Identification of damage by diseases and insect pests in winter wheat.

Crop diseases and insect pests were an important factors in crop growth,yield and quality.Non-destructive monitoring of crop diseases and insect pests was a basis of dynamic management by remote sensing technology.The canopy reflectance of wheat powdery mildew,wheat stripe rust and aphid were measured by using ASD hand-held spectroradiometers.The reflectance data was transformed by the method of the first differential coefficient,logarithm and normalization,then stepwise discriminate analysis and hierarchical clustering were used to identify the difference in plant diseases and insect pests.The results suggested that bands selected from stepwise discrimination analysis mainly lied along the blue,green,red and near-infrared bands.In addition to the blue,green,red and near-infrared bands,the spectral bands along the blue-green edge,green-red edge and red curves were selected by the hierarchical clustering.Plant diseases and insect pests could be identified more accurately by using selected bands than the original data,with maximum identification accurate up to 90.6%,and the bands lying along the edges had important information for discrimination of plant diseases and pests.The spectral data,dealt with the transformation of logarithm and differential coefficient,could achieve better accuracy than others.