Researchers watch tomato crops for late blight

Late blight is a potentially destructive disease of tomatoes, potatoes

While many farmers are worried about the drought’s effect on corn this year, University of Wisconsin-Madison researchers said a moisture-loving microorganism could be jeopardizing potato and tomato crops due to late blight.

Researchers said the fungus-like strain has arrived in upper and central parts of the state, and they’re keeping an eye on late blight’s movement in the coming weeks.

Late blight decimated Wisconsin crops in 2009. If undetected, researchers said late blight can do its damage in seven to 10 days by completely defoliating crops.

Documented reports of the strain include areas in northwestern Wisconsin, with it moving eastward, as well as reports in central Wisconsin.

Researchers said it may be too early to tell if it has reached as far south as Dane County.

“We don’t know that it’s not here yet,” said Amanda Gevens, UW-Madison vegetable pathologist. “Just because we haven’t found it doesn’t mean it’s not here already. We do know 40 miles surrounding an infected field can be a risk zone — those spores can move outward at that radius.”

If late blight is found on small-scale gardens, people are asked to destroy the plants by putting the plants in a black plastic bag, where the heat should kill the pathogen.

Larger operations should cut infected plants at the base, let them dry, or lightly till the plant to help encourage breakdown.

People can get their plants tested for free through the UW Department of Plant Pathology’s Disease Clinic. More information can be found at