cycle of the soil-borne fungus, Synchytrium endobioticum, and possible methods of controlling it.  

"Once this disease is present in the soil, the spores… of that fungus that cause the disease can live in the soil for 10, 20, 50 years," said Linda Jewell, a research scientist who studies plant diseases at the Avondale farm. 

"There's no way that we know of to get rid of them, other than simply time."

The discovery of potato wart in samples from six Prince Edward Island fields back in 2021 led the Canadian Food Inspection Agency to seek a ministerial order banning all potato sales from this province to the U.S. market for four months. 

Over the course of the investigation, CFIA staff collected and analyzed nearly 50,000 soil samples from fields associated with detections of the fungus, which disfigures potatoes and sharply reduces crop yield but is not harmful to humans.

Though many truckloads went to food banks, hundreds of millions of pounds of Island potatoes had to be destroyed over the winter of 2022 because no buyers could be found. 

The export of fresh table potatoes eventually resumed, but a federal ministerial order restricting shipments of seed potatoes from P.E.I. remains in effect.

'Really difficult disease'

There are no known fungicides for potato wart and it can't be grown in a lab, making it difficult and time-consuming to study, said Jewell. 

But since the 2021 detections in P.E.I., the Avondale Research Farm has ramped up its efforts to understand how to control the spread of potato wart and treat fields that have it. 

"In general, we're looking for… various ways that we might be able to get the upper hand on this really difficult disease," Jewell said. 

That work includes growing a variety of potatoes to determine whether they're resistant to the fungus and studying its genetics for a "weak point" that would allow researchers to target the disease. 

They're also testing new and traditional fungicides in hopes of striking it lucky. 

The ultimate goal is to find something growers can use on their fields to prevent or treat potato wart, but Jewell said the solution is still a long way off. 

"We recognize that… best-case [scenario] would be several years down the line," she said. "Potato wart is a very unusual disease and it's fairly difficult to work with. It doesn't behave like many other fungi, and that makes it very difficult for us to do the types of studies in the lab." 

The last thing that growers need to worry about is another very difficult disease.— Linda Jewell, Avondale Research Farm

The 2021 potato crop in P.E.I. had been called the best in generations, following three poor growing years.

The detection of potato wart was devastating to farmers, with the province going so far as to set up a helpline for mental health support. 

Jewell hopes the work being done at Avondale will eventually ease that kind of burden for good. 

"It's already very difficult to be a farmer. Of course it's a lot of very hard work and a lot of economic stress, and the last thing that growers need to worry about is another very difficult disease," she said. 

"It would really be very rewarding to help contribute to something that… takes one more worry off of the list."