August 14, 2004
From: ProMED-mail<promed@promedmail.org>
Source: The Miami Herald, 10 Aug 2004 [edited] <http://www.myrtlebeachonline.com/mld/miamiherald/business/9361500.htm>

Fungus threatens north east tomato crops

Just as tomatoes are ripening, a fungus threatens to rot the summer crop in the north east (of North America). Recent rainy months have created wet, humid fields ideal for late blight, a fungal disease that blackens tomato plants.

Symptoms appeared in Pennsylvania in early July: curled leaves with dark spots sometimes ringed by frosty white spores and dark greasy spots on the tomato fruits. In particularly bad cases, entire plants blacken and collapse, emitting a rotten odor. Penn State University plant pathology professor Alan MacNab has tracked the spread of late blight this season in Maine, New York, Pennsylvania, North Carolina, Michigan and eastern Canada.
New Jersey confirmed its lst case of tomato blight in August 2004 in Cumberland County. Wesley Kline, the county's extension agricultural agent, said all commercial tomato and potato growers in the state have been advised to spray with protective fungicides.

New Jersey farmers saw their production of processing tomatoes -- which go from the field to a jar -- drop by 30 per cent in 2003 after a bad bout of late blight, Kline said. New Jersey produces about 35 000 tons of processing tomatoes annually. Commercial fungicides are not available for back yard use, but home gardeners can help stop late blight's spread by pulling up and disposing of diseased plants in the garbage.

The late blight fungus spreads to both tomato and potato and is the same fungus species that caused the mid-19th century Irish Potato Famine. Tomato plants are susceptible to many fungal and bacterial diseases, said Mary Hausbeck, professor of plant pathology at Michigan State University.
"People need to remember that these microorganisms start out much like seeds ... and those seeds also need moisture to get started and infect the plants and cause spots," Hausbeck said. "Anything homeowners can do to keep those plants dry will protect the plant."

Infected tomatoes and potatoes, if eaten, pose no threat to humans. But late blight spreads quickly from field to field. "Once you walk into a field where it is, you have to be very careful. We wear plastic, disposable coveralls and boots, because you can transport it on your clothes," Kline said.

[byline: Jennifer Kay]

[Late blight is caused by the fungus _Phytophthora infestans_ and is a major pathogen of potato and tomato worldwide. Reports of tomato late blight are much less obvious in ProMED-Plant, perhaps because [compared with tomato] potato is a staple food crop that is consumed all over the world. There is little to no blight resistance in tomato, but scientists in Oregon have developed the cultivar "Legend," which is resistant to it.

Disease management involves appropriate cultural practices such as use of pathogen-free seed and irrigation management. Several recommended chemical protectants and systemic fungicides are also available.

ProMED-mail has no relationship with the developers of the cv "Legend."
Useful link: <http://info.ag.uidaho.edu/Resources/PDFs/CIS1051.pdf> - Mod.DH]