By George Kuepper and Preston Sullivan
NCAT Agriculture Specialists
March 2004
©NCAT 2004
Abstract: New strains of late blight have emerged in recent years, making potato production especially
challenging. Several nonchemical options are available for managing this disease, including cultural
practices, some varietal resistance, and alternative sprays that discourage disease development.
Late blight (Phytophthora infestans) is a fungal disease that attacks the leaves, stems, and tubers of potato plants. In the 1840s, P. infestans caused the Irish potato famine, when a million people starved and another million and a half emigrated out of Ireland (1). In recent years, highly aggressive strains of this disease—many insensitive to popular synthetic fungicides—have surfaced and created new challenges for potato and tomato producers (2).