Hey Suzie...This can be a number of things, but whenever I hear (or read in this case) the words "leaf curl", I quickly think of either leaf curling worms or aphids. Both are pests. On the other hand, these pests usually will not cause the leaf to completely dry up and die though. I think it would be best if I saw a photo. You can attach a photo via email to psplants at plantsense dot com. I will check out the photo and hopefully I can give you some good advice. Look forward to seeing your email. Cheers...Dr. Robby