''Xiphinema americanum'', the American dagger nematode, is a species of plant pathogenic nematodes. It is one of many species that belongs to the genus ''

Xiphinema ''Xiphinema'' is a genus of ectoparasitic root nematodes commonly known as dagger nematodes.Whitehead, A.G. 1998. Plant Nematode Control The genus is of economic importance on grape, strawberry, hops and a few other crops. Major species include ' ...

''. It was first described by N. A. Cobb in 1913, who found it on both sides of the United States on the roots of grass, corn, and citrus trees.Cobb, N. A. (1913). "New nematode genera found inhabiting freshwater and non-brackish soils.". ;;J. Wash. Acad. Sci.;; 3: 432–435.4 Not only is ''Xiphinema americanum'' known to vector

plant virus Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants. ...

es, but also ''X. americanum'' has been referred to as "the most destructive plant parasitic nematode in America", and one of the four major nematode pests in the Southeastern United States.Christie, J. R. (1952). "Some new nematodes of critical importance to Florida growers.". ''Proc. Soil Sci. Soc. Fla.'' 30: 39Thorne, G. (1961). ''Principles of Nematology''. McGraw-Hill. New York. 553pWang, S., Gergerich, R., Wickizer, S., Kim, K. (2002). "Localization of transmissible and nontransmissible viruses in the vector nematode Xiphinema Americanum". ''Phytopathology'' 92: 646-653

Morphology and anatomy

The length of the adult ''Xiphinema americanum'' ranges from 1.3 to 3.0 millimeters. The dagger nematode is characterized by a 100 μm odontostyle which is used for deep penetration of

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the su ...

tips with its spear-like stylet. The odontostyle is connected to the lining of the cheilostome by a folded membrane called the "guiding ring". The guiding ring is attached to a flanged odontophore. Females: The body is usually in an "open C" conformation. The shape of the body tapers towards the extremities. The two rings of the odontophore are located 3 μm apart. The ''Xiphinema americanum''

esophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...

is dorylaimoid with an enlarged posterior portion that occupies roughly 1/3 of its total length. The esophagus contains a muscular bulb which is 80 μm long and 20 μm wide. The valve between the esophagus and the intestine i
amorphous
Lamberti, F.; Golden, M. (1984). "Redescription of Xiphinema americanum Cobb, 1913 with comments on its morphometric variation". ''Journal of Nematology'' 16(2): 204–206. Th
vulva
is 46-54% of the total body length, and is located equatorially with a transverse slit shape, with th
vagina
having a diameter of 1/3 of the body diameter. The

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

normally occur in pairs, and are amphidelphic and relexed. The prerectum of ''X. americanum'' measures 120–140 μm long, with
rectum
that is roughly the same length as the body diameter at the anus. The tail contains 2-3 pairs of caudal pores, is conoid, and curves dorsally with a subacute terminus. Males: The males have a similar overall configuration as the females, but are slightly smaller in length. Males of ''X. americanum'', however, are rarely found in nature. The male has diorchi
testes
that are connected to the cloaca, with one anterior branch and one posterior branch. It is common to find more coil in the posterior region. The males also have paired

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

s but lack a

gubernaculum The paired gubernacula (from Ancient Greek κυβερνάω = pilot, steer) also called the caudal genital ligament, are embryonic structures which begin as undifferentiated mesenchyme attaching to the caudal end of the gonads (testes in mal ...

and bursa.

Life cycle

Identifying ''Xiphinema americanum'' as a separate species has been a difficult task because of overlapping morphological aspects; however, differences in the life cycles of ''X. americanum'' may differentiate it from other species. Findings may also suggest that two subgroups of ''X. americanum'' should be made due to the finding of either 3 or 4 juvenile stages.Halbrendt, J. M.; Brown, D. J. F. (1992). "Morphometric evidence for three juvenile stages in some species of Xiphinema americanum sensu lato". ''Journal of Nematology'' 24: 305–309. The eggs of ''X. americanum'' are laid directly into the soil in water films, and are not associated with an egg mass. No molt occurs within the egg, which means that the first stage juvenile is the stage that enters the soil. Before becoming

sexually mature Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definiti ...

adults, the ''X. americanum'' nematodes undergo three to four juvenile stages with a

molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

occurring between each. Measurements of the functional and replacement odontostyles allows for the determination of the current stage in development.Halbrendt, J. M.; Brown, D. J. F. (1993). "Aspects of biology and development of Xiphinema americanum and related species". ''Journal of Nematology'' 25(3): 355–360. Compounding the issue of determining the life cycle of ''X. americanum'' is their difficulty with being grown in

culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups ...

or greenhouse conditions. It has been suggested that this is due to ''X. americanum's'' sensitivity to moisture tension, temperature fluctuation, physical handling, or

oxygen deprivation Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can ...

