Comparison of transmission of the pine wood nematode, Bursaphelenchus xylophilus, via two different pathways from Monochamus alternatus to host trees

What is it about?

The pine wood nematode (Bursaphelenchus xylophilus) is a tiny animal and causes pine wilt disease, which kill a huge amount of trees of susceptible pine species in East Asia and Western Europe. It is transmitted to host trees by longhorned beetle adults of the genus Monochamus. There are two primary transmission pathways; one is to healthy trees via feeding wounds by vectors and the other is to dying or recently dead trees via the oviposition wounds. To determine the ratio of nematodes transmitted via the different pathways, M. alternatus female adults were reared on fresh pine twig sections and wood pieces with the bark made favourable to oviposition (Pinus densiflora). Of B. xylophilus transmitted to twig sections and wood pieces after beetles begin the reproductive activity, 38.7 % was transmitted to twig sections and 61.3 % to wood pieces. Comparing the pathogenic nematode and a non-pathogenic, relative nematode (B. mucronatus) indicated that the pathogenic species had 9.7 times higher likelihood of feeding-related transmission to oviposition-related transmission than the non-pathogenic species. Since the nematode transmission to healthy trees via feeding wound results in tree death, mature beetles are considered to be related to the incidence of pine wilt disease and the dispersal studies on mature beetles would help to predict the expansion rate of areas affected by the disease in the current year.

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