Two-spotted spider mites, Tetranychus urticae Koch have been a problem for many years. A broad approach to population management is needed. Hybridization between greenhouse strains of T. urticae and introduced strains may result in a strain with different life-history traits. Life-history traits of mites in greenhouses should be regularly monitored to provide an historical data base, and input for simulation models. Phytoseiulus persimilis Athias-Henriot operates well within certain ecological limits. A predator community approach may be useful when conditions are not suitable for P. persimilis. After 30 years of mass rearing, the development rate of P. persimilis has not changed, but fecundity appears to be reduced, largely as a result of reduced reproductive period. Insectaries have attempted to set quality standards, but many factors can affect P. persimilis and tests must be developed for rapid assessment of quality at the greenhouse. More work is needed to develop and implement rapid sampling protocols with acceptable precision and accuracy. Digital data acquisition and management systems will be necessary, to summarize data spatially and temporally, provide input for simulation models, and provide a data base for research analyses. Simple simulation models, although inaccurate, may be useful in answering specific pest management questions.