how to destroy crabgrass from your lawn?

Answer 1

Go to your local mega supply house and get a weed and feed product and apply by the directions.

Answer 2

Believe it or not, but napalm kills crabgrass while leaving other species of grass alone (unless you light it on fire).

I'll leave it up to you to figure out how to make some at home.

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...The discovery was something of a coup for Fieser. His research team at Harvard beat chemists from Du Pont and Standard Oil in a Government competition to develop napalm. In the course of his research, Fieser found a perfectly good civilian use for the product: it made a fine crabgrass killer, burning away its seeds while leaving good grass roots untouched. During and after World War II, he received several letters of thanks for his invention, which soldiers claimed saves thousands of American lives in battle. No one ever complained to him about the use of napalm until Viet Nam....

Answer 3

Weedkiller.