Spectral characteristics of rice canopy infested with rice leaf folder
Journal
Proceedings of the 6th International Conference on Precision Agriculture and Other Precision Resources Management
Pages
1631-1643
Date Issued
2002-07
Author(s)
Chwen-Ming Yang
Ching-Huan Cheng
Jih-Zu Yu
Abstract
Reflectance spectra (350-2500 nm) of rice (Oryza sativa cv. TNG 67) canopy infested with various levels of rice leaf folder (Cnaphalocrosis medinalis) during the early grain-filling stage of the second growing season in 2000 in Wufeng, Taiwan, were measured and analysed using a field portable spectroradiometer. Infestations by the leaf folder were classified into six levels, i.e., 0 (healthy check), 1, 3, 5, 7, and 9, based on the percentages of damaged leaves. From the results of correlation intensity analysis, wavelengths of 691 and 2327 nm were selected to correlate with pest infestations. The reflectance at these two wavelengths was positively correlated with levels of infestation, with the coefficients of determination (R2) of 0.906 (P<0.003) and 0.924 (P<0.03), respectively. The normalized difference vegetation index (NDVI), the RED/NIR ratio (reflectance at red light minimum to reflectance at near-infrared maximum), and the RED/GREEN ratio (RED to reflectance at green light peak) were curvilinearly correlated with infestation levels. The determining factors (R2) were 0.957 (P<0.009), 0.953 (P<0.02), and 0.882 (P<0.05), respectively. By the multiple linear regression (MLR) analysis with six selected narrow bands, levels of infestation (Y) may be expressed as a function of green and red light variables as Y=-8.749-2.336R550 nm+5.099R691 nm (R2=0.989, P<0.002), where R550 nm is the reflectance at 550 nm and R691nm is the reflectance at 691 nm. The best 2-variable MLR model including GREEN, RED, and NIR was Y=-3.742-3.742RED+8.616GREEN (R2=0.963, P<0.01).
Event(s)
Proceedings of the 6th International Conference on Precision Agriculture and Other Precision Resources Management
Publisher
University of Minnesota, Precision Agriculture Center
Description
Includes papers and proceedings from the conference held July 14-17, 2002 at the Radisson Hotel South and Plaza Tower, Minneapolis
Type
conference paper