Wisconsin Potato and Vegetable Growers Association

Late Blight from St. Croix Co. is US-23

August 16th, 2016 | Posted in: Crop Updates, News


The tomato and potato late blight from St. Croix County was determined to be of the US-23 strain/genotype (and A1 mating type). This genotype is aggressive on both tomato and potato crops and can be controlled with mefenoxam/metalaxyl conventional fungicides (ie: Ridomil). This has been the most predominant genotype across the US in recent years. Growers in western and north-central Wisconsin should be on alert that late blight spores may be in the area risking health of tomato and potato crops.

Wisconsin commercial conventional fungicides for potato late blight control can be found at:

Wisconsin commercial conventional fungicides for tomato late blight control can be found at:

Frequently asked questions and organic control of late blight info:

Best regards,

Amanda Gevens
Associate Professor & Extension Specialist
Potato & Vegetable Pathology
Plant Pathology Department
University of Wisconsin-Madison
Madison, WI 53706
[email protected]

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