Caused by the pathogen Phytophthora infestans, late blight was identified on a tomato plant that had been submitted to the University of Wisconsin-Madison's Plant Disease Diagnostic Clinic. Since then, two additional cases have been identified in southern Wisconsin, the state agriculture department said.
Late blight was the biological cause of the Irish potato famine from 1845-1852. Under the right conditions, late blight will spread rapidly, killing plants in one to two weeks.
"Gardeners and growers need to know what late blight looks like and to take proper steps to protect your plants from the disease," said Amanda Gevens, UW-Madison plant pathologist.
Late blight lesions can occur on leaves, stems or fruit. Lesions usually begin pale green in color, eventually turning brown to black and appearing somewhat greasy.
If you have late blight, destroy infected plants to prevent further spread of the disease. Growers with small numbers of plants should pull and bag plants for removal. Large plantings should be tilled down thoroughly with tractors.
