NDSU Potato Blightline 12 August 2019. More good news. Late blight is NOT reported in ND, MN or MB. Late blight is reported in multiple locations in WI. The cool weather, closed rows, rain and morning dew are ideal conditions for late blight. The spore-trapping network in ND and MN has not yet detected spores of P. infestans, the cause of late blight. We commonly see first late blight infections in the field in early August, so it is important for all growers and consultants should be actively scouting fields for late blight, especially near pivots, shelterbelts and other areas that stay wet for longer periods.