Sevin (Carbaryl) is good for small areas but gets expensive when you talk of acerage. As pdq notes, it is often sold with malathion, a good all-round insecticide. Sulfur (powdered) is good but may not be practical for you.
This little article from the U. S. Army Center has good ideas for control based on vegetation control. So many plants and shrubs that we like can harbor ticks that this method is poor for landscaped and planted areas.
http://www.smdc.army.mil/2008/Safety/Articles/TickControlAroundTheHome.pdf

For large areas, talk to a pest control agency, but remember, birds and animals are always bringing in more.