Lambda-cyhalothrin and bifenthrin from pyrethroids have been used for many years to control the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), which causes serious economic damage in many cultivated and ornamental plants worldwide. In this study, resistant populations previously selected in the laboratory with lambda cyhalothrin and bifenthrin (LR and BR, respectively) were compared with the susceptible strain GSS to assess the effect of the resistance on fitness. Life tables were created by using some biological parameters such as development time, fecundity and adult longevity. Data analysis revealed that lambda-cyhalothrin and bifenthrin resistant populations of T. urticae had no fitness disadvantages. The relative fitness values of the LR (1.09) and BR (1.19) populations also showed an advantage over the susceptible population. Total development and generation time were prolonged in both resistant populations. In the LR population, the life span of the adult females was prolonged, whereas the rm value was found to increase in the BR population. Total fecundity and egg hatchability were also found to be higher in both resistant populations than the susceptible strain GSS. The net reproduction rate (R0), one of the life table parameters, was significantly increased in the LR and BR populations. In this study, lambda-cyhalothrin and bifenthrin resistance affected some biological parameters in T.urticae, but the resistance did not produce a loss of fitness in the LR and BR populations. These findings have significant implications for resistance management strategies in terms of the state and management of resistance.
Systematic and Applied Acarology
Vol. 27 • No. 3
Vol. 27 • No. 3