Mildewing

Mildewing is a corruption-like status that takes place in the Glowing Mushroom biomes after unlocking War Mode. Glowing Mold can spread to the surface, convert dirt to mud only to spread in it, and the Truffle NPC cannot live near it.

Glowing Moldy Grass and Giant Moldy Trees appear neon green, instead of the usual blue. Stepping on Glowing Moldy Grass causes 3 debuffs: Weak, Withered Armor and Withered Weapon. It also decreases jump height, but increases speed for both players and enemies.

If the Truffle touches moldy grass, he will instantly be slain. However, you can buy Moldy Powder from him, which he sells during a Blood Moon, combine it with Gold Dust to make Gold Mold powder and throw it on him to upgrade him to the Gilded Truffle, which can live in any Biome and will not be slain from spreading mold. He will also sell Golden Mushroom Seeds, which will, among other effects when planted, fight back against Glowing Mold.

Normal Glowing Mushroom Biome enemies will not be affected by mold, other than becoming confused. The Mushi Ladybug, however, will become slower on ground.

To stop mildewing, using a Clentaminator with the Dark Blue Solution is always a good option. Defeating all Hardmode bosses when battled at once will also stop and remove mold entirely. However, this may still be brutal in early War Mode. This does not include event bosses such as the Ice Queen, although they do have to be defeated.