dry rot

Noun

dry rot (uncountable)

1. The crumbly, decayed portions of wooden members of buildings, especially at or below grade, usually caused by a fungal infection.
   • They are, for the most part, low-roofed, mouldy rooms, where innumerable rolls of parchment, which have been perspiring in secret for the last century, send forth an agreeable odour, which is mingled by day with the scent of the dry-rot, and by night with the various exhalations which arise from...1836, Charles Dickens, The Pickwick Papers., archived from the original on 11 Aug 2014
2. (figuratively) 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, RSV, Hosea 5:12
3. A fungal infection which affects plants, in particular potatoes.