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Posted 28 November 2011. PMN Crop News.

Potato Growers and Gardeners: Take Action to Prevent Late Blight

Source: Michigan State University Press Release.

East Lansing, Michigan (November 1, 2011)--This fall, the crops of small-scale potato producers and home gardeners are at higher risk for late blight if proper measures are not taken to prevent onset and spread of disease. Late blight is a serious potato infectious disease that can destroy potato and tomato plants. Early signs include small lesions on leaves that can grow into large, purplish-black lesions. Fields of many infected plants will give off a foul odor as tissues begin to decay.


Commercial potato growers already practice prevention techniques, but small grower and gardeners may need to take some time to ensure late blight doesn’t get a foothold on their crop. Crop diseases can find new homes if small producers aren’t careful.

“Aggressive fungicide programs adopted by large commercial producers help to prevent and control late blight outbreaks,” Jim Isleib, MSU Extension educator, said. “The disease can spread to tomatoes and potatoes, and it poses a serious threat to the Michigan potato industry.”

Uninformed or careless growers and gardeners who do not take actions to control late blight can increase the likelihood of infection to all potatoes in as much as a 50-mile radius.

“That could devastate Michigan’s $400 million potato industry and cause big problems in home gardens,” Isleib said.

Check plants daily and immediately uproot any that show signs of disease. Seal plants in a plastic bag and discard. Be careful not to reopen the bag; spores can be carried in the air.

To prevent the onset of late blight, Isleib suggests using certified seed potatoes and avoid replanting potatoes from last year. Any “volunteer” plants or seedlings that grow from last year’s unharvested or leftover tubers should be sealed in a plastic bag and thrown away.

Apply fungicides as directed by the label. The watering schedule should allow for a drying period during the day.

“In early spring, do not spread waste potatoes outside as they can survive this period with the disease. Check tubers regularly after harvest and discard infected ones in a sealed plastic bag.” Isleib said. “Infected tubers can decompose quickly, making it more difficult to catch the disease in action.”

Gardeners and small-scale potato producers should visit Michigan State University Extension News for more information about late blight and its prevention. This online resource features helpful articles about various topics submitted by MSU Extension experts throughout the state. Find MSU Extension News at

Also, visit for more information about growing potatoes in the home garden.

Beth Stuever
517-432-1555 x105