Mycology

Deadly Galerina likes to grow on dead conifers.

Death Cap grows on tree roots, not sure if that counts.

There aren’t a ton of mushrooms that grow on healthy living trees I think, so it’s kinda hard to find a poisonous example but maybe Jack O’ Lanterns count. They can grow at the base of living hardwood trees. They won’t kill you but you will have a very bad time. I think there’s another closely related species that grows on both conifers and hardwoods.