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
A second confirmation of late blight has come in from La Crosse County Wisconsin from tomato. The disease was confirmed by DATCP and was determined to be of the US-23 Phytophthora infestans clonal lineage by Dr. Monica Chen of my UW-Vegetable Pathology Laboratory in Madison. The first confirmation was from Wood County (US-23 on 17 Jul) and disease did not appear to spread beyond the initial source, which has since been killed.
Antisporulant fungicides are recommended for growers of tomatoes and potatoes in the region surrounding La Crosse Co.; additionally, as air movement prevails from west to east (and northward), growers in central and northern WI should be proactive in protecting susceptible crops with effective fungicides. Please see link below to registered fungicides for late blight in WI.