Once a world enters hardmode, corruption and hallows being spreading at an alarming rate, including the underground. Grass, which grows on dirt, succumbs easily to both. Jungles and glowing mushrooms grow on mud and provide unique and valuable items. Will corruption/hallows destroy these if left unchecked? If they do destroy mud-based life, how can I preserve these fragile ecosystems?
Corruption will convert mud to dirt, but it won't grow corruption grass on any level too deep for regular grass. So the surface jungle will eventually be destroyed completely, but underground jungle and glowing mushroom farms should lose some areas to dirt at the edges, but then shrink no further.