Discriminating wheat aphid damage level using spectral correlation simulating analysis

Wheat aphid, Sitobion avenae F. is main aphid species infesting winter wheat in the filling stage in Northwest China, and it has severe impact on both wheat yield and quality. The study acquired hyperspectral data by ASD FieldSpec Pro spectrometer at the canopy level and aphid damage levels of samples in the filling stage of winter wheat. The spectral characteristics of wheat uninfected by aphid and healthy wheat were analyzed, then the correlation simulating analysis model (CSAM) which was established by a 2-dimensional coordinate system with average spectral of healthy wheat samples called also base spectrum as abscissa axis and the spectral of other samples as vertical axis respectively is developed and tried to monitor the aphid damage levels. It is concluded that the fitting curves obtained by the reflectance of samples relative to healthy wheat samples are near to straight line in the range from 400nm to 1000nm (R²>0.99), and the slopes of fitting lines decrease as aphid damage levels become serious. Moreover, the most sensitive band regions were selected out. The result shows that the correlation between the slopes of fitting line and aphid damage levels is the highest in the range from 400 nm to 810 nm (R²=0.89). Therefore, the CSAM can be sued to discriminate the aphid damage levels in the filling stage of winter wheat.