Updates provided by Amanda J. Gevens, Associate Professor & Extension Vegetable Plant Pathologist, Interim Co-Director of Wisconsin Seed Potato Certification Program, UW-Madison, Dept. of Plant Pathology
Late blight on potato has been confirmed in Wood County on 07-17-19. Sporulation was present but light on most leaves. Lesions were quarter sized on upper leaves. The clonal lineage/strain type of the late blight pathogen isolated from Wood County is US-23. This has been the most predominant type in the US in recent years and can be controlled with phenylamide fungicides like Ridomil.
Please consider antisporulant fungicides in the Wood County area and maintain 5 to 7 day spray intervals for prevention.
I have provided fungicide listings in past weeks. This link will help you access fungicide activity information.
Please contact me if you have further questions or reports.