We use cedar oil. It does not kill them, but it repels them. And it works!!!! Many of the chemicals that kill ticks also kill bees and butterflies. But not cedar oil. You can even harvest from the garden the same day you spray. This year I used
cedarcide because it was cheaper and they through in the dispenser. I only spray around the perimeter of an acre of land. Cost me about $30 a year.
Wondercide is also a good cedar oil source. I live in New England and ticks are horrible this year. But I have only seen three so far.