dry rot

/D R AY1 R AA1 T/
noun
  1. 1

    The crumbly, friable decayed portions of wooden members of buildings, especially at or below grade, usually caused by a fungal infection.

  2. 2

    Any progression of decay, corruption, or obsolescence.

  3. 3

    A fungal infection which affects plants, in particular potatoes.

Source: https://en.wiktionary.org/wiki/dry%20rot