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Pine wilt disease (PWD) is greatly serious to Pinus, and there are still no effective therapeutic measures at present. It is necessary to explore a method of early diagnosis of PWD and to study rehabilitation treatment technology for diseased plants diagnosed early. This paper searched for infected pine trees in natural pine forests according to various subtle symptoms and divided the disease development stages. Different doses of 20% emamectin benzoate were injected at different stages, and the symptom development of pine trees was observed after injection. According to different external symptoms, the stage after being infected by PWD was divided into early stage I and II, middle stage I and II, late stage. It was shown by the results that the diagnostic rate of initial diagnosis based on the symptoms of early stage II was as high as 80%. Additionally, for early stage infected pine trees, an injection of 5–10 mL of 20% emamectin benzoate can inhibit the expansion of symptoms of PWD. One year after injection of 20 mL and 10 mL of 20% emamectin benzoate, the residues measured in the lateral branches 4 m above the injection point were 0.18 mg kg−1 and 0.06 mg kg−1, respectively. In summary, the characteristics of early stage II are ideal for identifying early infection, it has a certain therapeutic effect on early infected pine trees by injection of emamectin benzoate.
