Features Production Research
Eye on Potatoes: PCN highlights the need for effective pest regulations

The current battle to
control potato cyst nematode in Alberta and reopen borders to seed
potatoes from the province highlights the importance of improving
regulations to control pests before they become trade issues.

By Peter Mitham

Cameron Duff

CFIA official outlines harmonized testing protocols adopted by Canada and the U.S.

The current battle to control potato cyst nematode in Alberta and reopen borders to seed potatoes from the province highlights the importance of improving regulations to control pests before they become trade issues.

Speaking to British Columbia growers at the annual conference of the B.C. Potato and Vegetable Growers’ Association in Delta, B.C., last November, Cameron Duff of the Canadian Food Inspection Agency in Ottawa said Canada has identified more than 400 quarantine pests of plants. Of these, 80 are known to be in the country, putting producers at risk.

“When you prevent the entry of a pest, you have a relatively low cost to that introduction, you can eradicate that pest very quickly,” he said. “Once they’re established and widely enough distributed, then you have to manage them in accordance with international rules and guidelines, and also domestic procedures and also best-management practices, to enable producers to go on with their business in a productive way.”

Potato cyst nematode is among the top pests to have become a major issue for growers in the past two years. Spread by soil and the movement of infected tubers, PCN can reduce crop yields in potatoes and other host crops (including tomatoes and eggplants) by up to 80 per cent. It can survive for up to 30 years in the soil between host crops, making it difficult to eradicate.

PCN is even more problematic because it isn’t easily detected.

“You need several generations of replication of the cyst to get to detectable levels,” Duff said. “If you have alternate years in which you don’t have host crops, you also get a decline in the population.”

While crop damage starts to be seen at levels of approximately 10 million cysts an acre, detection is virtually impossible below 100,000 cysts an acre. Current import requirements for seed potatoes have a detection threshold of between 250,000 to 300,000 cysts an acre.

The gap means that cysts can be present several years and firmly established in a field for several years prior to detection, making it difficult for growers to eradicate. Since cyst numbers will fall without a host crop, rotating crops will help fight the problem but also make cyst populations difficult to detect.

Indeed, the disease was thought confined to limited areas of Canada and the U.S. prior to 2006. While Golden Nematode, one of two worms responsible for the disease, was identified on B.C.’s Saanich Peninsula in 1965, since 2006 the disease has also been detected at sites in Alberta, Idaho and Quebec (Pale Cyst Nematode is present only in Newfoundland, which also has Golden Nematode).

The latest detections prompted adoption of restrictions on the movement of seed potatoes on both sides of the border, in accordance with guidelines developed by Canada and the U.S. These included a testing regime for each field that was shipping potatoes between the two countries.

The highly integrated nature of the industry makes control a significant issue, and Duff noted that B.C. growers were not immune from the threat the pest poses. The significant potential for a wide distribution of seed from suspect farms in Alberta has prompted increased vigilance, he said.

The Canada-U.S. control guidelines provide for harmonized testing, a measure that promises to see 100 per cent of Canada’s seed potato acreage tested by 2010, as well as 10 per cent of commercial fields.

Testing will be phased in, beginning with all export potatoes in 2008; potatoes moving across state and provincial borders in 2009; and all remaining fields by 2010.

While there is a chance testing will allow the U.S. border to reopen to Alberta seed potatoes soon, Duff said a management program is required to ensure long-term stability for potato growers. One
element could be resistant varieties, which have effectively countered the disease in Europe. ❦