.Lownsberry, B. F.; Maggenti, A. R. (1963). "Some effects of soil temperature and soil moisture on population levels of Xiphinema americanum". ''Phytopathology'' 53: 667– 668.Griffin, G. D.; Barker, K. R. (1966). "Effects of soil temperature and moisture on survival and activity of Xiphinema americanum". ''Proceedings of the Helminthological Society of Washington'' 33: 126-130.Van Gundy, S. D.; Stolzy, L. H.; Szuszkiewicz, J. E.; Rackham, R. L. (1962). "Influence of oxygen supply on survival of plant-parasitic nematodes in soil". ''Phytopatholog''y 52: 628–632. Field evidence taken over a 2-year observation period indicates that ''X. americanum'' are most likely

k-selected In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of indivi ...

; they most likely have a long life span and a low reproduction rate.Jaffee, B. A.; Harrison, M. B.; Shaffer, R. L.; Strang, M. B. (1987). "Seasonal population fluctuations of Xiphinema americanum and Xiphinema rivesi in New York and Pennsylvania orchards". ''Journal of Nematology'' 19: 369–378. Unpublished results have shown greenhouse observations of ''X. americanum'' to develop from egg to adult in 7 months. Other results have suggested that ''X. americanum'' can live as long as 3–5 years. Reproduction by

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

from a male is rare if not nonexistent due to the lack of male ''X. americanum'' individuals, and therefore females reproduce parthenogenetically. All of the stages of ''X. americanum'' occur in the soil, with no particular stage as an important survival stage. In places with low winter temperatures, however, the egg is the primary survival structure.Griesbach, J. A.; Maggenti, A .R. (1990). "The morphometrics of Xiphinema americanum sensu lato in California". ''Revue de Nématologie'' 13: 93–103.

Host range

''X. americanum'' is a virtually non-specific plant nematode, causing it to have over one hundred different plant hosts. The most common plant hosts infected by ''X. americanum'' are common weeds and grasses, strawberries, soybeans, forest trees ( spruce,

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts ...

, etc.), perennial orchards, and

grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years a ...

s. This broad host range is due to the genetic diversity within the ''X. americanum'' species. For a complete list of the host range of ''X. americanum'' visit th
Nemaplex Host Database

Distribution

''Xiphinema americanum'' is found widely throughout most of the world and is found on all of the continents, except for Antarctica. The region with the highest population of ''X. americanum'' is thought to be the Eastern United States. The states with the highest population of the American Dagger Nematode are

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

Rhode Island Rhode Island (, like ''road'') is a state in the New England region of the Northeastern United States. It is the smallest U.S. state by area and the seventh-least populous, with slightly fewer than 1.1 million residents as of 2020, but it ...

and

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

.Robbins, R.T. (1993) "Distribution of Xiphinema americanum and Related Species in North America". ''Journal of Nematology'' 25(3):344–348. Other countries where ''X. americanum'' is found include Australia, Belize, Brazil, Chile, Guatemala, India, Japan, Korea Democratic People's Republic, Korea Republic, Mexico, New Zealand, Pakistan, Panama, South Africa, Sri Lanka, Uruguay, and areas of the Caribbean as well.Tarjan, A.C. (1969) "Variation within the Xiphinema americanum group (Nematoda: Longidoridae)". ''Nematologica'' 15, 241–252. This species of nematode is also found to be sensitive to soil pH, and they are found most frequently in soils with a pH of 6.0 or higher.Norton, D.C.; Hoffmann, J.K. (1974) "Distribution of Selected Plant Parasitic Nematodes Relative to Vegetation and Edaphic Factors". ''Journal of Nematology'' April 6(2): 81–86.

Feeding habits

''Xiphinema americanum'' is a plant parasite that lives entirely in the soil and is attracted to young, growing roots due to

source–sink dynamics Source–sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms. Since quality is likely to vary among patches of habitat, it is important to co ...

