On August 18, results of spore trap filter analysis were positive for late blight for the Alliston, Ont., area, says Eugenia Banks, a potato specialist with the Ontario Potato Board. Late blight was found in a field near Alliston on August 14, she says.
“There was a delay of at least 10 days between plant infection and catching spores in the spore traps,” says Banks. “One of the reasons for this delay could be related to the negligible white fuzzy growth of late blight on the underside of infected leaves,” she says.
Furthermore, producers in the area will need to apply a protective spray and monitor closely for spread to other areas, she says.
Larry Kawchuk, a research scientist at Agriculture and Agri-Food Canada’s Lethbridge Research and Development Centre, conducted a preliminary assessment of the late blight strain identification, which indicates the strain appears to be US 23.
US 23 is still susceptible to Ridomil, says Banks. “Ridomil plus Kocide is a good tank mix for fields that will not be top-killed soon,” she says.