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Late blight on a stem. Photo: Eugenia Banks

Late Blight Confirmed in Wisconsin

In the Wisconsin Potato Newsletter,  Amanda Gevens wrote: Late blight on potato has been confirmed in Wood County this afternoon. We have a sample on campus in UW- Madison Vegetable Pathology and my technician will type this first thing in the morning so that we have an understanding of the clonal lineage (strain),  and likely character and mefenoxam (metalaxy-Ml) resistance status.  Sporulation was present but light on most leaves.  Lesions were quarter sized on upper leaves.”

The Ontario Potato Board’s spore traps located in Simcoe and Dufferin Counties detected low levels of late blight DNA earlier this week. The PCR analysis was conducted by A&L Biologicals.  This laboratory has state-of-the-art PCR equipment that is very sensitive and capable of detecting very small amounts of late blight DNA, perhaps only a couple of spores per filter.

Late blight has not been found in Ontario yet, but the weather has been variable.  This week, some areas got rain, others nothing.  Irrigation has been the order of the day in Simcoe County. Irrigation also provides favourable conditions for late blight.

Monitor your fields regularly, specially areas prone to late blight: low spots, compacted areas, rows close to tree lines, field edges along creeks or ponds and pivot wheel tracks.

Keep your fields protected — an once of prevention is worth a pound of cure!

If you have any questions please contact Eugenia Banks at

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