Bursaphelenchus xylophilus

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Bursaphelenchus xylophilus
Bursaphelenchus xylophilus spicule.jpg
male with spicule visible
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Aphelenchida
Family: Parasitaphelenchidae
Genus: Bursaphelenchus
Species:
B. xylophilus
Binomial name
Bursaphelenchus xylophilus
(Steiner & Buhrer 1934) Nickle 1981

Bursaphelenchus xylophilus, commonly known as pine wood nematode or pine wilt nematode (PWN), is a species of nematode that infects trees in the Pinus genus of coniferous trees and causes the disease pine wilt. [1] [2] While native to North America, it spread in the early 20th century to Japan and in the latter half of the century to other areas of Asia, including China, Taiwan, and Korea, as well as to Europe, including Portugal and Spain. [2] [3]

Contents

History

Pine mortality in Japan was first reported by Munemoto Yano (矢野宗幹) in Nagasaki prefecture in 1905. [4]

The nematode was first discovered in the timber of longleaf pine (Pinus palustris) in Louisiana, United States. Steiner and Burhrer reported that the nematode was a new species, and they named it Aphelenchoides xylophilus in 1934. [5] In 1969, Japanese plant pathologists Tomoya Kiyohara (清原友也) and Yozan Tokushige (徳重陽山) discovered many unfamiliar nematodes on dead pine trees around the Kyushu islands in Japan. [6] Then, they experimentally inoculated the nematode to healthy pine and other conifer trees and observed them. The healthy pine trees were killed—especially Japanese red pine ( Pinus densiflora ) and Japanese Black pine (P. thunbergii). However, Jack pine (P. banksiana), Loblolly pine (P. taeda), Sugi redwood (Cryptomeria japonica), and Hinoki cypress (Chamaecyparis obtusa) trees were able to survive. [7] In 1971, the researchers concluded that the nematode was the pathogen was the primary contributor to the high mortality of Japanese pine trees.

In 1972, Yasuharu Mamiya (真宮靖治) and Kiyohara incorrectly claimed that the nematode was a new species, which they named Bursaphelenchus lignicolous. [8] A 1981 reclassification united the American and Japanese forms as B. xylophilus. [9]

Pine wilt nematode epidemics have occurred in Japan, particularly during warm, dry summers. [10] [11] [12] [13]

In the late 1970s and 1980s, the nematode was observed to have spread to other countries of Asia outside of Japan, including China, Taiwan, and Korea, and later observed in Europe, including Portugal and Spain. The forests of Portugal have been particularly impacted, as the most abundant species, the maritime pine, comprising almost two-thirds of all trees, is susceptible to the nematode. [3] In the 1990s, further spread of the nematode was reported in Mexico and Nigeria.

Many factors have contributed to the global spread of the nematode, including human activities, in particular infested timber exports, as well as climate change and ecological disturbance. [3]

Morphology

Species of the genus Bursaphelenchus are difficult to distinguish because they are similar in morphology. A positive identification can be made with molecular analyses such as restriction fragment length polymorphism (RFLP). [10] [14]

B. xylophilus is distinguished by three characteristics: the spicule is flattened into a disc-shaped cucullus at the tip, the front vulval lip is flap-like, and the tail of the female is rounded. [2]

Life cycle

The pine wilt nematode has a typical nematode life cycle, with four juvenile stages and an adult stage with both male and female individuals that reproduce sexually. The mycophagous phase of the life cycle takes place in dead or dying wood, where the nematodes live and feed upon fungi, rather than the wood itself. The nematode cannot travel outside of the wood independently; it must be transported by an insect vector.

B. xylophilus has the shortest life cycle of any known parasitic nematode. In laboratory studies in which it is cultured on fungal media, its life cycle is completed in four days. In nature it reproduces most rapidly in the summer, producing large numbers of individuals that spread throughout the resin canal system of susceptible pines, into the trunk, the branches, and the roots. If living tree cells are no longer available the parasite feeds and reproduces on the fungal hyphae growing in the resin canals. While the nematode becomes inactive during the fall and winter, they survive in pine trees through overwintering. [10] [14]

Digestion

Several cellulose binding proteins are predicted by Kikuchi et al 2009. These are similar to the hosts' own expansins. [15]

Vectors

When the nematode was detected, the sawyer beetle was frequently found on dead pine trees, proving an important vector of the nematode, and that the nematode infected healthy pine trees. [16] The nematodes drop off the beetle, and infect healthy pine trees when the adult beetles eat the young pine branches. [16]

