Is it planted in a lawn? Have you used an herbicide (like WeednFeed) on the grass? Have you or neighbors sprayed anything for weeds? It looks like something changed quickly.
Did you fertilize sometime before the new growth appeared? Since you've only had the tree since June and the new growth appeared midsummer, I'd also be looking at what you put in the planting hole. . . Excess fertilizer or conversely, bad soil.
