Sublethal Effects Of Indoxacarb And Chlorantraniliprole To Nilaparvata Lugens (Stal)(Hemiptera:Delphacidae)

The brown planthopper, Nilaparvata lugens (Stal)(Hemiptera:Delphacidae), is a classic example of a pest that experiences insecticide-induced fecundity. The insecticides indoxacarb and chlorantraniliprole were recently developed with high insecticidal activity in the control of rice yellow stem borer, Tryporyza incertulas (walker) and rice leaffolder, Cnaphalocrocis medinalis (Giienee). We examined the changes in the fecundity of N. lugens, the vitellogenin (Nlvg) gene expression and the vitellin contents of adult females exposed to these insecticides. And we also investigated the total protein, RNA, and DNA, juvenile hormone (JH) III contents in the ovaries and fat bodies of N. lugens adult females after treatment with the insecticide indoxacarb. The results showed as follows:1. Suppression of fecundity, Nlvg gene expression and vitellin contents in Nilaparvata lugens Stal (Hemiptera:Delphacidae) adult females exposed to indoxacarb and chlorantraniliproleIndoxacarb and chlorantraniliprole significantly suppressed the fecundity of the females and the expression of Nlvg mRNA. Treatments with10,20,40and80mg/L indoxacarb decreased Nlvg mRNA expression by35.4%,74.4%,79.6%and61.9%, respectively, and treatments with7.5,15,30,60and80mg/L chlorantraniliprole decreased Nlvg mRNA expression by79.3%,40.2%,40.0%,79.8%and51.8%, respectively. The vitellin contents in both the ovaries and fat bodies of the adult females also decreased, indicating that the two insecticides suppressed the synthesis of vitellin in the fat bodies and the transfer of vitellin to the ovaries. This decrease in the vitellin contents of the ovaries may be attributed to the low Nlvg expression, as there was a negative correlation between the vitellin contents and the expression level of this gene, indicating that these insecticides influenced the fecundity of N. lugens by affecting the expression of Nlvg mRNA. The study of the effects of indoxacarb and chlorantraniliprole on fecundity should have significance for the wide usage in rice plants.2. Effects of indoxacarb on total protein, RNA, and DNA contents in the ovaries and fat bodies of Nilaparvata lugens Stal (Hemiptera:Delphacidae) adult females All of the tested concentrations of indoxacarb caused a significant decrease in the protein and RNA contents in the ovaries and fat bodies of the adult females that developed from nymphs fed indoxacarb-treated rice plants compared with those from nymphs fed untreated rice plants, while the DNA contents did not significantly decrease except at5days among all of the tested days after emergence. In general, the protein and RNA contents in both the ovaries and the fat bodies decreased linearly with the concentrationsof indoxacarb. There was a significant negative correlation between the total protein and RNA contents and the concentrations of indoxacarb, showing that the total protein and RNA were more sensitive to indoxacarb than was the DNA, and that the changes in RNA contents in turn influence protein synthesis in both the ovaries and fat bodies. The RNA-to-protein ratios in both the ovaries and fat bodies were consistently0.20in all of the treatment groups and in the control groups.3. Sublethal effects of indoxacarb on juvenile hormone of Nilaparvata lugens Stal (Hemiptera:Delphacidae) adult femalesAll of the tested concentrations of indoxacarb caused a significant decrease in JH III titer of N. lugens adult females both before and after mating, and JH III titer decreased with the increasing of insecticide concentration. There was a significant negative correlation between JH III titer and the concentrations of indoxacarb. JH III titer decreased by32.2%,31.7%and44.5%at1,3,5days before mating compared with the untreated controls, and42.8%,52.3%and46.4%at1,3,5days after mating, respectively after indoxacarb treatments. JH III titer in N. lugens adult females after mating was higher than those of before mating. The present findings provide valuable information for improving our understanding of the physiology and biochemistry mechanisms of fecundity in N. lugens induced by indoxacarb and also provide us with theoretical foundation to the reasonable use of indoxacarb in rice plants.