The pine wilt nematode is spread by a number of bark beetles and wood borers, typically associated with the genus Monochamus of pine sawyers. [17] Pine sawyers lay their eggs in the bark of dead timber. The growing larva feeds on the wood and pupates in the resulting cavity. Nematodes of the third juvenile stage congregate in the cavity around the pupa, molt into the fourth juvenile stage, and invade the trachea of the adult beetle. During this dispersive stage, the beetle transports the nematode to other trees. [10] [14]

Mechanism of wilt and spread

The mechanism from initial nematode infection to the resultant death of the pine tree is not fully understood. The ultimate death of the tree is caused by the nematode's inhibition of the uptake of water. Small air pockets created by the nematode lead to air embolisms in the xylem tissue which prevents water movement. [18] The embolism does not make tylose or clog the nematode or pine cell. The cause of cavitation and non-reversible embolism is not fully understood. In primary transmission, when the beetle feeds on a susceptible host pine, the pine wilt nematode enters the tree and feeds on the epithelial cells which line the resin ducts. This is referred to as the phytophagous phase of the nematode, and it results in pine wilt disease. Water transport in the tissues of the infested tree is disrupted, and the disease can manifest within as little as a few weeks. Signs include browning of the needles or yellowing of the leaves, and the tree may die within two to three months.

Grade of resistance

Furuno(1982) [19] observed standing pine trees in Japanese forest and ranked their resistance to pine wood nematode. The "high resistance" pines are rarely killed by the nematode, but young saplings or trees in weakened condition may succumb. [10] [19]

High resistance
Pinus taeda , P. elliottii, P. palustris, P. rigida, P. taiwanensis
Moderate resistance
P. strobus, P. massoniana, P. resinosa, P. tabulaeformis, P. banksiana, P. contorta, P. thumb×P. masso
Moderate susceptibility
P. bungeana, P. monticola, P. parviflora, P. strobiformis, P. densiflora, P. pinaster, P. sylvestris, P. ponderosa, P. rudis, P. pseudostrobus, P. oocarpa, P. radiata, P. greggii
High susceptibility
P. koraiensis, P. leiophylla, P. luchuensis, P. thunbergii, P. nigra, P. mugo, P. khasya, P. muricata

Ongoing initiatives in Europe

The European Commission has enacted protective measures against species harmful to plants. Specific policies targeting B. xylophilus in Portugal were enacted in 2006 before a 2012 expansion to all European Union member states. In 2015, emergency measures further expanded the definition of susceptible wood. [20]

Management in the field

In Japan, scientists and forestry officials believe the most effective preventative technique is the removal of sawyer beetles, the vector of the nematode. The sawyers like to spawn near dying or dead pine trees, so it is advised to cut down these trees until next spring. The timber is subsequently chipped, burned or sprayed with insecticide to kill the sawyer larvae and pupae in the wood. The adult sawyers go out from the timber in late spring or early summer. They start eating young pine growth and spread the nematodes to the tree. [16] Consequently, it is beneficial to kill the adult sawyers at this time to prevent the nematode infection to other trees. In Japan, organophosphorus compounds and neonicotinoids like fenitrothion, malathion, acetamiprid, and thiacloprid are typically used to treat the adult sawyers. However, many environmentalists are opposed to the use of neonicotinoid-based insecticides.

Bioinsecticides are another potential method to treat the sawyers that is currently being researched. Entomopathogenic fungus, woodpeckers, and some parasitoid or prey insects are being investigated.

Embargoes have been placed on untreated lumber from the United States and Canada to prevent the unintentional spread of this disease. Management practices have concentrated on preventing the spread of the nematode. 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 nematode has been confirmed in Portugal, and may yet spread further in Europe. [10] [11] [12] [13] [14]

In Japan, some nematocides are used to prevent the disease. For example, morantel, mesulfenfos, levamisole, emamectin, milbemectin, and thionazin. Some biopesticides are also being studied, but they remain in the experimental stage. Inoculating infected trees with nematophagous fungus may be a potential treatment for the disease. [21]

