We planted a magnolia a couple of weeks ago and it doesn't look very good now. We pulled away the mulch and the top looks wet. The soil is clayish. We not sure what's going on. Any help/suggestions of how to salvage it would greatly appreciated. I also attached some pics for reference.
Certified GKH Gardening Expert
Yes, this does appear to be a fungal infection from remaining in over-wet soil for too long. If your area is prone to heavy rainfall, then I would recommend removing the mulch until it dries out some.
You can attempt to correct this using wettable sulfur and dolomitic lime. This will kill off any infection that is able to be killed, while reconditioning the soil back to a more suitable condition for the tree.
Make sure to only water if the soil is completely dry. These are fairly drought tolerant, and will prefer to dry out between waterings if possible.