Answer: The active ingredient in Casoron is Dichlobenil. The product is a pre-emergent herbicide designed to keep weed seeds from germinating. It probably won't kill your grass, but it may inhibit new grass seeds from sprouting. I would try mowing it with a bag attached to the mower (to hopefully suck up the encapsulated herbicide). Be sure to trash rather than compost the clippings.
Best wishes with your lawn!
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