Heat-Dependent Fecundity Enhancement Observed inNilaparvata lugens(Hemiptera: Delphacidae) After Treatment With Triazophos

The brown planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) is a serious pest of rice crops in the temperate and tropical regions of Asia and Australia, and it is also a classic example of an insecticide-induced resurgent pest. Brown planthopper outbreaks have been reported to be closely associated with pesticide application. Previous studies have shown that the insecticide triazophos enhances thermal tolerance and fecundity in brown planthopper. However, the effects of triazophos and high temperature on reproductive capacity have not been studied in high temperature-conditioned reciprocal pairs of adult males and females. The present experiments showed that triazophos enhanced the reproductive capacity of brown planthopper under high temperature (34°C). The number of eggs laid by females treated with 40 ppm triazophos at 34°C approximately doubled compared with untreated insects. Furthermore, the triazophos-induced fecundity enhancement at 34°C was significantly greater than that at 26°C, and the number of eggs laid for mating pair of adult males at 34°C with adult females under 34°C (♂34 × ♀34) were significantly greater than that of adult males at 26°C (♂26 × ♀34), suggesting that this insecticide enhances the resistance of brown planthopper to high-temperature stress. Insecticide-induced enhancement of reproductive capacity in brown planthopper under high temperatures should be of great concern, and it has important implications for forecasting future brown planthopper outbreaks as well as the pesticide-selection process.