Data from: Predicting the spread of an invasive tree pest: the pine wood nematode in Southern Europe

1. Invasive tree pests are increasingly threatening forest ecosystems.
Understanding and controlling their spread presents a major challenge for
managers, researchers, and policy makers. In 1999, the pine wood nematode
Bursaphelenchus xylophilus, causal agent of pine wilt disease and native
to North America, was first detected in Europe, more precisely in south
western Portugal. Since then, it has spread to more than 30% of the
country, producing large-scale damages in Portuguese forests. 2. We
applied a new spatio-temporal network-based model to predict, at yearly
intervals, the natural spread of the pine wood nematode on the Iberian
Peninsula, as dispersed by the longhorn beetle Monochamus
galloprovincialis, its only known vector in Europe. We compared the model
predictions with independent observations of the natural spread of pine
wilt disease in Portugal between 2005 and 2015. We simulated the effect of
potential containment measures on the disease spread. 3. The model
predicted the status (infected or non-infected) of forest areas with 93%
accuracy, had 93% sensitivity and specificity, and AUC=0.96 (averages for
8 years with validation data). 4. Simulated clear-cut belts stopped the
spread only if they were wider than 30 km, although thinner belts delayed
invasion. Furthermore, clear-cuts were much more effective in slowing down
the invasion when reinforced, in the adjacent areas, by the reduction of
the vector beetle population through mass trapping and by the early
detection and removal of infected trees. 5. Model projections identified
areas through which the nematode is most likely to invade, by natural
means, the phytosanitary buffer zone established along the Portuguese
border, and Spain. 6. Synthesis and applications. In the absence of
effective containment measures, the pine wood nematode may naturally
spread into Spain in about 5 years. In less than 10 years, it may reach
the major forest and climatic corridors that provide a gateway for
subsequent expansion towards the rest of the Iberian Peninsula and, in the
longer term, towards other European countries. Our model can considerably
support management efforts by forecasting when areas are at highest risk
of vector-mediated invasion as well as the effects of specific control
measures on the disease spread.