Transmission of pine wilt disease from dead pine trees in the forest areas of Kangxian county, Gansu province

In 2021, Gansu province confirmed its first case of pine wilt disease in Kangxian county, Longnan city, making it a new epidemic zone in the westward expansion of the disease within China. To further clarify the transmission patterns and characteristics of pine wilt disease in Kangxian county, the number of dead pine trees, the time of death, the number of the emergence hole of Monochamus alternatus were investigated, and the number annual changes of M. alternatus populations were monitored in the disease‑affected areas of Kangxian county from 2021 to 2023. The results indicated that the number of dead pine trees and M. alternatus populations decreased annually after three consecutive years of cleaning up infected pine trees, among which the number of dead pine trees with emergence holes decreased more significantly. There was significant correlation between the spread of pine wilt disease and the time of death. Dead pine trees were the common host and medium for both the pathogenic nematode and its M. alternatus, playing a closed‑loop chain bearing and carrying function in the disease infection cycle, and having strong epidemic transmission. Emergence hole of M. alternatus were not detected on healthy pine trees or newly dead pine trees in current year.Consequently, newly dead pine trees do not transmit the epidemic in current year in Kangxian county, Gansu province. These results provided support for formulating local epidemic prevention and control strategies and technical measures for the removal of infected trees.