Late blight developments Canada

Manitoba Potato growers may consider switching to a shorter fungicide spray cycle as late blight continues to show up in fields throughout the potato growing regions of the province.

Vikram Bisht, plant pathologist with Manitoba Agriculture, Food and Rural Initiatives, says growers should avoid exceeding the maximum residue limits, which is quite possible if growers move from a five-day to four-day cycle.

"But it is probably OK in cases where the risk is extremely high,"says Bisht. "If there is disease in neighbouring fields, or if there's rain in the forecast for the coming days."

He points out close-to-ideal conditions over the last week have led to quick growth. Any plant material that has developed since the last application of fungicide is not protected from late blight.

Late blight - the same disease that caused the Irish potato famine in the 1800's - has been confirmed in potatoes in the Winkler, Carman, Carberry and Winnipeg areas, as well as in western Manitoba. Some of these cases were in "well-managed"fields where growers were rotating fungicides and spraying every five days.

Growers can view the disease forecast models online on Manitoba Agriculture's potato news website.