Potato blights develop fungicide resistance

Leaf samples taken last summer by provincial potato specialists and ag chem firm Bayer CropScience throughout Canada show "widespread"presence of fungi that have mutated to resist the fungicides used most often to control them.

The sampling program found 113 isolates of Alternaria solani, the cause of early blight in potatoes. Of those, Bayer said in a release last week, over 80 per cent carried the F129L mutation that causes "reduced sensitivity to strobilurins."

That's not to say strobilurins won't work at all, but that they "don't work as well as they have in the past for controlling early blight,"Bayer said.

Early blight leaf tissue samples were collected during the summer of 2008 in Alberta, Manitoba, Ontario and Prince Edward Island by potato specialists and Bayer sales reps, the company said.

"Initial results confirm that mutant strains are widespread in Alberta, Manitoba and Ontario, which is not surprising given the widespread distribution of mutant strains of the early blight fungus in the United States,"said Rick Peters, a research scientist with Agriculture and Agri-Food Canada at Charlottetown, in Bayer's release.

"To date, P.E.I. is the only area that we've surveyed where all samples were still sensitive to strobilurins, likely due to the less frequent use of strobilurins in this province."