Hi Les, your profile doesn't say what country you are in.
But worldwide, that leaf damage is usually caused by gall wasp or some type of leaf cilyd.
Remove and bin the affected leaves then spray with a pyrethrum spray being sure to get under every leaf and all over every branch.
Sometimes a pyrethrum spray won't cut the mustard and you are forced to use chemical. Actually pyrethrum itself is non-specific and kills every insect, even the good guys. But its not systemic.
Although having given that advice I also must tell you the eggs were laid while the plant was dormant.
So if it is a brand new tree that you just purchased and planted, blame must go to the supplier for not spraying at the appropriate time to prevent this type of insect attack.
However if you've had the tree for a while, then while the tree is leafless and dormant in winter, its the time to spray for a whole host of bugs and diseases that attack fruit trees.
Different bugs and diseases for different families of trees but if you don't spray and put out baits, you will have unhealthy trees that don't flower or produce little or no fruit.