Sublethal effects of chlorfenapyr and acequinocyl on the functional and numerical responses of the predatory mites Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) feeding on Tetranychus urticae (Acari: Tetranychidae).

Abstract

Tetranychus urticae Koch, commonly known as two spotted spider mites, is a major agricultural pest that causes significant economic loss. Predatory mites, such as Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor) are important biological control agents for this pest. However, the efficacy of these predators can be compromised by pesticide application. This study investigated the impact of two acaricides, chlorfenapyr and acequinocyl, on the functional and numerical responses of P. persimilis and N. californicus feeding on T. urticae. Bioassay tests were conducted using a leaf disk dipping method at various pesticides concentrations. Chlorfenapyr exhibited approximately five times higher toxicity than acequinocyl for both predatory mite species and N. californicus exhibited higher tolerance to both acaricides compared to P. persimilis. Functional response experiments assessed the predation rates of 10-day-old predatory mites on different densities of T. urticae nymphs. Analysis of functional response data indicated a Type II response across all treatments. The sublethal concentrations of both acaricides negatively affected the predatory efficiency of both species by reducing attack rate and daily prey consumption and increasing handling times. The numerical response data showed a reduction in egg production correlating with increased pesticide concentrations. Additionally, the efficiency of conversion of ingested food (ECI) decreased with increasing pesticide concentrations. These findings highlight the detrimental effects of pesticides on beneficial arthropods and emphasize the need for integrated pest management strategies that minimize the reliance on chemical control.