Wednesday, May 25, 2011

Tomato growers beware of late blight disease

Press Release from NYS Ag & Markets:

New York State Agriculture Commissioner Darrel J. Aubertine today alerted home gardeners and commercial growers of the potential introduction of late blight this growing season. Late blight is a plant disease that spreads rapidly from plant to plant in wet, cool weather that causes tomato and potato plants, primarily, to wilt and die.

“The exceptionally cool, damp spring we are experiencing throughout New York State this year heightens our concern for late blight,” the Commissioner said. “We saw the devastation it can do to a tomato crop in 2009, and we have already received reports of early late blight detection in neighboring states. Therefore, we want to remind our growers of this possible plant disease and alert them of the precautions they can take and how we, as a regulatory agency, are working to protect our plants.”

Last year, the Department initiated a concerted strategy to enhance the State’s detection and eradication efforts that involved training its horticultural inspectors, surveying plants at the retail level and in commercial greenhouses, and working with Cornell Cooperative Extension to conduct outreach and follow up in the field with growers and gardeners. This year, inspection of tomato plants has been a priority, and to date, more than 150,000 tomato plants have been inspected with no signs of late blight detected.

The Department has also been in regular communication with neighboring states and county Cooperative Extension offices regarding late blight. Just recently, we learned of two localized outbreaks – one on volunteer tomatoes in a greenhouse in Maine where they had problems with the disease in previous years; and one in a Connecticut greenhouse on potatoes and tomatoes that were likely introduced on the cut seed potatoes.

If late blight is detected in New York, the suspect lot of plants will be subject to quarantine upon initial visible diagnosis by a state horticultural inspector and the product sample will be sent to the Plant Disease Diagnostic Clinic at Cornell University for confirmation. If confirmed with late blight, the plants will be properly disposed of under state supervision and an investigation will be initiated in order to try and locate other possibly infected plants.

Late blight is a plant disease that mainly attacks potatoes and tomatoes, although it can sometimes be found on other crops, weeds and ornamentals, such as petunias, nightshades, and tomatillos. Late blight was a factor in the Irish potato famine in the 1840’s, during which millions of people in Ireland starved or were forced to emigrate. Late blight is caused by an oomycete pathogen that can produce millions of spores from infected plants, spreading readily with wet weather and high humidity. Spores travel through the air, land on plants, and if the weather is sufficiently wet, cause new infections. Once infected, plants may wilt and die within three days.

New York most recently battled late blight in 2009 – a strain that that was particularly devastating to tomatoes. Presence of the disease, combined with wet weather that season, led to a quick and devastating spread of the disease. Organic growers struggled with the disease as they have few approved control measures to use, and commercial tomato growers were challenged to apply crop fungicides in time to prevent the outbreak.

For more information about identifying late blight and how to control it, visit

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