(Steiner & Buhrer, 1934) Nickle, 1970
Originally described as Aphelenchoides xylophilus by
Steiner and Buhrer in 1934 from blue-stained logs of Pinus
palustris at a sawmill in Bogalusa, Louisiana.
Male: Shape of spicules
and caudal alae at tail tip are characteristic of genus.
The male tail is curved
ventrally, conoid and has a pointed terminus. The spicules are
well developed, with a prominent rostrum and are flattened into a
disc-like cucullus at the distal end.
B. xylophilus has the general characteristics of
Bursaphelenchus spp.: lips high and offset; weak stylet with small
knobs; median bulb well developed; dorsal esophageal gland opening
inside the median bulb.
B. xylophilus can be distinguished by the
simultaneous presence of three characters: The spicules are flattened
into a disc-like structure (the cucullus) at the distal end. The
anterior vulval lip is a distinct overlapping flap and the posterior end
of the female body is rounded in nearly all individuals ( this character
separates B. xylophilus from B. mucronatus, a
non-pathogenic species in which the female has a mucronate tail).
However, it is difficult to differentiate between B. mucronatus
and populations of B. xylophilus in North America that have
mucronate tails. (EPPO Bulletin).
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Bursaphelenchus xylophilus was first described in, and is perhaps
native to, North America. The
nematode occurs in 36 states in the U.S., including all the Great Plains states
with the exception of North Dakota; almost all prefectures in Japan,
several provinces in China. It also occurs in Canada, Mexico, Taiwan, Korea, and
This and related species are vectored by cerambycid longhorn
beetles, also known as sawyers, of the genus Monochamus. Several
species of Bursaphelenchus have a
phoretic relationship with
Monochamus spp., which carry them to recently felled logs and dead or dying
conifers, particularly pines. Monochamus, Bursaphelenchus, or both
may be found in pine chips, unseasoned lumber, and logs. Consequently, it is
easily transported in wood products, such as logs, lumber, pallets, crates, wood
chips, and furniture, that are not kiln-dried.
The beetles are wood borers in the larval stage (Linit,1987). M.
alternatus is the primary vector in Japan and China, but there are
others. Monochamus galloprovincialis is considered an important vector
in Europe (Abelleira et al., 2020)
When introduced into Japan and other Asian countries, B. xylophilus
became a destructive pest of pines. Countries in the European Union and
elsewhere regulate the import of all coniferous chips, sawn wood, and logs (Dwinell,
The nematode can also be vectored by the pine sawyer beetle to a dying tree or freshly cut timber
during the female beetle's oviposition or egg-laying. This is the more likely
transmission pathway in North America, where the pinewood nematode is thought to
be native. The nematode can also feed on fungi growing in dying or dead trees or
in cut timber and thus can be
Monochamus spp. (Cerambycidae)
Adults: Family characteristics of antennae, eyes and tarsi + generic
characteristics of elongate cylindroidal form, prothorax with small conical
projections from side, antennae very long, second segment very small.
Grubholes elliptical, frass-filled, adult exit holes circular.
Initial stage of attack shows as irregular channeling of wood surface.
Larvae may tunnel more than one year before pupation.
Species of Pinus,
Larval boring causes extensive damage to dying, recently dead and
felled conifers. In China and Japan, M. alternatus is the vector
for pinewood nematode.
(excerpt from Pine Wilt in Japan - Ministry of Agriculture, Forestry
and Fisheries, Japan)
pest in California Nematode Pest
The causal agent ov Pine Wilt Disease which has been devastating to forests
in East Asia and in some areas of Western Europe.
The annual loss of pine timber in Japan was 2.4 million cubic
meters by the 1970s.
The nematode is reported from 36 states in the U.S. but may cause little direct damage.
It has major economic consequences in that Scandinavian and other
countries have established embargoes on wood and wood chips (e.g.
for paper pulp) from inmfested areas and when nematodes are detecte4d during
phytosanitary inspection. Samples from shipments suggest population
increases in wood chips during voyage.
Economic analysis of Bursaphelenchus xylophilus
as an invasive species in Europe (Soliman et al., 2012):
Nematodes spread through axial and radial resin canals of pine
trees, feeding on epithelial cells.