Related Research Articles

<span class="mw-page-title-main">Bark beetle</span> Subfamily of beetles

A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the term "bark beetle" refers to the fact that many species feed in the inner bark (phloem) layer of trees, the subfamily also has many species with other lifestyles, including some that bore into wood, feed in fruit and seeds, or tunnel into herbaceous plants. Well-known species are members of the type genus Scolytus, namely the European elm bark beetle S. multistriatus and the large elm bark beetle S. scolytus, which like the American elm bark beetle Hylurgopinus rufipes, transmit Dutch elm disease fungi (Ophiostoma). The mountain pine beetle Dendroctonus ponderosae, southern pine beetle Dendroctonus frontalis, and their near relatives are major pests of conifer forests in North America. A similarly aggressive species in Europe is the spruce ips Ips typographus. A tiny bark beetle, the coffee berry borer, Hypothenemus hampei is a major pest on coffee plantations around the world.

<span class="mw-page-title-main">Oak wilt</span> Plant disease

Oak wilt is a fungal disease caused by the organism Bretziella fagacearum that threatens Quercus spp. The disease is limited to the eastern half of the United States; first described in the 1940s in the Upper Mississippi River Valley. The pathogen penetrates xylem tissue, preventing water transport and causing disease symptoms. Symptoms generally consist of leaf discoloration, wilt, defoliation, and death. The disease is dispersed by insect vectors and to adjacent trees through underground root networks. However, human spread is the most consequential dispersal method. Moving firewood long distances can potentially transport diseases and invasive species.

<i>Pinus thunbergii</i> Species of conifer

Pinus thunbergii, the black pine, Japanese black pine, or Japanese pine, is a pine tree native to coastal areas of Japan and South Korea.

<span class="mw-page-title-main">Stilbenoid</span> Class of chemical compounds

Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C2–C6 structure. In biochemical terms, they belong to the family of phenylpropanoids and share most of their biosynthesis pathway with chalcones. Most stilbenoids are produced by plants, and the only known exception is the antihelminthic and antimicrobial stilbenoid, 2-isopropyl-5-[(E)-2-phenylvinyl]benzene-1,3-diol, biosynthesized by the Gram-negative bacterium Photorhabdus luminescens.

<i>Ophiostoma ulmi</i> Species of fungus

Ophiostoma ulmi is a species of fungus in the family Ophiostomataceae. It is one of the causative agents of Dutch elm disease. It was first described under the name Graphium ulmi, and later transferred to the genus Ophiostoma.

<i>Monochamus</i> Genus of beetles

Monochamus is a genus of longhorn beetles found throughout the world. They are commonly known as sawyer beetles or sawyers, as their larvae bore into dead or dying trees, especially conifers such as pines. They are the type genus of the Monochamini, a tribe in the huge long-horned beetle subfamily Lamiinae, but typically included in the Lamiini today.

<i>Bursaphelenchus</i> Genus of roundworms

Bursaphelenchus is a genus of nematodes (roundworms) in the order Aphelenchida. Most are obligate mycophages, but some feed on wood, with two species, the red ring nematode and the pine wood nematode, economically significant as pests of coconut palms and of pine trees, respectively. Given that Bursaphelenchus species are usually hard to distinguish from one another except by trained nematologists with access to microscopes or DNA sequence analysis, the entire genus is put under quarantine in some countries. Where this is not the case however, these nematodes are becoming established as model organisms for nematode developmental biology, ecology and genetics.

<i>Xyleborus glabratus</i> Species of beetle

Xyleborus glabratus, the redbay ambrosia beetle, is a type of ambrosia beetle invasive in the United States. It has been documented as the primary vector of Raffaelea lauricola, the fungus that causes laurel wilt, a disease that can kill several North American tree species in the family Lauraceae, including redbay, sassafras, and avocado.

The red ring disease of coconuts and African oil palms is caused by the nematode Bursaphelenchus cocophilus. It is also identified in literature with an alternative scientific name Rhadinaphelenchus cocophilus. The common name, the red ring nematode, is derived from its distinguishing symptom.

<span class="mw-page-title-main">Wilt disease</span> Group of plant diseases

A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi, bacteria, and nematodes can cause rapid killing of plants, large tree branches or even entire trees.

<span class="mw-page-title-main">Emamectin</span> Chemical compound

Emamectin is the 4″-deoxy-4″-methylamino derivative of abamectin, a 16-membered macrocyclic lactone produced by the fermentation of the soil actinomycete Streptomyces avermitilis. It is generally prepared as the salt with benzoic acid, emamectin benzoate, which is a white or faintly yellow powder. Emamectin is widely used in the US and Canada as an insecticide because of its chloride channel activation properties.

