Jaime Willbur, Assistant Professor, Potato & Sugar Beet Pathology Program, Department of Plant, Soil, and Microbial Sciences, Michigan State University
We have confirmed two reports of potato late blight in two separate field areas of Montcalm County, Michigan detected September 6 and September 7. Active sporulation was observed in both areas and infected fields have been chemically vine-killed. Isolate genotyping is in progress and additional information will follow as will an accompanying MSU Extension news article. Both detections were reported by conscientious crop consultants and immediate measures have been taken to reduce further spread.
Current late blight risk is medium in Michigan, however, some areas have experienced favorable conditions in the past several weeks due to more frequent and heavy rain events. Late blight forecasting in Michigan is available through our website: https://www.canr.msu.edu/psbp/resources/disease-tools/late-blight-disease-forecast. Preventative foliar programs and diligent crop monitoring is strongly recommended.
No other nearby states have reported late blight. In other areas, tomato late blight was reported in Ottawa County in Eastern Ontario on July 26 (https://onvegetables.com/2022/07/26/late-blight-update-july-26-2022/), in Cocke County, Tennessee on August 5, and in Haywood County, North Carolina on August 18. A map of current U.S. late blight observations can be monitored at https://usablight.org/map/.