How can I kill ants in my grass?
There are hundreds of different species of black ants in the US, and for the most part they provide a valuable resource for your grass. Their natural behavior aerates a lawn and distributes recycled organic material to nourish your grass. If you are bothered by unsightly anthills, they can be raked away or doused with boiling water to improve the lawn's appearance. Treating areas of ant concentration with a solution of borax and sugar should be done with caution; the mixture is poisonous to ants but to pets and humans as well.
Fire ants, on the other hand, are a nuisance worth addressing. These copper or red ants are fast and sting painfully. The Organic Lawn Care Manual by Paul Tukey recommends the botanical solution spinosad to address fire ants. A nerve toxin to the insects, spinosad can be broadcast on the lawn or applied locally to ant hills. It acts as a bait and is most effective when ants are actively seeking food at temperatures above 65 degrees F. but not in high heat which will disarm the toxic properties of the treatment.
Courtesy of NYBG Plant Information Service