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Late blight on potato leaf
Late blight on potato leaf

Photo of Phytophtora infestans, or late blight, on a potato leaf, by Howard F. Schwartz
https://commons.wikimedia.org/wiki/File:Late_blight_on_potato_leaf_4.jpg
via a Creative Commons license.
https://creativecommons.org/licenses/by/3.0/deed.en