Reduction of the natural enemy population by deltamethrin and imidacloprid leads to the resurgence of brown planthopper (Nilaparvata lugens, Hemiptera: Delphacidae (Stal)) in rice

Brown planthopper (BPH), Nilaparvata lugens (Stal) is a monophagous and one of most devastating pest of rice. Application of insecticides is inevitable to control the infestation of BPH on rice crops. However, the indiscriminate use of various insecticides in rice is leading to pest resurgence. Several factors have been connected to the resurgence of brown planthoppers, especially the reduction in natural enemies and changes in plant nutrition after insecticide application. Hence, in the present study, we studied the resurgence of BPH post application of different insecticides in rice and assessed the impact of insecticides on natural enemy population during Rabi 2022-23. Among nine insecticides tested, two insecticides viz., deltamethrin 11 EC @ 15 g a.i/ha (44.70%) and imidacloprid 17.8 SL @ 25 g a.i/ha (23.01%) significantly increased the population of N. lugens over untreated check and consequently resulted in higher BPH resurgence. A greater reduction in predatory mirid bugs and spiders was observed in the deltamethrin and imidacloprid treated groups compared to the untreated check. In conclusion, we found that deltamethrin and imidacloprid induce the BPH resurgence in rice compared to other tested insecticides and the observed resurgence was partly due to the reduction of natural enemies.