Use of hyper-spectral data for detection of rice leaf folder infestation

Hyperspectral data were applied for discriminating normal and damaged rice leaves due to rice leaf folder (Cnaphalocrocis medinalis Guenee). The reflectance from rice canopy infested by rice leaf folder (RLF) was studied at the booting stage in order to establish a monitoring method for RLF based on hyperspectral data at different insect infestation levels (0 - 80 percent). The hyperspectral reflectance of rice leaves was measured through full wavelength range from 350 to 2500 nm. The hyperspectral response characteristic analysis indicated that the RLF infested leaves presented a higher reflectance in the visible (430∼470 nm, 490∼610 nm and 610∼680 nm) and short wave infrared (2080∼2350 nm) region. A lower reflectance in the near infrared (780∼890 nm) and short wave infrared (1580∼1750 nm) region was observed in the affected leaves as compared to the normal leaves. The indices in near infrared region (NIR) region were better correlated than the indices in visible region. Simple ratio and Red Edge in NIR region were most sensitive indices having best correlation with RLF infestation levels (F-values 33.10 and 19.9) as compared to the transformed chlorophyll absorption ratio index in visible region having least correlation with infestation levels (F-value 2.10). The higher differences in the NIR regions indicated that this region is more useful for detection of insect pest infestation than the visible region of the spectrum.