It's mold. It's yellow. It has nasty spores.
Detect: Per-based Naturalist.
Disarm: Burn the whole colony. This will make all kinds of smoke, which will likely make its own problems for the burner.
Circumvent: Automatic (don't bother the mold).
Effects: Resist HT or take 2d HT damage.
Notes: Bothering the yellow mold spores will trigger the trap. Most to the time, this means walking through a patch of them or jostling furniture covered with mold.