Strategies for controlling invasive species can be aimed at any or all of the stages in the life cycle. In this paper we show how to combine biological data on population dynamics with simple economic data on control cost options to determine the least costly set of strategies that will halt an invasion. We then apply our methods to oyster drills (Ocinebrellus inornatus), an economically important aquaculture pest that has been accidentally introduced worldwide. If the costs of intervention were the same across life stages, extermination of adults would be an inefficient way to control species with the population dynamics characteristics of invaders. In the oyster drill case, however, efficient control targets adults because they are much easier to find.