Blight today has become increasingly popular to refer to deterioration of a region or city. However, using this term in its exact sense, there are at least 2 senses of it in discussion, in the effort of doing so being as constructive as possible.
Blight can refer to describing a disease. For example, the blight that caused the trees to go back may have been caused by acid rain.
Blight can refer to conditions of a city. Simply saying 'urban blight', could leave room for the cliche to be unclear as to what exactly happened to the city or region, or were the hopes dashed? For example, did buildings deteriorate due to age, or were they purposely damaged.
That may leave to identify, prevent, and repair blight, as it relates to city infrastructure conditions.