Looks like Spittlebugs and worm casings to me too.
I use Bifenthrin for spittle bug control and works for grubs too.
Spittle bugs are a b_tch though. You need to do a granular treatment and spray, and then likely spray again in two weeks and maybe again two weeks later. Spray early or late while they are hopefully settled in [and feeding on your grass ;-)].
Ortho Max is retail/box store Bifenthrin.