Effects of sub-lethal concentrations of Biomite® on life-history traits of Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the key pests that can damage a wide range of crops in farms and greenhouses. Using chemical pesticides is one of the main methods for its management. Laboratory bioassays were conducted to evaluate the effects of sub-lethal concentrations (LC5, LC10 and LC20) of Biomite (a formulation based on Citronellol) on biological characters and life table parameters of T. urticae under laboratory conditions (25±2°C, 60±5% RH, and L:D16:8 hours). Data were analyzed based on age-stage, two-sex life table analysis. Our results indicated that when adults of T. urticae were treated with LC5, LC10 and LC20 of Biomite, the oviposition period and total lifetime were significantly reduced compared with the control. The highest and lowest values of the fecundity (61.1 and 41.56 eggs/female) and longevity (13.01and 9.97 days) were obtained in control and LC20, respectively. The individuals treated with LC10 (R0 = 38.1) and LC20 (R0 = 32.92) showed a significantly reduced net reproductive rate, compared to individuals that treated with LC5 (R0 = 47.01) and to the control (R0 = 48.88 individuals/female/generation). The intrinsic rate of increase (r) and finite rate of increase (λ), were not significantly reduced in different treatments compared to the control. The mean generation time (T) decreased significantly at upper concentration (LC20=15.58 days), in comparison to LC5 (16.66 days). Due to the obtained results of current study and considering the detrimental effects of Biomite on some biological parameters, it could be incorporated in IPM programs of T. urticae.