The twospotted spider mite, Tetranychus urticae Koch, is a serious pest of greenhouse-grown ornamental crops. Possible control options for this pest include chemical and biological strategies. Floramite® is a newer “reduced-risk” miticide which is highly effective but expensive relative to traditional pesticides. Biological control with the predator Phytoseiulus persimilis (Athias-Henriot) is an effective but under-used option for managing TSM. Previously, experiments by our group in research greenhouses have evaluated the effectiveness of three different control strategies for twospotted spider mite on ivy geranium and impatiens: 1) a single Floramite application, 2) a single release of P. persimilis based on TSM density that is estimated by sampling, and 3) a weekly release of P. persimilis based on crop area at rates recommended by the commercial supplier of the predators. Results showed that Floramite and sampling-based predator releases are capable of effective and timely control of twospotted spider mite at various initial pest densities, while area-based predator releases produced variable results and unacceptable levels of plant damage. However, to advise growers, the effectiveness and costs of these strategies needed to be evaluated on a larger scale and under actual commercial growing conditions with regards to temperature, irrigation, and methods for efficiently distributing predators. Therefore, we (1) tested the relative and absolute effectiveness of each strategy in a commercial operation, and (2) conducted an economic analysis to compare the costs of the chemical and biological strategies.