Effect of nitrogen application combined with silicon on density of Sitobion avenae and contents of biochemical materials of winter wheat at the late growth stage

To determine the effects of nitrogen (N) application combined with silicon (Si) on population density of S. avenae and contents of biochemical materials of winter wheat at the late growth stage, two nitrogen levels (180 kg/ha and 270 kg/ha) combined with three silica levels (0 kg/ha, 75 kg/ha and 150 kg/ha) were randomly designed in fullybalanced blocks. The result shows that the density of wheat aphids is increased under the nitrogen application, which closely relates to the decreases of the average contents of soluble sugar and total phenolic of wheat leaves and ears and tannin contents of wheat leaves, and the increases of soluble protein contents of wheat leaves and ears. The effects of the silicon application on reducing the population density of aphids would be contributed to the increases of the average contents of soluble sugar, total phenolic and tannin of wheat leaves and ears. The effects of the high silicon application on reducing the high aphids population density induced by the high nitrogen level could be contributed to the high silicon application which reduces the effects of nitrogen on the contents of soluble sugar of wheat leaves and ears and tannin content of wheat leaves. Under the low N level, the population density of S. avenae is significantly reduced by the combined application with the low level of silicon, and this effect could be contributed to the high soluble sugar content in wheat ears. However, under the high N level, it should be combined with the high level of silicon to reduce the population density of S. avenae effectively, and the application contributes to high soluble sugar contents in wheat leaves and eras and tannin content in leaves.