Sublethal effects of four insecticides on the reproduction and wing formation of brown planthopper, Nilaparvata lugens.

BACKGROUND The brown planthopper (BPH), Nilaparvata lugens Stål, is a major rice pest in many parts of Asia. Neonicotinoids such as imidacloprid and dinotefuran are widely used for control of this pest, and resistance to these insecticides has developed in recent years. This pest has also been widely exposed to triazophos and fenvalerate, although these insecticides are not used for the control of the pest directly. Here, the effects of sublethal doses of these four insecticides on the reproduction and wing formation in BPH were examined. RESULTS Imidacloprid and dinotefuran reduced the fecundity of BPH to 68.8% and 52.4% in macropterous families, and to 57.9% and 43.1% in brachypterous families, when compared with the untreated controls. By contrast, triazophos and fenvalerate increased fecundity. In both macropterous and brachypterous families, sublethal doses of imidacloprid and dinotefuran showed significant induction of macropterous adults. CONCLUSION Imidacloprid and dinotefuran could reduce the fecundity of BPH to a significant extent, demonstrating further activity against this pest in addition to their direct toxicity. The significant induction of macropterous adults by sublethal doses of imidacloprid and dinotefuran is of importance in the management of this pest, particularly in the areas of predicting the size of emigrating populations and the numbers of insects likely to occur in newly colonized areas.