The Study on Fecundity Life Table Parameters of Abamectin-Resistant and -Susceptible Populations of Tetranychus urticae Koch (Acari: Tetranychidae)

The impairment of the reproductive performance of pesticide resistant individuals in pesticide-free environment is the result of fitness costs associated with pesticide resistance, which is often determined by resource allocation from a basic physiological process to the protection against pesticides, favoring survival at the expense of reproduction. In this study, the fecundity life table parameters of abamectin-resistant and susceptible populations of Tetranychus urticae Koch were studied under laboratory conditions at 24±2˚C, 70±10 R.H. and 16:8 (L: D). In all experiments, reproductive fitness parameters were measured for each population on the Vigna ungiculata (L.) leaves. Standard error of life table parameters was calculated using the Jackknife method. Results showed that susceptible population exhibited significantly higher intrinsic rate of natural increase (r_m), finite rate of increase (λ) and net reproductive rate (R₀) than resistant population. No significant difference occurred in mean generation time (T) between the susceptible and resistant populations, but doubling time (DT) of resistant population was higher than that in susceptible one. Results of present study suggest that the resistant population may be less fit than susceptible compartment.­