This week Plant Pathologist Kelly Ivors found and confirmed late blight (by microscopic examination) in one small shaded area of a conventional tomato field in Henderson County. We have not been able to confirm its presence anywhere else in the tomato production areas of NC this summer, so I believe this is the start of the tomato late blight epidemic in WNC. We've had some rains recently and I'm sure it's out there elsewhere now, or soon to arrive.
Without proper preventative measures, late blight can completely defoliate and destroy a crop within one to two weeks. The disease can be severe on tomatoes grown in the mountains of North Carolina, as well as in late plantings in the Piedmont.
The first symptoms of late blight on tomato leaves are irregularly shaped, water-soaked lesions on lower leaves. During high humidity, white cottony growth may be visible on underside of the leaf. As the disease progresses, lesions enlarge causing leaves to brown, shrivel and die. Fruit lesions appear as dark, greasy spots that eventually turn a chocolate brown color, and can enlarge to the point of encompassing the entire fruit.
Refer to this website for more details on the symptoms of this disease. The application of fungicides plays a significant role in the control of late blight. Fungicides containing copper, chlorothanonil, or mancozeb are recommended for treatment in home gardens.