dry rot

noun3

1. •
   The crumbly, decayed portions of wooden members of buildings, especially at or below grade, usually caused by a fungal infection.
2. •
   A fungal infection which affects plants, in particular potatoes.
3. •
   (figurative) Any progression of decay, corruption, or obsolescence.

   • Therefore I am like a moth to Ephraim, and like dry rot to the house of Judah. — 1952