WOOSTER/COLUMBUS, Ohio - Late blight, a potentially devastating disease of tomato and potato, has been found in Ohio and may threaten home gardens and commercial operations alike - particularly as wet, cool weather conditions this week in most of the Buckeye state will create a favorable environment for the spread of the fungal pathogen that causes this disease.

Responsible for the Irish potato famine of the 1840s, late blight has caused widespread crop damage across the United States and Canada since 1990. If left unmanaged, this disease -- which is transmitted via spores -- can result in complete destruction of tomato or potato crops. Ohio is one of the country's top tomato growers, with annual production valued at more than $130 million for both fresh and processing tomatoes; the state also produces some 100 million pounds of potatoes a year.

Late blight thrives under weather conditions such as those expected in most of Ohio this week: nights in the 50s F and days in the 70s F, accompanied by rain, fog or heavy dew. Under those conditions, lesions may appear on leaves within three to five days of infection, followed by white mold growth soon after. Spores formed on the mold are spread readily by irrigation, rain and equipment. These spores can also be easily dislodged by wind and rain and can be blown into neighboring fields within five to 10 miles or more, beginning another cycle of disease.

"Now that the disease has showed up in Ohio, it is likely that it will affect a lot of home gardeners," said Sally Miller, a plant pathologist and vegetable crops specialist with the Ohio Agricultural Research and Development Center (OARDC) and OSU Extension. "If these home gardeners don't control it well, a lot of inoculum (spores) may be floating around if weather conditions (cool and wet) favor the disease. This inoculum can be a threat to commercial tomato and potato producers."

The current outbreak was first reported on tomato plants sold at garden centers and on tomatoes at home gardens and farms in New York, Virginia and Pennsylvania; it was also found on potatoes from Pennsylvania. In Ohio, late blight was confirmed in a non-commercial tomato sample on June 25. Because infested tomato plants were traced to a garden center chain that has numerous stores across Ohio and the country, diseased plants may have already turned up in people's vegetable gardens.

SOURCE: Ohio State.