Pinus pinea: a natural barrier for the insect vector of the pine wood nematode?

Abstract

Key message: In mixed stands of Pinus pinaster and Pinus pinea, fewer insect vectors of the pinewood nematode (PWN) were captured than in pure P. pinaster stands. This finding has practical implications for PWN disease management, including the recommendation to improve the diversity of maritime pine plantations and to conserve stone pines in infected areas.

Context: The PWN is an invasive species in European pine forests, being vectored by the longhorn beetle Monochamus galloprovincialis. The presence of less preferred host trees may disrupt the insect vector dispersal and slow the spread of the disease.

Aims: The aim of the study was to compare the abundance of M. galloprovincialis in pure stands of Pinus pinaster, a preferred host tree, pure P. pinea stands, a less preferred host, and mixtures of these two species.

Methods: We selected 20 mature pine stands varying in % P. pinaster and % P. pinea in Spain. In each stand, we installed 3 pheromone traps to catch M. galloprovincialis. We related trap catches to stand and landscape composition.

Results: The level of capture of M. galloprovincialis was highest in pure P. pinaster stands and decreased with increasing proportion of P. pinea.

Conclusions: The presence of stone pine mixed with maritime pine significantly reduces the local abundance of the PWN insect vector. The most plausible mechanism is that P. pinea emits odors that have a repulsive effect on dispersing beetles.