Effectiveness of clear-cuttings in non-fragmented pine forests in relation to EU regulations for the eradication of the pine wood nematode

Abstract

1. The invasive pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the most serious threats to pine forests across the world. Detected in Europe in 1999, it has largely spread despite containment measures. 2. Following the European Union regulations, the requested eradication measure is to fell, remove and dispose of all susceptible plants within a clear-cut zone (CCZ) of a radius of 500 m around any infected tree. This measure is controversial since its effectiveness is questioned. 3. An individual-based model, describing the dispersal of the nematode vector and the nematode transmission, was used to estimate the relationship between the radius and the effectiveness of the CCZ at eradicating the PWN. 4. Clear-cutting of a 500-m radius is poorly effective in non-fragmented pine forests since it reduces the number of PWN transmissions by only 0.6%–11.5%. To significantly reduce the number of transmissions, the radius should be between 14 and 38 km, which is not technically nor ethically feasible. 5. Policy implications. Our results, based on model simulations at a fine spatial scale, prove that clear-cutting susceptible trees 500 m around any infested tree—as requested by EU regulation to eradicate the PWN—is not effective in large and continuous pine forests. Instead, strengthened surveillance and sanitation felling could be explored.