Late blight is responsible for the great 1847 Irish Famine and is perhaps the most notorious example for phytopathology. Late blight is a major threat to important crops around the world and is a driving force for new fungicide development.
Late blight is documented in all members of the Solanoideae plant family, but potatoes and tomatoes have higher tendencies of getting infected.
Late blight is often misrepresented as a fungus; however, it is an oomycete, a fungus-like organism similar to algae.
Cool weather (15-25 C) and extended periods of high humidity, as a consequence of rain and fog, can result in a late blight epidemic. The entire potato and tomato fields be severely damaged within a few days or even destroyed within a matter of 2 weeks.
Late blight symptoms include the spread of brown to black lesions on leaves surrounded by a thin halo of brighter pigmentations. Green fruits are more vulnerable to infection and could become marble-brown in appearance and the fruit becomes hard. In high humidity conditions, gray to white “fluff” will appear around the edges of darker lesions.