Michigan Late Blight Update

Published online: Oct 03, 2019 Articles, Fungicide Jaime Willbur & Lee Duynslager
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Source: Michigan State University Extension

Potato late blight has been confirmed in Clinton County, Michigan, in a home garden plot. Symptoms were first detected Sept. 20, 2019. Samples were submitted to the Michigan State University Potato and Sugar Beet Pathology on Oct. 1. Typical water-soaked lesions with gray, fuzzy undersides were observed (Photo 1) and Phytophthora infestans sporangia were confirmed (Photo 2). Genotype testing is in progress.

In Michigan, most commercial potato fields are either undergoing harvest or have been vine-killed to prepare for harvest. However, late-planted fields with green canopies may still be at risk for infection.

This summer, late blight was confirmed in several neighboring areas, including 14 counties in Wisconsin, 10 counties in New York and nine counties in Pennsylvania. All tested isolates were determined to be the US-23 genotype of P. infestans. Late blight was also reported in Tennessee, North Carolina, Florida and Washington. Visit the USA Blight Outbreak Map for more details.

Please contact MSU Potato and Sugarbeet Pathology at (517) 355-3863 to report potential late blight detections or visit the MSU Extension website for more information.