Late Blight, Phytophthora infestans, is an oomycete pathogen that can infect and destroy the leaves, stems, fruits, and tubers of potato and tomato plants. The disease spreads quickly in fields and can result in total crop failure if untreated. It is best known for causing the Irish potato famine of the 1840s. Spores can spread by irrigation, equipment, wind, and rain and can be blown into neighboring fields within 5-10 miles or more.
Potato, tomato, petunia, and nightshade.
Successful management of late blight relies on an integrated approach, including: (1) removing sources of the pathogen and planting only healthy plants; (2) using resistant cultivars; (3) scouting locations where late blight might appear; and (4) using weather forecasting to modify the frequency of fungicide application.