Michigan State University Extension officials have confirmed late blight in a potato crop south of the Michigan-Indiana border and are recommending growers treat their crops with a translaminar fungicide.
Testing is ongoing, but Extension agents said in a notice that initial experiments indicate the blight is an “aggressive isolate.” They reported the source had not been determined as of July 6. Agents also detected late blight in southern Michigan in 2013.
“The recent weather conditions and winter soil temperatures favored the re-appearance of this destructive pathogen in Michigan, particularly in the region south of Lansing,” according to the Extension notice.
The disease is caused by water mold, according to the Extension service, and the pathogen favors moderate temperatures between 60 and 80 degrees Fahrenheit accompanied by high humidity and frequent rains.
“Under such conditions, the disease can spread extremely rapidly and has the potential to completely defoliate fields within three weeks of the first visible infections if no control measures are taken,” according to the notice. “In addition to attacking foliage, (it) can infect tubers at any stage of development before or after harvest, and soft rot of tubers often occurs in storage following tuber infections.”
Growers can monitor disease forecasting on the Internet at www.lateblight.org.
Source: The Grower