Changes of Insecticide Susceptibility of the White Backed Planthopper Sogatella furcifera HORVATH (Homoptera:Delphacidae) and the Brown Planthopper Nilaparvata lugens STAL (Homoptera:Delphacidae)

Insecticide susceptibility of the white backed planthopper, Sogatella furcifera HORVATH, (WBPH), and brown planthopper, Nilaparvata lugens STAL, (BPH), was surveyrd by the topical application method in 1980 and 1987. Comparing the data obtained in these experiments with previous data, the susceptibility of the WBPH to organophosphate and carbamate insecticides was found to have decreased with years. Susceptibility of the BPH to organophosphates in 1987 was greater than that in 1980. The susceptibility of both insects to p, p'-DDT decreased with years, but that to lindane was almost the same as in 1967. In 1987 LD50 values of the WBPH and BPH to synthetic pyrethroids were also evaluated.