Assessment of dwarf mistletoe (Arceuthobium sichuanense) infection in spruce trees by using hyperspectral data

Summary Dwarf mistletoe (Arceuthobium spp.,Viscaceae) (DM), a hemiparasitic plant, is nutritionally dependent upon its host tree and causes tree mortality in forests worldwide. Dwarf mistletoe infection results in physiological changes in the host, eventually causing the death of the host tree. In this study, we evaluated the changes in leaf reflectance of spruce trees, Picea crassifolia, infected by DM (Arceuthobium sichuanense) with ground‐based hyperspectral technology. A total of 112 sample sites were selected for analysis in the eastern part of Qinghai Province, China, including healthy spruce tree, light DM‐infected spruce tree, moderate DM‐infected spruce tree and high DM‐infected spruce tree in each site. The results showed that leaf reflectance was significantly different among healthy spruce, DM‐infected spruce, DM and dead spruce in the near‐infrared regions ranging from ~750 to 900 nm. Dwarf mistletoe infection resulted in the increase of leaf reflectance of host tree, and the intensity of DM infection was positively related to reflectance. However, five selected hyperspectral indices that commonly used to estimate the physiological status of plants (carotenoid reflectance index, photochemical reflectance index, normalized difference vegetation index, structure‐insensitive pigment index and water index) were not linearly correlated with the intensity of DM infection. Collectively, the hyperspectral characteristics of spruce infected by DM can be potentially used to detect DM‐induced changes on a landscape scale with satellite remote sensing, which can be used as an efficient advanced tool for DM disease monitoring.