Study on the number of Bursaphelenchus xylophilus carried by Monochamus saltuarius adult

  Objective  The amount of Bursaphelenchus xylophilus carried by vector insects has an important impact on the transmission and damage of pine wilt disease, so it is necessary to clarify the carrying amount of Monochamus saltuarius vectoring B. xylophilus in China.

  Method  The number of B. xylophilus carried by M. saltuarius was investigated in Dahuofang Experimental Forest Farm in Fushun City, Liaoning Province of northeastern China in 2018 to 2020. Pinus koraiensis trees infected by M. saltuarius were sawn into one meter long logs, sealed with wax at both ends to retain moisture, and placed in cages. The newly emerged M. saltuarius was collected every day. Meanwhile, the M. saltuarius was collected from infected P. koraiensis by hanging sentinel traps and shock-dropping methods, and brought to the laboratory. All the collected live M. saltuarius trees were dissected into three parts: head, thorax and abdomen to separate nematodes by the Bayman funnel method, then the number of B. xylophilus was counted.

  Result  58 vectors were tested carrying B. xylophilus among 160 newly emerged adults of M. saltuarius, accounting for 36.25% of the total. The average number of B. xylophilus carried by each M. saltuarius was 336.74, and the maximum number was 5 560. The average number of B. xylophilus carried by each female adult and male adult was 458.52 and 191.54, respectively, with no significant difference between male and female. 38 vectors were tested carrying B. xylophilus among 274 M. saltuarius adults collected in forest, accounting for 13.87% of the total. The average number of B. xylophilus carried by each M. saltuarius was 214.92, and the maximum number was 2 486. The average number of B. xylophilus carried by each female adult and male adult was 161.81 and 280.53, respectively, with no significant difference between male and female. The average number of B. xylophilus in thorax, head, and abdomen of M. saltuarius was 35.88, 0.88, and 0.34, respectively. The number of B. xylophilus in vector’s thorax was much higher than that in the other two parts.

  Conclusion  It is found that the number of B. xylophilus carried by M. saltuarius in China was much lower than M. saltuarius in Japan and M. alternatus in this study. There was no significant difference in the carrying amount between male and female adults of M. saltuariu, and B. xylophilus was mainly distributed in the thorax of the vector.