Whats eating my Magnolia?

Hi all, bought a George Henry Kern magnolia and planted it earlier this year. Due to the weather the leaves went spotty brown and dropped off. Some lovely new leaves grew and were then decimated by something unknown. Iv dug it up to try to recover it. Any ideas what the culprit is?  The tree is more or less bare. The pics below show the last ‘full’ remaining leaves. The rest have been devoured