Sexually reproducing. Insect vectors include several beetles,
Detailed studies on the mating behavior of B. xyopihilus (Liu et
al., 2014) documented a series of sub-behaviors in the mating process:
The probability of male:female contacts ot female:J4
within 1 hour was 100%, 90% for male:j4 but only 30% for female:female
contact, 70% for male:male contact. Male head movement frequency increase
significantly when introduced into water previously occupied by a female,
indicating that females produce sex-attractant pheromones.
larvae are carried most frequently by Pine Sawyer beetles (M.
alternatus) in Japan and by related species in the U.S.
In a damaged pine forest in Japan, >75% of Pine Sawyer
adults had dauer larvae, averaging 15,000/insect, with a maximum
Insect lays eggs in bark of weakened tree; larvae hatch after
1 week; larvae burrow into wood and molt, creating a U-shaped
tunnel back toward surface ending in pupal chamber.
(excerpt from Pine Wilt in Japan - Ministry of Agriculture,
Forestry and Fisheries, Japan)
In the early stages of an infection the nematodes disperse through resin
canals in the tree cortex and xylem of Pinus species; they multiply in
the inner bark and xylem tissues.
Nematode development requires 5 days to adult, followed by 28
days of oviposition of 80 eggs per day. With unlimited resources
a single female could give rise to 260,000 offspring in 15 days.
Ther resting stage of nematode, the 4th stage dauer larva, appears
at high population densities. The dauer larva survives dry
conditions, lack of food, cold, etc. - thicker cuticle, denser
body contents. It is also the dispersal stage. The dauer larvae
enter the pupae of the insect through spiracles and up to 100,000
are carried in the tracheae.
(Life cycle diagram from University of Vermont)
Bursaphelenchus xylophilus is readily cultured in lab on Botrytis cinerea
and other fungi.
Pine tree death, Kansas
Trees already infected decline, thus attracting more insects
to weakened trees for oviposition. A new generation of insects
then becomes infected in the diseased trees. Drought and other
stress may hasten the decline of trees. Damage due to pine wilt
nematode has often been attributed to fungi, insects, etc.
Nematodes can be present in dead or living wood, and Wingfield
points out that presence does not indicate that it killed the
tree as it is primarily a fungus feeder. However, direct
inoculation of the nematode into trees in Japan killed 100% of
Tree death occurs within in 1 year in Japan.
Pine Wilt Disease: Resin flow stops 2 weeks after inoculation; transpiration is
depressed; trees wilt; sapwood desiccates; foliage turns brown;
tree dies 45 days later.
Dr. Mamiya reported (SON, 1987) that the nematode was found at
only one location in Japan prior to 1930s, spread to 34
prefectures through the 1940s, and to 45 of the 47 prefectures by
the 1970s. Thought to have been introduced into pine in Japan
from elsewhere; pine species in Japan are very susceptible to
Pine Wilt disease.
Pine forests are still healthy in cooler regions of northern
Japan, so large efforts are being undertaken to prevent spread.
In North America, native conifers are mostly resistant or tolerant to
B. xylophilus, and it causes little damage than on exotic pine species
(Mamiya, 1983; Kiyohara and Tokushige, 1971).
A male-produced aggregation pheromone provides opportunities for trapping and
otherwise managing the vector (Teale et al., 2011; Fierke et al., 2012):
Adults of both sexes of
M. alternatus are attracted to lires
consisting of to 2-(undecyloxy)-ethanol (monochamol), the male-produced
pheromone of the congeneric M. galloprovincialis, combined with
the host plant volatiles alpha-pinene and ethanol. The combination of 2-
(undecyloxy) -ethanol with ethanol and/or alpha-pinene will provides
opportunities for quarantine detection, monitoring, and management of
Monochamol (2-(undecyloxy)-ethanol) is also produced by
males of Monochamus scutellatus scutellatus which is
native to North America. A congener, Monochamus notatus, which
uses the same hosts as M. s. scutellatus, also is attracted to
this compound, suggesting that it is effective with several species. In
panel traps at each of five field sites, around 170 adult M.
s. scutellatus and 15 M. notatus were captured, in a
ratios of 3:1 females:males. Interestingly, analysis of headspace
volatiles indicate that in M. s. scutellatus monochamol is
produced only by males and is not produced by M. notatus, which
nevertheless responded to the attractant. The study provides
further evidence that monochamol is a pheromone component common to
several species in the genus Monochamus.
Control insect vectors with insecticides; burn infected trees.
Trunk injection of nematicides has been used in Japan,
especially for valuable trees in parks, etc., but must be
performed before symptoms occur. The technique has also been
tested in Portugal.
