Blight
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are:
Frances Meehan Latterell
The idea that toxins caused plant diseases goes back to papers in 1886 and 1913, but Latterell's 1947 paper and a 1955 paper by H. H. Luke gave the first proofs. Latterell showed that fungus creates a toxin which causes the same symptoms as Victoria blight on the same oat cultivars which suffer from Victoria blight, but causes no symptoms on cultivars which resist the blight. Luke went on to show that different strains of the fungus create different levels of toxin, which correlate with the effects seen in oats.