Modeling Water Stress As An Indicator Of Red Palm Weevil Infestation Using Field Sampling, Worldview-3 Reflectance, And Laboratory Analysis

This study focuses for the first time on the water content modeling as an indicator for red palm weevil (RPW) stress-attacks using field sampling, Worldview-3 (WV-3) reflectance measurements, water content estimation at the laboratory (WC-(Lab)), several water stress indices (WSI) and statistical analysis. Based on field identification and sampling, 100 date palm trees were considered and divided into four classes of RPW stress-attacks: dead, severely attacked, moderately attacked, and healthy trees (young and mature trees). Spectral measurements were acquired over each sample using Analytical Spectral Devices (ASD). Then, they were resampled and convolved using WV-3 spectral response profiles and the Canadian radiative transfer code (CAM5S). For model calibration, only 80 samples were considered, while 20 samples were used for validation purposes. Obtained results indicate that the proposed models based on PTWSI-4 and SRWI offer an important alternative to discriminate among different levels of RPW stress-attack. They discriminate significantly among the considered stress classes (R-2 >= 0.85) using second order regression (p < 0.05). The validation of PTWSI-4 model revealed a significant correlation with the WC-(Lab) values (R-2 of 0.95), and an acceptable RSME of 8.5 %.