There are no selective herbicides to take quackgrass out of a bluegrass lawn. You can use a nonselective herbicide to kill quackgrass and any nearby bluegrass. Digging is not generally sufficient because of the vigorous quackgrass rhizomes. If you have a situation where you can grow your bluegrass under normal water in spring, shut off the water to allow your bluegrass to go completely dormant in summer, and spray the still-green quackgrass with a nonselective herbicide. That way, you can take out the quackgrass without harming the bluegrass. This isn't appropriate in many situations based on traffic to the lawn, unsightly appearance, or other concerns, but it can be effective.

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