Surround the field with wheat to keep wind-blown spores from entering. Use adequate nitrogen levels and low phosphorus levels to reduce disease severity. See current recommendations for chemical control measures. Late Blight Late blight of potato is a serious disease caused by Phytophthora infestans . It affects potato, tomato and, occasionally, eggplant and other members of the potato family.
Late blight is the worst potato disease.
It is famous for being the cause of the 1840s Irish Potato Famine, when a million people starved and a million and a half people emigrated. Late blight continued to be a devastating problem until the 1880s when the first fungicide was discovered. In recent years, it has reemerged as a problem. It is favored by cool, moist weather and can kill plants within two weeks if conditions are right. Leaf spots begin as small, pale to dark green, irregularly shaped spots.