Exploring Common Hyperspectral Features of Early-Stage Pine Wilt Disease at Different Scales, for Different Pine Species, and at Different Regions

Pine wilt disease (PWD) is a devastating forest disease and has been listed as a quarantine pest in 52 countries around the world. Early identification of the affected trees and timely removal of them from the forest is crucial to control the spread. This study aims to explore the potential of hyperspectral data on early identification of PWD and exhibit the common spectral features, from early-infected tree crowns and needles, and from different species located in different regions. Two types of hyperspectral data were used and compared. One was using drone-based hyperspectral images with a spectral range of 400 – 1 000 nm and a resolution of 0.11 m. The images were analyzed at the individual-tree level. The other was using hyperspectral reflectance from sampled needles with a spectral range of 350 – 2 500 nm. It was used for the analysis at the needle level. We used linear discriminant analysis (LDA) to quantify the separability of spectral reflectance and first-derivative reflectance from the healthy and early-infected samples. The results showed that the red-edge bands were more sensitive than the other bands at both individual-tree and needle levels, and the first-derivative of red-edge bands achieved the best early recognition of the disease with 0.78, 0.72, and 0.85 accuracy at the individual-tree level for Chinese red pine and at the needle level for Japanese pine and Korean pine. We concluded that red-edge bands were the most informative bands with stable sensitivity at different scales and for different species.