The best defence against ticks is to keep vegetation cut back as low as possible. Ticks crawl up vegetation and wait for a host animal to brush against it. If you eliminate tall vegetation the ticks will have a difficult time finding a host. The second most important source of ticks is pets. Be sure outdoor pets are treated with a "flea&tick" medication labelled for ticks, not all flea meds work on ticks so check the label carefully. Also, flea collars work well for ticks but, ironically, not so well against fleas.