Effects of sublethal concentrations and application concentration of SYP-9625 on Tetranychus cinnabarinus (Boisduval) and its natural enemy, Neoseiulus californicus (McGregor)

Objective Exploring the effects of acaricides on predatory mites is crucial for the combination of biological and chemical control of pests. In this study, sublethal effects of the new acaricide SYP-9625 on Tetranychus cinnabarinus (Boisduval), effects of application concentration of SYP-9625 on the predatory mite Neoseiulus californicus (McGregor) and functional responses of N. californicus were assessed. The aim of the present study was to evaluate and explore the application of new acaricide SYP-9625 with natural enemy N. californicus . Method All the experiments were under laboratory conditions [25 ± 1 °C, 16:8 (L:D) h and 75 ± 5% RH] and based on an age-stage, two-sex life table. The sublethal concentrations against T. cinnabarinus , including LC 10 (0.375 μg/mL) and LC 30 (0.841 μg/mL) and the application concentration (100 μg/mL) of SYP-9625, were used to evaluate effects on population parameters of N. californicus . Result T. cinnabarinus females treated with LC 30 exhibited significantly reduced net reproductive rates ( R 0 =11.02) of offspring compared to females treated with LC 10 ( R 0 =14.96) and untreated females ( >R 0 =32.74). However, the intrinsic rate of increase ( r m ) and finite rate of increase ( λ ) of N. californicus indicated that the application concentration of SYP-9625 had no significant negative effect on treated N. californicus eggs ( r m =0.277, λ =1.319) compared to the control ( r m =0.292, λ =1.338). Additionally, the sublethal concentrations against T. cinnabarinus including LC 10 and LC 30 showed a dose-dependent mechanism on the predatory mite. SYP-9625 also stimulated the predatory capacity of N. californicus against immobile stages such as eggs and larvae. Conclusion It is demonstrated that sublethal concentrations of SYP-9625 can inhibit population growth of T. cinnabarinus . And the sublethal concentrations and application concentration had little effect on the population growth of N. californicus . The two advantages showed great commercial potential of this new acaricide. Therefore, N. californicus can manage T. cinnabarinus populations effectively with appropriate SYP-9625 concentrations.