I grow peach trees,(flat ones) and prior to spring and new leaves, the tree needs to be sprayed with copper sulphate. Do it again a few weeks later, and then put a large plastic bag over it entirely. This is the only way I got a decent crop. Plan ahead, make sure you cut the branches to fit the bag . Leaf curl is caused by the rain and wind, something we do well in the UK with. Hence, only idiots like me try to do the impossible....... Alternatively, grow it in a greenhouse. Just remembered, if you get leaf curl, and all the leaves eventually drop off, or you take them off, the tree may not look well, but don't give up, it will come back to life and new leaves without peach curl will come back later on in the season.