This is a bit early for Japanese beetles. These might be rose chafers or false Japanese beetle. In any case, the control for any of the three is the same. Sprays of sevin when the beetles are actively feeding tends to work the best. Also effective is pyrethroid types (bifenthrin active ingredient, Ortho Bu-B-Gone). For both, check the label before you buy to make sure that it is legal to use it on peach, and to see the preharvest interval.