Hello,
This looks like damage from the 4-lined plant bug.  Here is more information on this pest: https://extension.umn.edu/yard-and-garden-insects/four-lined-plant-bugs  These insects are pretty quick moving, but by holding a bucket of soapy water underneath the branch while giving it a firm tap, you can get rid of quite a few. You can also spray an insecticidal soap or a spray containing pyrethrin, but make sure to spray when bees are not in the way, because these products will harm them.  That said, 4-lined plant bugs only feed a little while longer for this year, so perhaps you want to wait it out. You can just prune out the badly damaged foliage which will regrow soon enough.  

Thank you for contacting Ask Extension
Ruth