Abstract: To investigate the current status of the resistance to insecticides of rice planthoppers in Zhejiang province, rice stemdipping method was used for detecting the susceptibilities to insecticides of brown planthopper, Nilaparvata lugens(St-l), collected from Jiaxing city, and whitebacked planthopper, Sogatella furcifera(Horv-th), collected from Hangzhou city, and small brown planthopper, Laodelphax striatellus(Fallén), collected from Jiaxing city and Changxing city. The results showed that the Jiaxing population of N. lugens had developed a high level of resistance to imidacloprid with 615.9-814.2 fold, and to thiamethoxam with 66.2 fold, and to buprofezin with 13.0 fold, and still susceptible to nitenpyram. The susceptibility of the Hangzhou population of S. furcifera to chlorpyrifos was dropped 9.5 times from 2008 to 2010, which suggested a rapid evolution of resistance of S. furcifera to chlorpyrifos. The susceptibilities of the Changxing population of L. striatellus to thiamethoxam, chlorpyrifos and imidacloprid were reduced 1.6, 2.5 and 2.3 fold, respectively, from 2007 to 2010 or 2011, and toxicities of thiamethoxam and chlorpyrifos against the Changxing population of L. striatellus were slightly higher than those against the Jiaxing population. Based on the bioassay data, strategies of the application of insecticide in field and insecticide resistance management for the control of rice planthoppers were also proposed.

Key words: brown planthopper, whitebacked planthopper, small brown planthopper, susceptibility, resistance