The common spider mite Tetranychus urticae Koch is a dangerous pest. This pest occurs more frequently on cucumber crops than other pests and damages more than 200 other plant species, including aubergine, pepper, tomato, lemon, chrysanthemum, rose and carnation. The specific conditions of the protected environment allow greater use of biological agents for pest control. The modern concept of natural plant protection involves a combination of several birth control agents used to suppress pest populations. In this study, the authors studied the effect of biological preparations on the survival of the predatory mite Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) under laboratory conditions. A laboratory evaluation was made of the effect of the biological preparations Bitoxybacillin, 1% and Fytoverm, 0.2%. These preparations significantly reduce acariphage numbers when released immediately after treatment. The predatory mite showed higher sensitivity in the variant with Fitoverm, 0.2%. Acariphage numbers decreased, but not significantly when plants were treated with Biovert (1%) and the fungus strain Metarhizium robertsii. Thus, plant treatment and acariphage release should be carefully regulated when phytoseiulus is released because of the adverse effects of bio preparations. The results confirm the potential use of biological practices combined with the predatory mite Phytoseiulus persimilis against the common spider mite Tetranychus urticae.