How long has it been in the ground? Do you use a soaker hose around your tree to give it a good soaking during the summer when things get dry?

Has anyone at your home or a neighbor sprayed or put down any kind of herbicide/glyphosphate? Overspray on a breezy day could have affected your tree as does weed 'n feed products.

If you could post a photo, I'm sure there are people here who could give you a better answer than mine. But, without seeing the problem, it is hard to give advice.

You might also want to contact a local certified arborist to come look at it. They will better be able to give you advice on what should be done to care for your tree.

Jourdy, Sorry to hear about your magnolia. If it is on only one side of the tree, then it is quite possible that side may have been accidentally sprayed with a herbicide. However, a photo will speak a thousand words. My magnolias, last year, developed brown spots and finally the leaves died down. It was a fungal disease. I sprayed Neem oil solution on all of them and helped survive. This happens in early spring. Better yet pl share a few fotos.

What type of magnolia is it? The care of a Japanese or Chinese Magnolia is very different than Southern Magnolia. As said above, either the type or a photo would be very helpful.

I believe that the OP never came back after asking the question last year.

Hey, hey! Thanks for pointing out the date. I missed that.