I usually just steer clear of Eerie biomes but have learned to see the signs of fledgling problem areas. The "burial mounds" are also sources of taint, as are the new obelisk structures.
Since I like to live in Natura Redwood trees sometimes I have to put down roots (sorry for the pun - not!
) near an Eerie location. In those cases I search for my nearest Magical forest to get Silverwood saplings. Recently I've had fairly good luck just finding one or two on the ground but there are special tools (thaumic shears?) to collect the leaves and increase the chances of saplings.
I plant the sapling(s) on the border of the taint between it and my tree and watch the Magical forest slowly take over, wiping out the Eerie biome.