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<i>Fusarium circinatum</i> Species of fungus

Fusarium circinatum is a fungal plant pathogen that causes the serious disease pitch canker on pine trees and Douglas firs. The most common hosts of the pathogen include slash pine, loblolly pine, Monterey pine, Mexican weeping pine, and Douglas fir. Like other Fusarium species in the phylum Ascomycota, it is the asexual reproductive state of the fungus and has a teleomorph, Gibberella circinata.

<span class="mw-page-title-main">Lira, Salvaterra de Miño</span> Village in Galicia, Spain

Lira is a village (aldea) belonging to the O Condado shire, in Galicia, north west of Spain. Legally is one of the parishes (parroquia) under the government of the council of Salvaterra de Miño. It had 327 inhabitants in 2004 divided into 15 small villages (lugares). The patron saint of the parish is Saint Simon.

<i>Monochamus scutellatus</i> Species of beetle

Monochamus scutellatus, commonly known as the white-spotted sawyer or spruce sawyer or spruce bug, is a common wood-boring beetle found throughout North America. It is a species native to North America.

Japanese oak wilt is a fungal disease caused by Raffaelea quercivora fungus affecting by oak trees. In 1998, Japanese plant pathologists group was isolation, inoculation and reisolation the dead tree. It is the first disease known that Raffaela fungus cause plant disease.

<i>Monochamus subfasciatus</i> Species of beetle

Monochamus subfasciatus is a species of beetle in the family Cerambycidae. It was described by Henry Walter Bates in 1873. It is recorded from Japan where it infests Japanese red pine and is a vector of the nematode Bursaphelenchus doui.

<i>Monochamus alternatus</i> Species of beetle

Monochamus alternatus, the Japanese pine sawyer, is a species of beetle in the family Cerambycidae. It was described by Frederick William Hope in 1842. It is known from Hong Kong, Vietnam, Laos, North Korea, South Korea, Japan, China, and Taiwan. It feeds on Pinus banksiana, Abies firma, Pinus armandii, Pinus massoniana, Pinus yunnanensis, and Pinus densiflora. It serves as a vector for the nematode Bursaphelenchus xylophilus.

<i>Monochamus galloprovincialis</i> Species of beetle

Monochamus galloprovincialis, the pine sawyer beetle, also referred to as the black pine sawyer beetle, is a species of beetle in the family Cerambycidae. It was described by Olivier in 1795, originally under the genus Cerambyx. It has a wide distribution, occurring naturally throughout Europe and the Caucasus. It has also been introduced into the Canary Islands. It serves as a vector for the parasitic nematode species Bursaphelenchus xylophilus, and also acts as a host to the parasitoid wasp species Dolichomitus tuberculatus.

<i>Monochamus sartor urussovii</i> Subspecies of insect

Monochamus sartor urussovii is a subspecies of beetle in the family Cerambycidae. It was described by Fischer von Waldheim in 1806. It has been recorded in Eastern and Northern Europe and Northern Asia. It is a vector of the nematode Bursaphelenchus mucronatus. Larvae burrow into the wood of various conifer species and can be a tree pest, as feeding damage reduces the value of the timber.

