She and her team also are developing new diagnostic tools, using recombinant DNA techniques made possible by advances in molecular biology, that allow more rapid and accurate detection of the pathogen's presence in plants before they are placed in storage or planted in fields. NC State has applied for a patent on the technique and is working with Agdia Inc., a commercial diagnostic company located in Elkhart, Ind., on licensing of the technology. Until recently, severe outbreaks of the Phytopthora infestans fungus had been infrequent in most developed nations, thanks to reliable means of control provided to farmers by fungicides and disease-resistant potato varieties. Reports by NC State extension plant pathologists indicate that since 1991, annual epidemics of late blight have affected tomato crops in the state's western counties. The state's potato-growing regions near the coast have a climate less favorable for disease development, but when conditions are favorable, an uncontrolled epidemic can result in 100 percent losses, as occurred in 1995.
Late blight can destroy a crop in a matter of weeks.
Within days of the first telltale brown specks on leaves and stems, an entire field can look as if it has been burned. Spores from infected plants can be carried hundreds of miles by the wind to land on healthy potato plants. Potatoes are one of the world's four leading food crops, along with rice, wheat and maize. Sexually reproduced fungicide-resistant strains of late blight pose an especially great threat in developing countries, where control measures may be nonexistent or too costly to use. Work to evaluate new fungicides is under way by NC State researchers and extension specialists.