Sélection - European Institute of Planted Forest

Pine wood nematode

Bursaphelenchus xylophilus
Synonym: Bursaphelenchus lignicolus

Host tree

Pine species and other coniferous trees. Some pines are very susceptible (Pinus pinaster, P. nigra, P. thunbergii, P. densiflora, P. taeda), while others are resistant (P. banksiana, P. palustris, P. rigida, P. elliottii). Species of fir (Abies), cypress (Chamaecyparis), larch (Larix), spruce (Picea), Douglas fir (Pseudotsuga) and cedar (Cedrus) may also be attacked by the nematode, although they generally do not die.

Identification

General wilting and yellowing of the needles, which remain on the tree and turn brown.
Quick death of the affected trees (30-90 days after the first visible symptoms), usually in summer. Some trees die the following spring.
Timber without resin.
B. xylophilus is not visible to the naked eye and can only be distinguished from other Bursaphelenchus species in specialised laboratories.

Damage

Infected trees in susceptible species will die.

Biology

In Europe B. xylophilus occurs in Portugal only (restricted to the Setúbal peninsula). It has only been found in Pinus pinaster. The vector of B. xylophilus in Portugal is Monochamus galloprovincialis (Coleoptera: Cerambycidae).
Adult Monochamus beetles can transport juvenile nematodes. The vector beetles introduce primarily the nematodes into a healthy tree through wounds caused by adult feeding.
In a suitable tree species and under favourable climatic conditions, the nematodes quickly multiply and move from the cambium into the xylem, where they kill the tree by blocking the water channels.
In dead trees, the nematodes feed on fungi, particularly on blue stain fungi.
Wilted trees become suitable for egg laying by Monochamus females with probable occurrence of secondary nematode transmission. The beetle larvae develop initially in the cambium and spend the winter inside the wood. In spring, the nematodes congregate near the pupal chambers and attach themselves to the adult beetles before they emerge.

Risk factors

High temperatures and dry growing seasons favour the intensification and spread of the nematode.

Pest management

Monitoring

Careful monitoring of new spots of pine decline with verification of the presence of the nematode in the trees.
Monitoring Monochamusbeetles flight with ethanol and monoterpene hydrocarbons baited traps or traps made of pine branches and logs.

Preventive measurements

Removal and destruction of infected trees before the spring emergence of Monochamus.
In the long term, breeding and planting of resistant pines.

Bursaphelenchus xylophilus