Effect of fipronil on the reproduction, feeding, and relative fitness of brown planthopper, Nilaparvata lugens

Applications of fipronil (1.25 x 10(-2) mu g) and fipronil (7.50 x 10(-3) mu g) significantly stimulated the fecundity of Nilaparvata lugens compared with the control. The stimulating effect of fipronil on fecundity was dose-dependent. Fifteen and 30 days after treatment, the quantity of honeydew significantly increased in 1.25 x 10(-2) mu g fipronil treatment. Fifteen days after treatment, the effect of fipronil on the quantity of honeydew was dose-dependent. The results revealed that the fipronil treatment group had developmental advantages. Selection with 25 mg/l fipronil led to a continuous increase in the resistance ratio (from 1.0 to 30.05) in eight generations. The life table indicated that the resistant strain had obvious disadvantages, including decreasing the survival rate from 3rd to 5th instar in G8 generation and decreasing fecundity in G5 generation. Compared with the susceptible strain, resistant insects had a relative fitness of only 0.577 and 0.750. The lower fitness includes a lower larval survival rate from 3rd to 5th instar (in G8 generation), lower adult emergence rate (in G8 generation), lower copulation rate (in G8 generation), lower fecundity (in G5 generation) and fewer offspring. It was concluded that the brown planthopper had the potential to develop high resistance to fipronil but that the lower fitness of resistant hoppers could result in quick recovery of sensitivity when the population did not come into contact with fipronil. This means that a reasonable resistance management program with less fipronil use may efficiently delay or even stop resistance development.