Late blight was found in three more potato fields in Michigan’s St. Joseph County on Monday, July 25. Initial genotyping confirmed isolates as US-23 by GPI isomerase testing. Mating type and Ridomil sensitivity are under way. The source of the inoculum is volunteer potato plants in a nearby sweet corn field.
Recommendations for late blight treatment remain the same as in previous reports posted by Michigan State University Extension, and include treating with one of the translaminar fungicides listed at the Michigan late blight risk monitoring website.
Conditions remain conducive for late blight in irrigated potato crops. Forecasts and disease severity value accumulations can be checked daily on the Michigan Late Blight Risk Monitoring website.
Source: Michigan State University Extension