Tree blights that are hiding and motionless should actually use the game’s “appear as furniture” system to appear fully as dead trees, so that even if you farlook them they just show up as “dead tree”. Currently they have the same ASCII glyph but appear as “tree blight” in farlook, allowing you to trivially scan the map and confirm any suspicious-looking dead trees to be blights or not. This would also enable the tree blight tile to be distinct from the dead tree tile.

Zapping undead turning at a dead tree should turn it into a living tree, or an ent (for the occasional dead tree that is actually a dead ent). If it’s a tree blight, it could either do nothing or harm the blight, depending on whether one considers the blight to be an undead tree.

Draugrs should be able to bite trees to turn them into dead trees.

Attacking a dead tree with a weapon of fire, or an artifact with fire damage, will burn up the tree.