I am unable to open your photo from here (blocked at work) but my guess is you have aphids, which commonly affects the newest leaves. I've had a lot of issues with aphids on my Cortland tree this year. Look inside the curled leaves and you will find either little green aphids or little rosy/purple aphids. In either case, the aphids suck all the sap out of young leaves. The aphids are brought up the tree by ants, who enjoy tasting a chemical that the aphids secrete from their skin. So bottom line is that it is the ants' fault. The solution: Kill the ants for sure, plus kill the aphids and/or remove all the curled leaves with the aphids on them. You've already lost these leaves, they aren't helping the plant if they are all curled up, so you can safely pick them off the tree. Just keep checking the ground beneath the tree every few days looking for ant hills. Whenever you see ants, kill 'em. It's all their fault.