I agree, it looks like the curcs got in there. Surround takes quite a bit of practice to get effective control with, it is not like other sprays. Since it is only irritating them you need to constantly have a good coat on or you will get damage. See my spray guide at
where I wrote a whole bunch of tips on Surround spraying.
It has been an odd curc year for me, lots of rain but lots of cold as well so the activity overall has been lower than usual.