How to kill crabgrass in lawn that has cool and warm season grass?

Not sure there is a post-emergent herbicide that handle crabgrass in both warm & cool season grasses, other than spot spraying each plant with glyphosate, but going forward you need to start applying a pre-emergent herbicide annually in the spring such as dithiopyr (Dimension) or Prodiamine (Barricade) before soil temperatures warm to 55 F, which is the germination temperature of crabgrass seeds. Those pre-emergents are very effective in controlling crabgrass & numerous other annual lawn weeds.

Tennessee Cooperative Extension Service can provide you the optimal time for application for your county in east TN.

If I just want to preserve the Bermuda and say screw the bluegrass in these spots, what herbicide is safe for Bermuda that kills crabgrass?

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If I just want to preserve the Bermuda and say screw the bluegrass in these spots, what herbicide is safe for Bermuda that kills crabgrass?

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Well, some on this board might suggest the herbicide MSMA that use to be labeled for use on residential lawns but is no longer primarily b/c of the arsenic the herbicide contains. MSMA is currently labeled for use on golf course turf, sod farms, etc. It is not a “restricted use” herbicide and can be purchased by a lay person, no license required. You can Google and read up on it, just remember, “the label is the law (federal)”.

A better option would be the herbicide quinchlorac which will kill crabgrass but safe to use on Bermudagrass. Never personally used it as I don’t have a Bermudagrass grass lawn but others on this board have and hopefully will comment.

I have used Quinclorac in my Bermuda grass. I've used it successfully on crabgrass and barnyard grass. Expect some yellowing of the Bermuda but it will bounce back.