. These nematodes are migratory

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

and all of the life stages of the American Dagger Nematode feed at the root tips of plants. Since it is a migratory ectoparasite, they remain outside the root or other feeding areas and feed on

epidermal cells The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...

or on cells deeper in the root. This ectoparasitism allows the nematode to move freely to different hosts throughout its life cycle. This nematode is considered to be an obligate parasite. It can survive within plant debris, however it needs living plant tissue to feed. Once the nematode arrives at a root tip, it feeds by puncturing several successive layers of the plant's cells with its odontostyle; while penetrating, the nematode secretes

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s that result in cell

hypertrophy Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J. ...

and thickening. The nematode is then able to begin extracting the cell's

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

. The feeding period of ''X. americanum'' can last anywhere from several hours to several days, with the average being around 36 hours at each feeding site along the plant's roots. While feeding, it is common for the nematodes to remain still with their bodies either outstretched or curled, and following the feeding period they move slowly along the length of the root with their stylet remaining protruded and in search of a new feeding site. Unlike some species of nematodes, the observation of food passing into the gut of ''X. americanum'' is not seen. Although the nematodes are non-specific in their

Host Range In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

, they generally feed on plants that are in poorer condition for a shorter amount of time.Cohn, E. (1970). "Observations on the feeding and symptomology of Xiphinema longidorus on selected host roots". ''Journal of Nematology'' 2:167–173.

Symptoms and economic importance

The symptoms that plants exhibit in response to the

pathogenicity In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ge ...

of ''Xiphinema americanum'' are similar to those of other migratory ectoparasitic nematodes of roots. It is common to see poor growth and or stunting of the plant, yellowing or

wilting Wilting is the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non- lignified plant cells falls towards zero, as a result of diminished water in the cells. Wilting also serves to reduce water loss, as it ...

of the

foliage A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, s ...

, and reduced root systems which can include root necrosis, lack of feeder or secondary roots, and occasional tufts of stubby rootlets. Young, shortleaved

yellow pine In ecology and forestry, yellow pine refers to a number of conifer species that tend to grow in similar plant communities and yield similar strong wood. In the Western United States, yellow pine refers to Jeffrey pine or ponderosa pine. In the ...

trees with moderate swelling of roots with clusters of short, stubby branches were the first demonstration of ''X. americanum'' pathogenicity in 1955. ''X. americanum'' can also cause severe effects on foliage, sometimes causing

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

and complete defoliation as seen on Guatemalan

coffee tree ''Coffea'' is a genus of flowering plants in the family Rubiaceae. ''Coffea'' species are shrubs or small trees native to tropical and southern Africa and tropical Asia. The seeds of some species, called coffee beans, are used to flavor variou ...

s. The dagger nematode causes the devitalization of root tips and overall root death when they feed at the root tips and root sides of strawberry plants. Reddish-brown

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s that turn black and necrotic with time result at the sites of feeding, and result in reduced root systems and stunted tops.Perry, V. G. (1958). Parasitism of two species of dagger nematode (Xiphinema americanum and X. chambersi) to strawberry. ''Phytopathology''. 48: 420–423. ''Xiphinema americanum'' is listed as a C-rated pest in California due to its wide

host range In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

of California crops. C-rated pests are widespread, and are of known economic or environmental detriment, according t
The California Department of Food and Agriculture
Due to ''X. americanum's'' difficulty in maintaining high populations in frequently tilled soils (see

Control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

), the dagger nematode is mainly an economic problem on

biennial Biennial means (an event) lasting for two years or occurring every two years. The related term biennium is used in reference to a period of two years. In particular, it can refer to: * Biennial plant, a plant which blooms in its second year and th ...

and perennial crops rather than annual crops (except for damage to emerging seedlings).

Viral transmission

The nematode ''Xiphinema americanum'' is an important

transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...

of various plant viruses including tomato ringspot nepovirus (TomRSV), tobacco ringspot nepovirus (TRSV), peach rosette mosaic nepovirus (PRMV), and cherry rasp leaf nepovirus (CRLV).Breece, J. R., Hart, W. H. (1959). "A possible association of nematodes with the spread of peach yellow bud mosaic virus". ''Plant Disease Reporter''. 43: 989–990.Fulton, J. P. (1962). "Transmission of tobacco ringspot virus by Xiphinema americanum". ''Phytopathology''. 52: 375 (abstr.)Imle, F. P., Samson, R. W. (1937). "Studies on a ring-spot type of virus and tomato". ''Phytopathology'' 27: 132 (abstr.)Nyland, G., Lownsberry, B. F., Lowe, S. K., Mitchell, J. F. (1969). "The transmission of cherry rasp leaf virus by Xiphinema americanum". ''Phytopathology''. 59: 1111–1112 TobRSV is a widespread

nepovirus ''Nepovirus'' is a genus of viruses in the order ''Picornavirales'', in the family ''Secoviridae'', in the subfamily ''Comovirinae''. Plants serve as natural hosts. There are 40 species in this genus. Nepoviruses, unlike the other two genera (' ...

in annual crops in North America that infects tobacco, soybean, blueberry, apple, ash, autumn crocus, blackberry, cherry, dogwood, elderberry, grapevine, spearmint, and in Wisconsin has an economically important impact on

cucurbits The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in around 95 genera, of which the most important to humans are: *''Cucurbita'' – squash, pumpkin, zucchini, some gourds *''Lagena ...

