Late blight is a plant disease that attacks both potatoes and tomatoes.
Late blight caused the Irish potato famine in the 1850's, during which millions of people in Ireland starved or were forced to emigrate. Entire potato crops rotted in the field or in storage because of late blight infection. Late blight is caused by a fungal pathogen that survives from one season to the next in infected potato tubers. This fungal pathogen is well known for its ability to produce millions of spores from infected plants under the wet weather conditions that favor the disease. Later in the season, spores from infected potatoes and tomatoes in nearby fields or gardens can travel through the air, and if the weather is sufficiently wet, cause new infections.