Biological and population growth parameters of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) on cucumber: effect of different vermicompost: soil ratios

Two-spotted spider mite, Tetranychus urticae Koch, is one of the important pests of cucumber, which can cause severe damage on it. Vermicompost is one of the organic fertilizers, as its addition to the soil can decrease the population of the pest. In this research, effect of four different vermicompost: soil ratios including 0:100 (control), 10:90, 20:80 and 30:70 % was investigated on biological and population growth parameters of T. urticae. The experiments were carried out in Petri dishes in a growth chamber at 25 ± 2 °C, 65 ± 5 % RH and 16 L: 8 D. The duration of developmental stage, was significantly affected by vermicompost ratios. The longest immature period, shortest longevity of females and shortest oviposition period were obtained at 30:70 % ratio. Furthermore, vermicompost ratios significantly affected population growth parameters of the mite. The intrinsic rate of natural increase (rm) of the mite ranged from 0.216 to 0.247 day-1, which its lowest and highest values were at 30:70 % ratio and control plants, respectively. The lowest net reproductive rate (R0) and finite rate of increase (λ) of the mite and the highest value of mean generation time (T) and doubling time (DT) were estimated at 30:70 % ratio. The results of this study showed that 30:70 % ratio had better potential for decreasing the population of the two-spotted spider mite and it can be used in the mite IPM programs.