References

  1. ↑ Bursaphelenchus xylophilus, Pine Wilt Nematode. Nematology. University of Nebraska, Lincoln.
  2. 1 2 3 Bursaphelenchus xylophilus. Archived January 4, 2012, at the Wayback Machine Nemaplex. UC Davis.
  3. 1 2 3 Proença, Diogo N.; Grass, Gregor; Morais, Paula V. (April 2017). "Understanding pine wilt disease: roles of the pine endophytic bacteria and of the bacteria carried by the disease-causing pinewood nematode". MicrobiologyOpen. 6 (2): e00415. doi:10.1002/mbo3.415. PMC   5387314 . PMID   27785885.
  4. ↑ Yano, M. (1905) 長崎県下松樹枯死原因調査. 山林公報4
  5. ↑ Steiner, G.; Burher, E.M. (1934) Aphelenchoides xylophilus, n. sp, a nematode associated with blue stain and other fungi in timber. Journal of Agriculture Research 48944951.
  6. ↑ Yozan TOKUSHIGE, and Tomoya KIYOHARA. (1969) Bursaphelenchus sp. in the wood of dead pine trees. Journal of the Japanese forestry society (日本林学会誌) 51(7): 193-195. doi : 10.11519/jjfs1953.53.7_210
  7. ↑ Tomoya KIYOHARA. and Yozan TOKUSHIGE. (1971) Inoculation experiment of a nematode, Bursaphelenchus sp., onto pine trees.　Journal of the Japanese forestry society (日本林学会誌) 53(7): 193-195. doi : 10.11519/jjfs1953.53.7_210
  8. ↑ Mamiya, Yasuharu; Kiyohara, Tomoya (1972-01-01). "Description of Bursaphelenchus Lignicolus N. Sp. (Nematoda: Aphelenchoididae) From Pine Wood and Histopathology of Nematode-Infested Trees". Nematologica. 18 (1): 120–124. doi:10.1163/187529272X00296. ISSN   0028-2596.
  9. ↑ Nickle, W. R.; Golden, A. M.; Mamiya, Y.; Wergin, W. P. (July 1981). "On the Taxonomy and Morphology of the Pine Wood Nematode, Bursaphelenchus xylophilus (Steiner & Buhrer 1934) Nickle 1970". Journal of Nematology. 13 (3): 385–392. ISSN   0022-300X. PMC   2618084 . PMID   19300780.
  10. 1 2 3 4 5 6 Dwinell, L. D. and W. R. Nickle. (1989). An Overview of the Pine Wood Nematode Ban in North America. Gen. Tech. Rep. SE-55. Asheville, North Carolina: USDA, Forest Service, Southeastern Forest Experiment Station.
  11. 1 2 Mota, Manuel M.; Vieira, Paulo C. (2008), Zhao, Bo Guang; Futai, Kazuyoshi; Sutherland, Jack R.; Takeuchi, Yuko (eds.), "Pine Wilt Disease in Portugal", Pine Wilt Disease, Tokyo: Springer Japan, pp. 33–38, doi:10.1007/978-4-431-75655-2_6, ISBN   978-4-431-75655-2 , retrieved 2022-11-08
  12. 1 2 Mota, Manuel M.; Vieira, Paulo (2008). Pine Wilt Disease: A Worldwide Threat to Forest Ecosystems. Springer Dordrecht. doi:10.1007/978-1-4020-8455-3. hdl:10174/6798. ISBN   978-1-4020-8455-3.
  13. 1 2 Suzuki, K. 2002. Pine Wilt Disease: a threat to pine forest in Europe. Dendrobiology 48, 71-74.
  14. 1 2 3 4 Forest Health Protection (2011). "Pine Wilt" (PDF). US Department of Agriculture Forest Service.
  15. ↑ Fosu-Nyarko, John; Jones, Michael G.K. (2016-08-04). "Advances in Understanding the Molecular Mechanisms of Root Lesion Nematode Host Interactions". Annual Review of Phytopathology . Annual Reviews. 54 (1): 253–278. doi: 10.1146/annurev-phyto-080615-100257 . ISSN   0066-4286. PMID   27296144.
  16. 1 2 3 Katsura MORIMOTO. and Atsushi Iwasaki(1972) Role of Monochamus alternatus as a vector of Bursaphelenchus lignicolous]. Journal of the Japanese forestry society（日本林学会誌）54(6): 177-183. doi : 10.11519/jjfs1953.54.6_177
  17. ↑ Donald, Patricia A.; Stamps, W. Terrell; Linit, Marc J.; Todd, Timothy C. (2016). "Pine Wilt". American Phytopathological Society.
  18. ↑ Kuroda, K.; Yamada, T.; Mineo, K.; Tamura, H. (1989)Effect of cavitation on the development of pine wilt disease caused by Bursaphelenchus xylophilus. 日本植物病理学会報54(5) : 606-615.
  19. 1 2 Tooshiu FURUNO. (1982) Studies on the Insect Damage upon the Pine-species imported in Japan : (No.7) On the Withering of the pines by the Pine Wilt. Bulletin of Kyoto University Forests 54, 16-30. hdl : 2433/191761
  20. ↑ "Pine Wood Nematode | European Forest Institute". efi.int. Retrieved 2022-11-08.
  21. ↑ Mamiya, Y.; Hiratsuka, M.; Murata, M. (2005) Ability of wood-decay fungi to prey on the pinewood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle. 日本線虫学会誌35(1): 21-30.
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