Breeding resistant trees a promising approach. Species of pine
vary in their resistance. Populations of the nematode differ in
host preference, and response of pines differs.
Host Plant Resistance, Non-hosts
Tree genera and species in the Pinaceae differ in their host status and
tolerance to the nematode.. The presence of the nematode in wood of dead
trees does not necessarilty indicate susceptibility because, besides Pinus,
Monochamus spp. beetles use species of the genera Abies, Cedrus,
Larix and Pices for feeding and reproduction. Consequently,
transfer to nonhosts can occur. When young trees of Abies sachalinensis
(Sakhalin Fir) an Picea jezoensis (Jezo Spruce) were inoculated with
the nematode, respectively 20% and 10% of the trees were killed. In
contrast, mortality was 40% and 70%, respectively, in P. densiflora and
P. thunbergii. Reproduction of the nematode in A.
sachalinensis and P. jezoensis was only about 10% of
that in P. densiflora and
P. thunbergii after 12 weeks of incubation in stem sections (Kasuga and
Togashi (2012) indicating differences in host status and tolerance to damage.
Tolerance of selectionms made from the susceptible species
Pinus densiflora and P. thunbergii:
Tolerant trees are selected from
P. densiflora and P.
thunbergiithat have survived pine
wilt disease.Selected trees are divided into tolerance classes based on
their response yo a virulent isolate of B. xylophilus. Seedlings of trees
belonging to tolerant clones have been used for reforestation in Japan. The
tolerance mechanism is is thought to be a high oncentration of tannin or a
low pH of sap in the inner bark (Menï¿½ndez-Gutiï¿½rrez
ey al., 2017).
Procedures to disinfest transported unprocessed wood include prevention, host
selection, and treatment by fumigation, irradiation, chemical dips, and elevated
temperatures. (Dwinell, 1997)
CABI . Data Sheets on Quarantine Pests: Bursaphelenchus
Dwinell, L.D. 1997. Annual Review of Phytopathology
Fierke, M.K., Skabeikis, D.D., Millar, J.G., Teale, S.A., Mcelfresh,
J.S., and Hanks, L.M.. 2012. Identification of a male-produced
aggregation pheromone for Monochamus scutellatus scutellatus and
an attractant for the congener Monochamus notatus (Coleoptera:
Cerambycidae). Journal of Economic Entomology 105:2029-2034.
Kasuga H and Togashi, K. 2012. Nine-month persistence of
Bursaphelenchus xylophilus in living Abies sachalinensis and Picea
jezoensis seedlings and nematode reproduction in stem sections.
Kiyohara, T. and Tokushige, Y., 1971. Inoculation experiments of a
nematode, Bursaphelenchus sp., onto pine trees. Journal of the Japanese
Forestry Society, 53(7), pp.210-218.
Liu, B.-J., Hu, J.-F., Liu, Z.-Y., Xu, L., Lu, Q., Li, Y.-X., and
Zhang, X.-Y. 2014. Behavioural features of Bursaphelenchus
xylophilus in the mating process. Nematology 16:895-902.
Mamiya, Y. 1983. Pathology of the pine wilt disease caused by Bursaphelenchus
xylophilus. Annu. Rev. Phytopathol. 21, 201ï¿½220
K. Matsunaga and K.
Relationship between pine wilt-tolerance rankings of Pinus
and the number of Bursaphelenchus
xylophilus passing through
sections. Nematology 19:1083-1093.
Mota, M. and P. Viera. 2004. The pinewood nematode,
xylophilus : proceedings of an international workshop, University of
Portugal, August 20-22, 2001.
Nematology monographs and perspectives ;v. 1. Brill, Leiden.
Movie: Pine Wilt Nematode. Japanese Forestry Agency,
Ministry of Agriculture, Forestry and Fisheries, Japan.
Scheck, H. J. 2021. California Pest Rating Proposal for
Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) Nickle, 1970. CDFA website.
Soliman, T., Mounts, M.C.M., van der Werf, W., Hengeveld, C.,
Robinet, C., Oude Lasink. A.G.J.M. 2012. Framework for modelling economic
impacts of invasive species, applied to Pine Wood Nematode in Europe.
Plos One 7: e45505.
Teale SA, Wickham JD, Zhang F, Su J, Chen Y, Xiao W, Hanks LM, Millar JG.
2011. A male-produced aggregation pheromone of Monochamus alternatus
(Coleoptera: Cerambycidae), a major vector of pine wood nematode. Journal of
Economic Entomology 104:1592-1598.