Late blight has been identified in eight parishes across the Canadian province New Brunswick, threatening the crops of potato growers.
Scientists are urging growers who have the fungus in their fields to treat it quickly and aggressively.
"If the area is a larger area, what we recommend is that the grower top-kill that area. So they use a chemical that kills the plant," said Dr. Khalil Al-Mughrabi a potato pathologist with the Potato Development Centre in Wicklow.
This summer's humid weather is the perfect condition for late blight, which can wipe out entire crops, said Al-Mughrabi.
It also spreads quickly, he said, noting the first case in the province was only reported at the end of July.