The effect of the combination of diatomaceous earths and Phytoseiulus persimilis on the biological control of Tetranychus urticae under laboratory conditions

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The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is one of the key pests causing important economic losses in crops. From the predatory mites, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) is used effectively in the biological control of pest mites. On the other hand, diatomaceous earths has a significant potential for controlling numerous arthropod pests including pest mites. Synergistic interactions of different biological control agents such as predatory mites and diatomaceous earths can provide significant benefits in more effective biological control of pest mites. This laboratory study investigated the effect of combined and separate application of the predatory mite, P. persimilis and diatomaceous earth in the biological control of T. urticae. This research is the first to demonstrate the synergistic effect of diatomaceous earths on the efficacy of P. persimilis. After 96 hours, the highest mortality, with 73.19±0.72%, was observed in the combined treatments of P. persimilis and diatomaceous earths. Moreover, significant differences were observed in the fecundity of T. urticae among the test groups. The lowest mean number of eggs per T. urticae female was found in the combined treatment. Simultaneous application of P. persimilis and diatomaceous earths thus turned out to be the most effective treatment against T. urticae. Our laboratory results thus suggest that diatomaceous earth has the potential to enhance the biological control of T. urticae by P. persimilis. Future studies should verify whether these effects translate to greenhouse and field conditions.