Impromptu Late Blight Open Day at Clarksville this Friday, Aug. 30

Willie Kirk, Michigan State University Extension, Department of Plant, Soil and Microbial Research -

With the recent appearances of late blight in Michigan, growers can visit the Late Blight Open Day and tour plots of potatoes infected with the genotype US-23.

Late blight (Phytophthora infestans, genotype US-23) has made an unwelcome appearance in southern Michigan this season. Michigan State University Extension has potato plots infected with this strain at the Clarksville Research Center in Clarksville, Mich. (get directions). As late blight has been uncommon over the past few years, it would be useful for growers and staff to view these plots in which late blight is developing. The plots will be open from 12:30-2:30 p.m. Friday, Aug. 30; however, no lunch will be provided.  

Several more fields in St. Joseph County have been reported with late blight. The genotype of the Phytophthora infestans isolate responsible for all late blight confirmations in potatoes and tomatoes crop has been the US-23 genotype. This was confirmed by GPI allozyme analysis. This genotype is Ridomil sensitive; however, the recommendations for treatment remain the same as in last week’s report and include treating with one of the translaminar fungicides listed on the Late Blight Risk Monitoring website.

Conditions remain conducive for late blight in irrigated potato crops despite the high temperatures experienced over the last few days. Forecasts and DSV accumulations can be checked daily at the Late Blight Risk Monitoring website. For the next five days, for example, most parts of Michigan have high risk forecast.

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

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).

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