I have an infestation of Quackgrass in a lawn of TTTF and also in a separate lawn of a KGB/Rye mix. Is there anything out there that will kill the Quack without killing the grass? About 1/2 acre is affected and I dont want to kill everything with Roundup and start all over. I've looked into Certainty and Gordon's Q4 but Certainty kills fescue and Quack is not listed on the spec sheet for Q4. At $170 gallon I dont want to gamble on the Q4 working without someone telling me it will work. I'm looking for advice. Thanks to all.