Changes in the uptake function of the rice root to nitrogen, phosphorus and potassium under brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae) and pesticide stresses, and effect of pesticides on rice-grain filling in field

Abstract

Effects of different BPH densities and pesticide applications on the uptake of nitrogen (N), phosphorus (P) and potassium (K), by the root system were investigated using a hydroponics culture. Infestations of 30 BPH had a significant effect on the uptake function of the rice root. A high dose (225 g.a.i. ha −1) of jingganmycin reduced the uptake of P and K significantly, but there was little effect on the uptake of N. At a low dose (15 g.a.i. ha −1) of imidacloprid the uptake of P and K was promoted significantly. There was also a significant interaction effect between BPH density and pesticide treatments. Field experiment during rice-grain filling showed that both low and high doses of imidacloprid reduced active growth stage (Δ t) and maximum (K) of grain growth of superior grains significantly and a high dose reduced K and growth rate of inferior grains significantly. All doses of imidacloprid and jingganmycin significantly reduced accumulative grain weight during Δ t. A high dose of imidacloprid reduced the growth rate of inferior grains significantly.