Disentangling the drivers of invasion spread in a vector-borne tree disease

Yutaka Osada, Takehisa Yamakita, Etsuko Shoda-Kagaya, Andrew M. Liebhold, Takehiko Yamanaka

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Pine wilt disease (PWD) invaded southern Japan in the early 1900s and has gradually expanded its range to northern Honshu (Japanese mainland). The disease is caused by a pathogenic North American nematode, which is transmitted by native pine sawyer beetles. Recently, the disease has invaded other portions of East Asia and Europe where extensive mortality of host pines is anticipated to resemble historical patterns seen in Japan. There is a critical need to identify the main drivers of PWD invasion spread so as to predict the future spread and evaluate containment strategies in newly invaded world regions. But the coupling of pathogen and vector population dynamics introduces considerable complexity that is important for understanding this and other plant disease invasions. In this study, we analysed historical (1980–2011) records of PWD infection and vector abundance, which were spatially extensive but recorded at coarse categorical levels (none, low and high) across 403 municipalities in northern Honshu. We employed a multistate occupancy model that accounted both for demographic stochasticity and observation errors in categorical data. Analysis revealed that sparse sawyer populations had lower probabilities of transition to high abundance than did more abundant populations even when regional abundance stayed the same, suggesting the existence of positive density dependence, that is an Allee effect, in sawyer dynamics. Climatic conditions (average accumulated degree days) substantially limited invasion spread in northern regions, but this climatic influence on sawyer dynamics was generally weaker than the Allee effect. Our results suggest that tactics (eg sanitation logging of infected pines) which strengthen Allee effects in sawyer dynamics may be effective strategies for slowing the spread of PWD.

Original languageEnglish
Pages (from-to)1512-1524
Number of pages13
JournalJournal of Animal Ecology
Issue number6
Publication statusPublished - 2018 Nov


  • Allee effect
  • Bayesian MCMC
  • multistate occupancy model
  • pine sawyer Monochamus alternatus
  • pine wilt disease (PWD)
  • pine wood nematode Bursaphelenchus xylophilus
  • state-space modelling

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


Dive into the research topics of 'Disentangling the drivers of invasion spread in a vector-borne tree disease'. Together they form a unique fingerprint.

Cite this