Phenomics-based Evaluation of the Effect of Emamectin Benzoate Injections on the Health Status of Pinus massoniana Forests

This study was conducted in 2022 at the Guanzhuang State-owned Forest Farm in Shaxian County, Sanming City, Fujian Province, focusing on a 14-year-old pure plantation of second-generation Masson pine（Pinus massoniana） seed orchard.The experiment involved trunk high-pressure injection of 2% EB emulsion, with a non-injection group serving as the control.A DJI Phantom 4 RTK was used as the flight platform.Spectral features related to the health status of different Masson pine trees were extracted prior to injection, and an artificial intelligence model was employed to classify all individual trees in the sample area into three categories: healthy, lightly infected（by nematodes）,and severely infected（by nematodes）.The study focused on the normalized difference vegetation index（NDVI）,which was highly positively correlated with health status, and the near-infrared（NIR） and Red Edge（Red Edge） spectral features, which were negatively correlated with the severity of pine disease.Changes in health status and disease severity were analyzed at 90,120,and 180 days after injection of 2% EB emulsion.The results showed:（1）The mortality rate of the Masson pine stand decreased by 80% after injection of 2% EB emulsion comPAred to the control group.（2）ComPAred to the control group, the overall health status of Masson pine trees significantly improved 180 days after injection of 2% EB emulsion, as evidenced by a highly significant increase in NDVI and the modified simple ratio（MSR） values（P＜ 0.01）.ComPAred to pre-injection levels, the NIR,Red Edge and NDVI values of severely infected trees increased by 1.18 times, 1.36 times and 1.55 times, respectively（P＜ 0.05）.The corresponding values for healthy and lightly infected trees also increased by 1.42 times, 1.20 times and 1.24 times（P＜ 0.05） and 1.08 times, 1.09 times and 1.22 times（P＜ 0.05）,respectively.ComPAred to the control group, the values for healthy, lightly infected, and severely infected trees increased significantly by 1.17 times, 1.34 times and 1.39 times, respectively（P＜ 0.05）.（3）Over time, the NIR,Red Edge,and NDVI values in the control group showed no significant changes or slight declines.The results demonstrate that trunk high-pressure injection of 2% EB emulsion can effectively improve the health status of Masson pine stands and significantly control the damage caused by pine wilt disease, which is consistent with field observations of tree mortality.