Blight

Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism (oomycete) that causes the serious crop disease known as late blight or potato blight. The Early blight caused by Alternaria solani is also often called "potato blight". Despite its resemblance to true fungi, morphological and molecular classification places this organism among the Stramenopiles; as their cell walls are made of cellulose instead of chitin, and they reproduce through swimming spores, they are evolutionary and functionally closer to algae and diatoms. The organism infects various members of the Solanaceae family, such as the potato (Solanum tuberosum) and the tomato. The pathogen favors moist, cool environments: sporulation is optimal at 12–18 °C (54–64 °F) in water-saturated or nearly saturated environments, and zoospore production is favored at temperatures below 15 °C (59 °F). Lesion growth rates are typically optimal at a slightly warmer temperature range of 20 to 24 °C (68 to 75 °F). Historically, late blight was a major factor in the 1840s European, the 1845–1852 Irish, and the 1846 Highland potato famines.