Potato late blight reports in Northern United States in 2014

There have been reports of late blight on tomatoes and potatoes in Florida over the last two months. Many areas in Michigan are now in the yellow zone for Disease Risk Severity.

No late blight has been reported yet in Michigan, although there have been reports of late blight on tomatoes and potatoes in Florida over the last two months. As of today, June 18, 2014, there have been no new reports in the last 10 days. The US-23 genotype (A1 mating type and metalaxyl-sensitive) of Phytophthora infestans was diagnosed in all cases.

As of Wednesday, June 18, there remains variability in the Disease Risk Severity accumulations for late blight across the state with many areas now in the “yellow zone.”  All crops in yellow zone areas that are emerged should be on a seven-day schedule of protectant fungicide. Disease Risk Severity Values are updated daily and stations across Michigan can be compared at the Late Blight Risk Monitoring website. The accumulations were initiated on May 1, 2014. You can accumulate late blight risk based on emergence date at all Michigan State University Enviro-weather sites across the state.

Current recommendations for fungicides for late blight, early blight and brown leaf spot can be found in the Michigan State University Extension Bulletin E312, “Insect, Disease and Nematode Control for Commercial Vegetables,” on page 116. There is also a link for recommended fungicides and application rates and intervals based on late blight risk at the Late Blight Risk Monitoring website. Clicking on the product link takes you directly to the TIRMS website and the product label.

Dr. Kirk’s work is funded in part by MSU‘s AgBioResearch.

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