Reassessing the threat posed by pine wood nematode to UK forestry

Project leads  Dr Sarah Facey | Forest Research; Talor Witham | PhD Student, Forest Research and University of Reading

Lead organisation  Forest Research
Project status  Active (Duration 3 years)
Project funding  £210,000
Research outcome  Response
Context

Pine wilt disease (PWD) is a lethal wilting disease recognised as one of the most serious threats to conifer forestry worldwide. The disease is caused by the pine wood nematode (PWN) (Bursaphelenchus xylophilus), which travels between trees on the bodies of Cerambycidae monochamus beetles. PWN enter trees through beetle feeding wounds and egg notches, grow inside the trees and gather on developing beetles inside the wood, before the beetle emerges and travels to feed and mate, spreading the nematode further.

PWN has been intercepted on infested packaging material coming through UK ports and processors and could arrive in the UK. The UK has no indigenous Monochamus species, however, PWN is known to have formed new associations with native Monochamus beetles in countries outside of its native North American range. Other beetles in the UK display similar life history behaviours to Monochamus beetles and there is concern that they could act as alternative vectors for PWN. This is a horizon scanning PhD project that seeks to inform future forestry about the risks posed if PWN arrives in the UK.

Research aims and objectives
Aim

The project examines the relationship between Monochamus and PWN and assess the risk of UK longhorn and bark beetles as potential vectors of PWN.

Objectives:
  • Survey UK pine wood samples and associated beetles to assess the native nematode species present in the environment currently.
  • Characterise and compare the volatile organic cuticular compounds (VOCCs) to those found in Monochamus.
  • Perform experiments exposing PWN to a range of UK beetle cuticular extractions, both with and without the co-presence of Monochamus extractions to assess nematode responses to chemical cues.
  • Draw up actionable recommendations for PWN.
Expected outcomes
  • Peer reviewed journal articles.
  • Recommendations for policies regarding PWN in the UK.
Microscope image of a nematode worm

Pine wood nematode (PWN) under a microscope.

Glossary & Key Terms
Cerambycidae Monochamus beetles

A genus of longhorn beetles within the family Cerambycidae, known for their role as vectors of the pinewood nematode (Bursaphelenchus xylophilus), the causal agent of Pine Wilt Disease (PWD).

Cuticular extractions
The process of removing the cuticle, or outer layer, of a plant or insect, or the extraction of cuticular waxes from these cuticles.
Pine wilt disease (PWD)
A lethal wilting disease affecting conifer trees, caused by the pinewood nematode (PWN), (Bursaphelenchus xylophilus). It is considered one of the most serious global threats to conifer forestry. The nematode spreads between trees via Monochamus beetles (family Cerambycidae), which carry the nematode on their bodies. The PWN enters trees through beetle feeding wounds and egg notches, proliferates inside the tree, and then transfers to developing beetles within the wood. When these beetles emerge and move to new trees to feed and mate, they further spread the nematode, perpetuating the disease cycle. For more information, see Pine wood nematode (Bursaphelenchus xylophilus) – Forest Research.
Pine wood nematode (Bursaphelenchus xylophilus)

A microscopic roundworm, scientifically named Bursaphelenchus xylophilus, that causes Pine Wilt Disease (PWD). It is a pathogenic organism that infects conifer trees, particularly pines, by entering through wounds created by Monochamus beetles during feeding or egg-laying. Once inside the tree, the nematode multiplies rapidly, disrupting water transport and leading to tree wilting and death. PWN also uses beetles as vectors, hitching rides on their bodies to spread from one tree to another, continuing the disease cycle. For more information, see Pine wood nematode (Bursaphelenchus xylophilus) – Forest Research.

Vector
An organism that transmits a pathogen, disease, or parasite from one animal or plant to another.
Volatile Organic Cuticular Compounds (VOCCs)
Chemical cues given off by the UK beetle species (potential carriers/vectors).

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