can include using: cedar oil, neem, Apple Cider Vinegar(organic with the "mother"), grapefruit peels.
this has been very successful for us. You may need to use it more or less, or use more lemon, etc. to find the exact mixture that works for you.
I currently have 3 40-45 pound dogs that like to spend alot of time outside. One batch lasts us about a month.