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:
Phytophthora infestans
The color of potato sign is white. People can observe "Phytophthora infestans" produce sporangia and sporangiophores on the surface of potato stems and leaves. These sporangia and sporangiophores always appear on the lower surface of the foliage. As for tuber blight, the white mycelium often shows on the tubers' surface.