Differential Resistance and Cross-Resistance to Three Phenylpyrazole Insecticides in the Planthopper Nilaparvata lugens (Hemiptera: Delphacidae)

ABSTRACT Cross-resistance to two fipronil analogs, butene-fipronil and ethiprole, was detected in fipronil-resistant field populations and a resistant laboratory strain of the planthopper Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), although the two analogs have not been used widely in rice-growing areas in China. The results showed that six field populations with 23.8–43.3-fold resistance to fipronil had reached a higher level of cross-resistance to ethiprole (resistance ratio [RR] = 47.1–100.9-fold) and had a minor level of cross-resistance (RR = 3.4–8.1-fold) to butene-fipronil. After 10 generations of selection, the RR to fipronil increased from 7.3-fold to 41.3-fold. At the same time, the insect increased cross-RR to ethiprole from 16.3-fold to 65.6-fold, whereas it had only minor increase in cross-resistance to butene-fipronil from 2.8-fold to 4.0-fold. These results confirmed that fipronil-resistant N. lugens could develop a higher level of cross-resistance to ethiprole, although it still ma...