Dynamic Changes of Resistance to Fipronil and Neonicotinoid Insecticides in Brown Planthopper,Nilaparvata lugens(Homoptera:Delphacidae)

The resistances to the phenyl pyrazole (such as fipronil),neonicotinoid and insect growth regulator insecticides (buprofezin) in brown planthopper,Nilaparvata lugens (Stl) were monitored by rice-stem dipping method during 2006 to 2008. Results showed that N. lugens sharply developed resistance to fipronil following its immigration route in 2008. The levels of resistance to Fipronil in 10 immigration populations from 6 provinces in the Yangtze River Delta areas and the back-migration populations in Shaoguan and Shenzhen of Guangdong were moderate (resistance ratio 15.0-fold to 32.5-fold) and high (66.9-fold to 73.7-fold),respectively,higher than those of all 6 field populations from 5 provinces in 2006(2.6-fold to 5.8-fold) and 11 populations from 9 provinces in 2007 (3.2-fold to 8.4-fold). The above results suggest that N. lugens would develop a higher level of resistance to fipronil in most rice-growing areas in China during 2009 to 2010. All populations collected in 2006-2008 showed high or extremely high level of resistance to imidacloprid,of which the resistance levels of 13 populations from 8 provinces in 2008 were 210.1-fold to 381.7-fold,though the resistance level dropped slightly in the following 3 years comparing with the extremely high level in 2005 (277-fold to 811-fold). For other neonicotinoid insecticides such as hiamethoxam,nitenpyram and dinotefuran,the resistance ratios were in the range of 2.0-fold to 15.8-fold,0.7-fold to 4.8-fold,and 0.6-fold to 2.8-fold,respectively. All the populations were susceptible or low-level resistant to buprofezin (3.0-fold to 11.9-fold). In recent years,widespread and intensive use of fipronil for controlling two classes of migratory rice pest insects (brown planthopper/white-backed planthopper and rice leaf roller) might be a major reason for fipronil resistance out-breaking in N. lugens. Therefore,to prevent insecticide resistance in N. lugens from out-breaking again,insecticide resistance management strategy including alternating and rotating insecticides without cross-resistance need to be established.