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Taking the bite out of late blight

Media contacts: Dr. Jean Ristaino, professor of plant pathology, N.C. State University; 919.515.3257 or
Dr. Ryan Boyles, state climatologist and director of State Climate Office of North Carolina, 919.513.2816 or

North Carolina State University scientists will be heavily involved in a national effort to help farmers better manage a plant disease called late blight, which can decimate tomatoes and potatoes.

Dr. Jean Ristaino, a professor of plant pathology in the College of Agriculture and Life Sciences at N.C. State, and Dr. Ryan Boyles, state climatologist and director of the State Climate Office of North Carolina, which is located on N.C. State’s Centennial Campus, are part of a $9 million, 5-year U.S. Department of Agriculture effort to give farmers better tools to use in dealing with late blight. The effort is being led by the University of California at Riverside but will involve scientists across the nation.

Ristaino said the N.C. State effort will focus on the development of an online national late blight reporting and alert system. This system, which will show farmers late blight outbreaks across the nation, will include what is known as decision support information on how best to deal with the disease.

Late blight, which is caused by a pathogen called Phytophthora infestans, infects American tomato and potato crops every year, Ristaino explained, but various factors, including weather, determine whether the disease causes significant crop losses from year to year. The disease was particularly bad in 2009, she added, when cooler than normal temperatures and abundant rainfall helped spread late blight. In 2009, late blight destroyed much of the tomato production in the northeast U.S.

Ristaino said growers can protect their crops from the disease if they apply fungicide prior to a disease outbreak and if they apply the correct fungicide. The system that Boyles and Ristaino are developing is designed to give farmers the information they need to protect their crops from the disease.

The state climate office will develop an online map that will use information from monitoring teams around the nation to locate late blight outbreaks. Ristaino said that on the East Coast, the disease typically begins each spring on tomatoes in Florida and then spreads to other areas by weather events. The spores that cause the disease can be carried on the wind, although Ristaino said that in 2009 most pathogen movement was the result of  the shipment of infected plants from one part of the country to another.

The severity of the disease also depends to a large degree on the strain, or type, of late blight. Working with scientists at Cornell University in New York, Ristaino will determine the type of late blight found in farmer’s fields. Ristaino said 24 different late blight strains, or genotypes, have been found in the United States, and some of these strains tend to damage one crop, either tomatoes or potatoes, more than the other. At the same time, different strains are more or less susceptible to different fungicides. In 2009, five different stains were found on tomatoes and potatoes, but one particular stain, US-22, did most of the damage, she added.

When reporting teams across the country find the disease, they will send samples to Cornell and N.C. State and to Oregon State on the West Coast. At N.C. State, Ristaino’s lab will determine the disease genotype. This information along with the location of the disease will be available through the online map. The late blight website will also include information on how best to protect crops from the disease. Ristaino added that as she and other scientists identify late blight strains they should be able to track the development of strains that are resistant to various fungicides, information that should be extremely helpful in aiding farmers in managing the disease.

Ristaino said the project also includes an educational component. Summer internships will be available to undergraduate students who wish to work on the project.

The reporting and alert system is expected to be operational for the 2011 growing season, and Ristaino said she expects to begin receiving disease samples in early May. She added that the disease typically moves up the East Coast as the growing season progresses. Late blight is usually found on North Carolina potatoes in June, while it’s usually found on tomatoes in western North Carolina in late July and August.

This year, farmers should be better prepared than in the past when late blight makes its annual appearance.

Written by: Dave Caldwell, 919.513.3127 or