I found the following information interesting:

Natural Tick Sprays and Powders

If your tick infestation is particularly severe, or you live in an area with a Lyme disease problem, cultural controls and other preventative methods aren’t enough. You can apply natural tick control agents to your lawn and garden, especially near shrubby areas that require regular weeding.

You can use a natural insecticide composed of a blend of nontoxic but effective plant oils, including oil of wintergreen, rosemary oil, and peppermint oil. Although these essential oils are nontoxic, they can still cause skin and eye irritation, so follow manufacturer’s application and dilution directions.

Many organic gardeners are familiar with the use of beneficial nematodes to kill garden pests like grubs, but you may not realize that some parasitic nematodes target ticks. It’s satisfying to imagine these microscopic helpers feeding on the carcasses of ticks throughout the yard. Look for the nematode S. feltiae, which is commercially available and can infect as many as 100% of the ticks it meets.

Read more: http://organicgardens.suite101.com/article.cfm/get_rid_of_ticks#ixzz0PxozycRB