Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. It is simply 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:
On leaf tissue, symptoms of blight are the initial appearance of lesions which rapidly engulf surrounding tissue. However, leaf spot may, in advanced stages, expand to kill entire areas of leaf tissue and thus exhibit blight symptoms!