Sublethal effects of Oberon Speed® on Phytoseiulus persimilis and Amblyseius swirskii (Acari: Phytoseiiidae) and potential compatibility for integrated management of two-spotted spider mite

The two-spotted spider mite, Tetranychus urticae Koch (TSSM), is an important cosmopolitan pest of horticultural crops that is often managed in greenhouses with a combination of acaricides and augmentation of predatory mites. Here we examined the transgenerational effects of low concentrations of a widely-used acaricide, Oberon Speed® (a combination of spiromesifen and abamactin), on the life history of TSSM and two of its predators, Phytoseiulus persimilis Athias-Henriot and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). The concentrations employed corresponded to the LC10, LC20 and LC30 values calculated for TSSM protonymphs 48 h post-exposure in a topical bioassay, which yielded an LC50 value of 207.2 ppm. Parental exposure of TSSM to all three sublethal concentrations increased the total developmental time of progeny; both the LC20 and LC30 treatments reduced adult longevity and number of oviposition days, but only the LC30 treatment increased the preoviposition period. Similarly, both the LC20 and LC30 treatments significantly reduced life table parameters (r, R0, λ, and GRR), and increased generation time (T) and population doubling time (DT). Although maternal exposure to the acaricide had various impacts on progeny life history, the life table parameters of A. swirskii were largely unaffected in comparison to those of P. persimilis, suggesting the former species would be more compatible for integration with Oberon Speed® for control of TSSM in greenhouse vegetable production.