In addition to the previous identification of late blight in western Maryland, this disease has now also been found on the eastern shore of Virginia on potato in the field. This isolate was identified as genotype US-23, which is in the same group as the Maryland pathogen. US-23 isolates can infect both tomato and potato.
While common weather patterns rarely track weather from eastern Virginia to Kentucky, potato and tomato growers should remain vigilant with their protectant fungicide programs to be best-prepared. Mancozeb, chlorothalonil, and copper are protectant fungicides that should prevent initial late blight infections in the field. As always, if late blight is suspected, contact local Extension agents who will prioritize diagnosis of the disease. Late blight progresses extremely quickly through fields under rainy conditions, and the most effective control is to protect crops from becoming diseased.
For more information on late blight of tomato and potato, including the ability to sign up for alerts for your farm, see the USABlight website.
By Emily Pfeufer, Extension Plant Pathologist