To date, late blight has been confirmed on potato in four counties, Barron, Adams, Portage, and Oneida. Infection did not appear to come from seed or volunteers. Rather, it appears that inoculum came into fields aerially. While Wisconsin has experienced drought in many counties this summer, sporadic and isolated rain storms did come in from the west and create moisture conditions favorable to late blight. We have had no reports of late blight on tomato in Wisconsin so far this season.
Wisconsin Vegetable Production