Razi University

   The two-spotted spider mite,  Tetranychus urticae  (Koch), is one of the most important and damaging phytophagous mites in fields and greenhouses, and its control is of great importance due to its wide host range. Its short life cycle, high reproductive rate, and detoxification ability have led to the rapid development of resistance to pesticides. Therefore, integrating biological control methods with compatible acaricides to reduce pesticide use and environmental risks is a primary goal of Integrated Pest Management (IPM) programs. Functional response is one of the most critical predator-prey interactions for predicting the ability and determining the efficiency of natural enemies in reducing pest populations below the economic injury level. In this study, the functional response and life table parameters of the predatory mite  Amblyseius swirskii  and  Neoseiulus californicus  were investigated on protonymphs of  T. urticae  using strawberry leaf discs (Fragaria  ×  ananassa  cv. Paros) under laboratory conditions. Functional response experiments were conducted at prey densities of 2, 4, 8, 16, 32, 64, and 128 individuals, along with treatments of LC25 concentrations of two acaricides, Bromopropylate and GC-Mite, applied to the predatory mites. Acute toxicity bioassay results showed that both acaricides had satisfactory efficacy against the pest, but GC-Mite exhibited higher toxicity against  T. urticae  (LC50 = 275.06 ppm). Both predatory mites showed higher tolerance to the acaricides compared to the prey, with  A. swirskii  demonstrating greater tolerance tha  N. californicus  under acaricide treatments. Based on logistic regression results, the functional response in all treatments (control and acaricide treatments) was type II. Fitting the data to Rogers' model revealed that acaricides at LC25 concentration significantly altered functional response parameters. The shortest handling time (Th) and highest daily predation rate (T/Th) were recorded in the GC-Mite treatment o  N. californicus  (0.014 day and 68.96 prey per day, respectively). In contrast,  A. swirskii  had the highest initial attack rate in the control treatment but experienced a sharp decline in attack rate under GC-Mite treatment. Life table results also indicated that exposure to low concentrations of acaricides had significant negative effects on the biological characteristics of the mites, particularly  N. californicus, such that total longevity, oviposition period, total fecundity (which decreased by approximately 40%), and the intrinsic rate of increase (r) were reduced under both acaricides. Meanwhile,  A. swirskii  howed greater compatibility and stability in demographic parameters against these compounds. Overall, the results from both life table and functional response sections demonstrated that although low concentrations of Bromopropylate and GC-Mite have inhibitory effects on the demographic characteristics of predatory mites, especially  N. californicus, they did not significantly impair their predation potential and in some cases even increased the predation rate. Based on the findings of this study, the greater compatibility of  A. swirskii  when exposed to both acaricides and the increased predation rate of  N. californicus