I have had jackwagons tell me they are surprised to see me mix up the 1.25 oz rate of Certainty with MSO and Quicksilver, then boom the whole lawn. "dude, you are going to yellow the grass". I would imagine Celsius could be much worse, but I have never seen any damage from it. The jackwagons only use Sedgehammer because there is almost no risk of yellowing the lawn and it is sold in single dose boxes at garden shops. They cannot shop where I do. Fertilizing a couple of weeks before treating is yet one more step to get the most out of an application and lowering the risk of adverse reactions by the grass.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738