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Pine wood nematode
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Subclass: Tylenchia
Order: Aphelenchida
Superfamily: Aphelenchoidoidea
Family: Parasitaphelenchidae
Subfamily: Bursaphelenchinae
Genus: Bursaphelenchus
Species: B. xylophilus
Binomial name
Bursaphelenchus xylophilus

Bursaphelenchus xylophilus (pine wood nematode or pine wilt nematode)(PWN) is a nematode (worm) that infects pine trees and causes pine wilt.[1][2] [3] It originates from North America, but has now spread to Europe and East Asia and has become a worldwide quarantine pest.

It is particularly damaging to matsutake mushroom cultivation.



Thought to be native to North America, the PWN has spread over seas to countries such as Japan, China, Vietnam, Australia, and Portugal, where it has caused severe damage in certain species of pine. Perhaps the most notable PWN epidemic has occurred in Japan, where pine wilt is credited with the destruction of some 26 million cubic meters of timber since WWII [4][5][6][7].


Distinguishing PWN from other non-pathogenic species within the same genus (Bursaphelenchus) is challenging due to highly similar morphological features, but a positive ID can be achieved using molecular analyses such as RFLP [4][8].

Life Cycle/ reproduction

The basic propagative lifecycle of the PWN is typical of most nematode species, having four vermiform juvenile stages (J1-J4), followed by an amphimictic (male and female) adult stage.This basic life cycle takes place in dead or dying wood when the nematodes are said to be in there “mycophagous” phase, feeding on fungus within the wood and NOT on the wood itself. The PWN is unable to travel outside of the wood by itself, and in order to reach another host tree (living or dead) it must be carried by an insect vector [4][8].


Though the PWN is known to be vectored by a number of bark beetles and wood borers, it seems to be most often associated with species in the genus Monochamus, widely referred to as “pine sawyers”. Pine sawyers lay their eggs in the bark of dead timber. The growing larva feeds on the wood, and within the resulting cavity develops into an adult pupa. The J3 stage of the PWN congregate in the cavity around the pine sawyer pupa, molt into J4 (dauer stage) juveniles, and then migrate into the trachea of the adult beetle through its spiracles. During this “dispersive stage” the beetle may transport the PWN in one of two ways. In “secondary transmission” during vector oviposition, the nematode is transported to another dead tree and continues in the mycophagous phase [4][8].

Host parasite relationship

In “primary transmission” when the beetle feeds on susceptible host pines, the PWN will enter the tree and feed on the epithelial cells which line the resin ducts. This is referred to as the “phytophagous” phase of the PWN, and will result in pine wilt. Under peak conditions pine wilt can become apparent within a few weeks after infection, with browning of the needles and eventual death of the tree. Though the susceptibility of many species of pine is still a matter of contention, susceptibility has been proven (using Koch’s postulates) in a few species, which includes Scotch, Slash, Japanese red, and Japanese black pines. The Slash pine is the only susceptible species native to North America, and its susceptibility has been shown to be relatively week compared to foreign pines. Because of this the direct economic impact due to pine wilt, in this part of the world, is limited to predominantly landscaping settings [4][8].


Protective embargoes placed by the EU on untreated lumber transported from the U.S. and Canada have resulted in more indirect economic losses (2,3). Because there is no cure for pine wilt, management practices have concentrated on preventing the spread of the PWN. Infected trees are cut and either burned or chipped, soft wood timber is stripped of its bark to prevent oviposition by vectors, and all lumber shipped overseas is either fumigated or kiln dried. Despite these preventative measures the PWN has recently made in appearance in Portugal, and threatens to spread to other countries in Europe [4][5][6][7][8].


  1. ^
  2. ^ UC Davis
  3. ^ Online Gardener
  4. ^ a b c d e f Dwinell L.D., Nickle W.R. 2004. An Overview of the Pine Wood Nematode Ban in North America. USDA
  5. ^ a b Mota M.M., Vieira P.C. 2008. Pine Wilt Disease in Portugal. NemaLab-ICAM, Department of Biology, University of Evora. Evora, Portugal
  6. ^ a b Mota M.M., et al. 2008. Pine Wilt Disease: A Worldwide Threat to Forest Ecosystems. Springer ISBN 9781402084546
  7. ^ a b Suzuki K. 2002. Pine Wilt Disease: a threat to pine forest in Europe. Dendrobiology, Vol. 48. 71-74
  8. ^ a b c d e Cram M., Hanson J. How to Identify and Manage Pine Wilt Disease and Treat Wood Products Infested by the Pinewood Nematodes. USDA


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