We compared the application of IC2, a minimal-risk (25B) botanical compound containing 10% rosemary oil, with bifenthrin, a commonly used synthetic compound, and with water for the control of Ixodes scapularis Say ( = Ixodes dammini Spielman, Clifford, Piesman & Corwin), on tick-infested grids in Maine, in an area where Lyme disease is established and other tick-borne diseases are emerging. High-pressure sprays of IC2, bifenthrin, and water were applied during the peak nymphal (July) and adult (October) seasons of the vector tick. No ticks could be dragged on the IC2 grids within 2 wk of the July spray, and few adult ticks were found in October or the following April. Similarly, no adult ticks could be dragged 1.5 wk after the October IC2 spray, and few the following April. No ticks were found on the bifenthrin grids after either spray through the following April, whereas substantial numbers of ticks remained throughout on the grids sprayed with water. Thus, IC2 appears to be an effective, minimum-risk acaricide to control the vector tick of Lyme disease.