Abstract:Using ASD hand-held spectroradiometers and low altitude remote sensing system measured the canopy reflectance of wheat damaged by Blumeria graminis f.sp. tritici and, at the same time, scored the disease index (DI). The correlation between reflectance and DI and normalized difference vegetable index (NDVI) and DI was calculated. The results show that the correlation between reflectance and DI is significant at the stage of grouting. The result of in-field measurement shows that the correlation between near infrared reflectance and DI is higher than that of green band with the correlation coefficients of 0.79 and 0.54, respectively. The reflectance correlation between red, green and blue bands decreased in the order with the correlation coefficients of 0.79, 0.75 and 0.62, respectively. The reflectance of low altitude remote sensing was well correlated with NDVI moreover. The correlation coefficients are 0.70, 0.68 and 0.54 for blue, red and green band, respectively. This indicates that it is prospective in using remote sensing to monitor the development of wheat powdery mildew in the fields non-destructively and helpful in the investigation of occurrence area of the disease.