Fitness cost of nitenpyram resistance in the brown planthopper Nilaparvata lugens

A resistant strain of Nilaparvata lugens has been continuously selected in the presence of nitenpyram for 27 generations under laboratory conditions in order to study the fitness cost of nitenpyram resistance. The resistance to nitenpyram in N. lugens was at a high level (resistance ratio = 144.7-fold). Life-tables of the nitenpyram-resistant strain and the susceptible strain (SS) of N. lugens were studied by using the age-stage, two-sex life-table approach. Compared to the SS, the relative fitness of the resistant strain of N. lugens was 0.55, with a lower intrinsic rate of increase (r) and net reproductive rate (R (0)). Changes in some life-history traits of the resistant strain were also observed. The duration of the egg stage, the development times of the first-, third- and fourth-instar nymphs, the adult preoviposition period and the total preoviposition period of the resistant strain were significantly increased, whereas the longevity, egg survival rate and fecundity (eggs/female) (absolute fitness) were significantly decreased in the resistant strain of N. lugens. The lower intrinsic rate of increase (r) and net reproductive rate (R (0)) seemed to be largely due to number of eggs laid, developmental time and egg survival rate. These results showed that the development of nitenpyram resistance may lead to significant fitness costs in resistant populations of N. lugens. This study provided valuable information for facilitating the development of nitenpyram-resistance management strategies.