I am using Compare-N-Save Concentrate Grass and Weed Killer, pruchased from amazon. I have read about a recipe to prevent insects on another forum . It was the mixture of table salt, white vinegar and dish wash. you can try this as well.
I heard about the mixture of white vinegar, salt, and dish soap. I use compare-N-save. But if you don't like to use weed killers you can try this recipe