Insecticide application and its effect on the density of rice planthoppers, Nilaparvata lugens and Sogatella furcifera, in paddy fields in the Red River Delta, Vietnam

Abstract

The brown planthopper, Nilaparvata lugens, and the white-backed planthopper, Sogatella furcifera, are significant pest insects for rice. Both species are able to survive year-round in northern Vietnam's Red River Delta, which includes a large rice-producing region. This study aimed to evaluate insecticide use by farmers and its effect on the density of planthoppers in the region. Through interviews conducted with farmers in study sites in Nam Dinh (ND) and Vinh Phuc (VP) Provinces, we learned that farmers frequently used imidacloprid, fipronil, and emamectin-benzoate in ND and pymetrozine and thiamethoxam in VP. Farmers applied insecticides when the local government announcements regarding plant protection were broadcast. Generalized linear model analysis indicated that the selective insecticides applied did not contribute to reducing the densities of planthoppers in the farmers' fields. Our results indicate the possible development of insecticide resistance by planthoppers or improper insecticide application by farmers.