Biological control of Tetranychus urticae mite by predatory mites compared to pesticides on strawberry plants under field conditions

Background: The two-spotted spider mite, Tetranychus urticae (T. urticae) is one of the most serious pests affecting strawberry plants. The use of various chemical pesticides has posed numerous environmental risks, necessitating the search for alternative solutions that are safer and more sustainable, such as the use of biological control agents, which offer an effective and environmentally friendly method in pest management. Methods: This study was conducted to compare the biological control of the two-spotted spider mite by releasing predatory mites three times over two successive seasons, comparing to three pesticide systems applied by two methods as well as, to estimate the impact of the release processes and applied pesticides on strawberry yield. Results: The predatory mites: Phytoseiulus persimilis (P. persimilis), and Neoseiulus californicus (N. californicus), demonstrated significant efficacy in reducing populations of T. urticae on strawberry plants during 2023 and 2024 seasons. P. persimilis outperformed the other species, recording the lowest numbers of eggs and motile stages of the pest, with reduction rates of 81.7% and 84.9% in the 2023 season, and 72.6% and 76.6% in the 2024 season. N. californicus ranked second in effectiveness, with reduction rates of 78.4% and 74.6% in the 2023 season, and 68.9% and 70.4% in the 2024 season. The chemical treatment of (thiamethoxam, micronized sulfur, and mineral oil) also showed good efficacy, particularly when applied as a foliar spray, with reduction rates of 85.7% and 81.5% in the 2023 season, and 68.1% and 71.4% in the 2024 season. Regarding strawberry yield, the biological treatment with P. persimilis achieved the highest increase in yield, with 38.7% in the 2023 season and 39.7% in the 2024 season. Among the chemical treatments, the foliar spray of thiamethoxam, micronized sulfur, and mineral oil resulted in the highest yield increase, with 46.2% in the 2023 season and 44% in the 2024 season. Conclusions: It could be recommend the use of P. persimilis and N. californicus predators along with the treatment of (thiamethoxam-micronized sulfur-mineral oil) to control T. urticae infestation on strawberry plants under field conditions.