Strict regulations limiting the availability of synthetic pesticides on vegetable crops in greenhouses have created a new challenge for plant protection. Many pests such as whiteflies, thrips aphids, spider mites, and other, still remain dangerous and difficult to control on vegetable crops in greenhouses. In the experience of many and in a review of world literature, it has been noted that effective methods of biological control of many pests are already available, or can be easily adapted for practice. According to the Polish Directives, biological methods should be used prior to any application of chemical products. Thus, biological control is a priority in plant protection, especially for vegetable crops in greenhouses. Tetranychus urticae is the most important pest in greenhouse crops. Successful control of this pest is very difficult. In laboratory studies the predator mites Amblyseius swirskii and Phytoseiulus persimilis showed a high efficacy when used together to control of two-spotted spider mites (86% mortality). When predators were used separately they were less effective against the pest (about 63% mortality). The studies showed that A. swirskii was competitive with P. persimilis populations for controlling the two-spotted spider mite. Other predators mites: Amblyseius degenerans and Amblyseius californicus used in the experiments demonstrated neutral interaction.