...To get rid of grubs cheap n easy with no poison involved, go to the dollar store and buy a large box or 3 of powdered laundry detergent. Sprinkle all over the area you suspect there are grubs and turn on the water sprinkler for an hour.
The whitening ingredient, I'm trying to remember the name but I think its Sodium percarbonate, AKA, sodium carbonate peroxide, and that will drive them up to die quickly. Dont use too much water too fast, just enough to mimic a 1/4" or 3/8" of rain. I have done this and it worked overnight.