.Brown, D. J. F., Halbrendt, J. M., Robbins, R. T., Vrain, T. C. (1993). "Transmission of nepoviruses by Xiphinema americanum-group nematodes". ''Journal of Nematology''. 25(3): 349–354 TomRSV is another nepovirus transmitted by ''X. americanum'', and is generally a problem with

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...

plants including apple, grapevine, raspberry, strawberry, birdsfoot-trefoil, dogwood, elderberry, hydrangeas, orchids, and red currants. It is also a problem some annual plants including tomato and cucumber. Apple, cherry, and peach trees in the Pacific coast states of the United States are infected by CRLV. PRMV causes substantial damage to ''Prunus'' spp., grapevine, and blueberry in the Great Lakes area. Much like the broad

of ''X. americanum'', the 4

es transmitted by this nematode do as well. They also have the capability of

dissemination To disseminate (from lat. ''disseminare'' "scattering seeds"), in the field of communication, is to broadcast a message to the public without direct feedback from the audience. Meaning Dissemination takes on the theory of the traditional view ...

in wind-blown seeds as well as remaining harbored in natural reservoirs including weeds. In parallel tests, TomRSV has been shown to transmit more efficiently than TRSV. Primarily, the viruses reside in the regions of the stylet extension, the anterior esophageal lumen, and rarely in the esophageal bulb. TRSV has been shown to prefer the areas of the stylet extension and anterior esophageal lumen, whereas the TomRSV is found mainly in the triradiate lumen of the esophageal bulb. The different locations of viral binding sites for TRSV and TomRSV account for the capability of dual transmission of both viruses, because the different viruses are not competing for binding sites. TRSV particles can be liberated into the plant during feeding by the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

and subventral gland secretions. TomRSV is mainly liberated by the secretions of the subventral glands due to its location in the triradiate lumen. These facts may account for the differences in the experimentally determined transformation efficiency between TomRSV (100%), and TRSV (75% or less). Previous work attempting to identify virus binding sites and release was difficult without the development of immunofluorescent labeling.

Control

Control of the American Dagger Nematode presents problems because ''X. americanum'' is hard to completely remove.

Nematicide A nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes. Nematicides have tended to be broad-spectrum toxicants possessing high volatility or other properties promoting migration through the soil. Aldicarb (Temik), a ca ...

s generally remove up to 95% of the nematodes in soil, however the 5% that remain can reproduce asexually and the viruses that they carry can still infect the roots of young plants. Therefore, to eliminate the nematodes, nematicides should be used along with having a bare soil field for at least a 2-year period. This ensures that the ''X. americanum'' has no food source. At the end of this 2-year period the nematodes should be eradicated.Halbrendt, J.M. (1996) "Allelopathy in the Management of Plant-Parasitic Nematodes". ''Journal of Nematology'' 1996 March 28(1): 8–14. The spraying of nematicides also causes plants to release allelopathic chemicals. These chemicals then kill the nematodes by active suppression because they are

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

to the nematode. Crop rotation is another form of control for ''X. americanum''. It has been shown that certain non-host plants may deny the nematode population an adequate food source for reproduction, and thus greatly reduce its population in the soil. This is termed passive suppression. ''Xiphinema americanum'' can only travel via run-off and in damp soil, therefore if soils are kept dry enough the nematodes can be localized and

quarantine A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

d.Griesbach, J. A.; Maggenti, A. R. (1989) "Vector capability of Xiphinema americanum sensu lato in California". ''Journal of Nematology'' 21, 517–523. Additionally, if soil is

tilled Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoein ...

frequently, ''X. americanum'' will likely not be in high enough of a population density to cause any noticeable symptoms in its hosts. There is also evidence of ''X. americanum'' resistance and "tolerance" seen in certain species of grapes that appeared to be better

adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

to the parasite.McKenry, M. V.; Anwar, S. A. (2006) "Nematode and grape rootstock interactions including an improved understanding of tolerance". ''Journal of Nematology'' 2006 Sep 38(3):312-8.

References

External links

Nemaplex, University of California - Xiphinema americanum
{{Taxonbar, from=Q3719816 Agricultural pest nematodes Grape pest nematodes Longidoridae Nematodes described in 1913