Yes, without a doubt your new flush got frost-bitten. But, the larger question is why did your tree lose all its mature leaves?? I would be more concerned about that issue, than the fact that tender new flush got frost-bitten. I see an awful lot of grass under your young tree. I would get rid of all the grass under the tree in about a 12' diameter, mulch and fertilize. Hopefully, by the time the next flush emerges, you'll beyond your frost times. If your temps threaten to dip below freezing, you'll want to try to cover your young trees with frost cloth, securing the bottom of the cloth completely, to cut off any loss of warm air. Stringing up Christmas tree lights (the incandescent type, not LED type) will also help prevent freezing.

Patty S.

Well I had added 2 fertilzer spikes in september and I had sprayed it with malathion since I saw some psyllids on the tree. Maybe those two things caused it to loose its leaves. I also have been watering it like ever other week