Time-dependent mortality and reduced population growth potential in Tetranychus urticae (Acari: Tetranychidae) following exposure to graphene oxide-treated leaves

Graphene oxide (GO) is increasingly investigated for crop protection, but its direct effects on the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), remain poorly defined. Because short-term mortality alone may not reveal effects on population performance, we combined an acute leaf-dip bioassay with age-stage, two-sex life-table analysis under laboratory conditions. Adult females were exposed to kidney bean leaves treated with GO suspensions at nominal concentrations of 0.05 to 0.80 mg/mL. Mortality increased with concentration and exposure time, reaching 22.2% after 24 h and 87.8% after 48 h at 0.80 mg/mL, while control mortality remained 1.1%. The 24-h response did not reach 50% mortality within the tested range; the model-estimated 48-h LC10, LC50, and LC90 values were 0.15, 0.46, and 0.91 mg/mL, respectively, with LC90 extrapolated beyond the highest tested concentration. A 0.10 mg/mL GO suspension, selected from the adult acute-response data, was subsequently evaluated under continuous life-cycle exposure. Preadult survival remained high in both treatments, but GO-treated leaves reduced adult female longevity from 30.0 to 23.6 d and fecundity from 81.6 to 65.1 eggs per female. Net reproductive rate, intrinsic rate of increase, and finite rate of increase declined from 56.6 to 38.6 offspring per individual, 0.141 to 0.127 d−1, and 1.152 to 1.135 d−1, respectively. These findings show time-dependent adult mortality and reduced reproductive and population growth potential under laboratory conditions, supporting further evaluation of GO-treated leaves under crop-based conditions and with relevant non-target organisms.