Sublethal effects of buprofezin on development, reproduction, and chitin synthase 1 gene (SfCHS1) expression in the white-backed planthopper, Sogatella furcifera (Hemiptera: Delphacidae)

The white-backed planthopper, Sogatella furcifera (Horvath) (Hemiptera: Delphacidae), is a major rice pest in some Asia-Pacific countries. Buprofezin is an insect growth regulator with relatively low mammalian toxicity but high efficacy to many rice pests. In this study, we estimated the toxicity of buprofezin against 3rd-instar nymphs of S. furcifera using the rice-stem dipping method. The results showed that the LC50 of buprofezin to 3rd-instar nymphs were 0.89 mg/L. When 3rd-instar nymphs were exposed to the LC10 and LC25 (0.10 and 0.28 mg/L) of buprofezin, the duration of juvenile development was significantly prolonged in the F-0 and F-1 generations. The fecundity (eggs per female) of the F-1 females was reduced by 5.29% and 12.34%, respectively, in addition to the survival rate, emergence rate, copulation rate, and hatchability were decreased by treatment with buprofezin at LC10 and LC25, compared with the control group. The relative fitness of S. furcifera in LCis and LC25 treatments was reduced by 47% and 63%, respectively. Furthermore, real-time quantitative PCR analyses revealed increased the expressions of SfCHS1 and its two variants following the exposure of nymphs to buprofezin. Increased these genes mRNA levels associated with reduced chitin biosynthesis may result from the inhibition of chitin synthase activity, and thereby leading to a higher mortality of S. furcifera. Overall, sublethal concentrations of buprofezin suppressed the population growth of S. furcifera.