Sublethal deltamethrin induces transgenerational fitness costs in Neoseiulus agrestis (Karg) (Acari: Phytoseiidae): impaired parental reproduction and offspring development.

The predatory mite, Neoseiulus agrestis (formerly known as Neoseiulus striatus until its revision in 2022), is considered a promising candidate for biological control of small sucking pests, particularly Tetranychid mites. However, in integrated pest management (IPM) programs, understanding the influences of chemical pesticide applications on predatory mites is of great significance. In this study, the toxicity of ten pesticides on adult female N. agrestis was evaluated under laboratory conditions to determine their LC₂₀, LC₅₀, and LC₉₀ concentrations using the slide impregnation method. Among these pesticides, deltamethrin, which exhibited the highest toxicity, was selected for further investigation into its effects on the fitness of the next generation of N. agrestis preying on Tetranychus urticae Koch. The relative toxicity of the ten tested compounds, ranked from highest to lowest was as follows: deltamethrin, bifenthrin, endosulfan, methomyl, omethoate, imidacloprid, emamectin benzoate, carbosulfan, spinosad, and abamectin. Notably, deltamethrin exhibited the highest toxicity against N. agrestis, with a median lethal concentration (LC₅₀) of 0.020 mg/L. Exposure to sublethal and LC₅₀ deltamethrin doses significantly impacted the adult lifespan and reproductive capacity of treated predators. Predators exposed to LC₂₀ concentrations exhibited markedly shorter offspring development time and lower fertility rates. The sublethal deltamethrin dose induced marked alterations in the life table parameters of N. agrestis. These findings suggested that deltamethrin adversely affected both the developmental duration and life table parameters of the next generation of N. agrestis. To better understand predator-insecticide dynamics in the presence of biotic and abiotic stresses in the field, future studies could further evaluate this aspect under field and semi-field conditions.