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:
Alternaria dauci
"Alternaria dauci" is one of two leading pathogens affecting carrots around the world. Most often found in temperate climates, the disease has been found in North America, the Netherlands, the Middle East, and even parts of Southern Asia and India. Carrot leaf blight is especially damaging in that its leaf lesions not only reduce photosynthetic area, but also weaken the leaves and petioles structurally. This makes mechanical harvesting of the carrot crop less efficient, and yields are even worse when blighted leaves have been exposed to heavy frosts.