|Yesterday I found 3 large mushroom-like growths (~4' by 6|
|Centipedes and millipedes are distant relatives of lobsters, crayfish and shrimp. Unlike their marine cousins, centipedes and millipedes are land dwellers, but they do prefer moist habitats or areas of high humidity. Millipedes feed primarily on decaying organic matter, but may attack roots and leaves of seedling plants. Controlling centipedes and millipedes outdoors includes removing objects that provide harborage such as trash piles, rocks, boards, leaf piles, compost piles and similar materials.
I hope that the description of the mushroom growth is incorrect. A mushroom four-feet by 6-inches is quite a large specimen! Mushrooms grow in decomposing organic matter. It could be getting its nourishment from dead tree roots or other buried wood, or from dead or dying plant roots. The millipedes probably arrived because of the decomposing organic debris. So, remove the mushroom growth, dig up and dispose of any decaying wood or roots, and the millipedes should leave the area, as well.