Paratylenchus hamatus




Rev 02/13/2023

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           Paratylenchus hamatus Thorne and Allen, 1950

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Morphology and Anatomy:


Paratylenchu hamatus
From Thorne and Allen (1950).  mb = membrane(or advulval flap)  lateral to vulva. Note small, hooked sheath around protruded spicules.
Small plant-parasitic nematodes, 0.3mm long. 
Cuticle marked with fairly coarse striae.
Lip region continuous with body contour.
Four incisures in lateral field.

Females:  Gravid female may swell anterior to vulva.

Strong stylet, usually about 36 µm.

Ovary single, prodelphic, outstretched. 

Vulva a transverse slit with lateral membranes which may extend inward over the vulval opening.  In other literature these are referred to as advulval flaps (Ghaderi et al., 2014).  


Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:


Males:  Stylet moderately developed and median bulb appearing weak.
Spicules elongate arcuate, resting in a thin, trough-like gubernaculum.  When protruded, the spicules are surrounded by a short sheath, with a posterior hook-like process, protruding from the cloacal opening.  The specific name hamatus is derived from the presence of the hook like process.

Ref: Thorne and Allen, 1950.
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Europe and North America.

Widely distributed in California, but not usually found in cooler grape-growing regions.

Originally described from fig in soil samples taken by E.F. Serr near Planada, California (11 miles west of Merced) and sent to Gerald Thorne in Salt Lake City for diagnosis.  From those samples, Thorne and Allen (1950) described both Xiphinema index and Paratylenchus hamatus.

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Economic Importance:

Paratylenchus hamatus is apparently the most common species of pin nematode in woody perennials of California (Raski, 1975). 

It can occur in abundance in vineyards free of other vegetation, but it is not associated with vine damage except when young grapevines have been planted into very high population levels. 

Highest population levels of this nematode are often measured on the most vigorous vines and its presence appears to slow the build-up of other endo- and ectoparasites (Ferris and McKenry, 1975; Ferris et al., 1976). 

Feeding of large numbers produced shallow, localized lesions on grape roots (Raski and Radewald, 1958).

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Celery, figs, grapes, and peaches in the San Joaquin Valley of California. 

It does not occur on Juglans spp.

For an extensive host range list for this species, click


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Life Cycle:

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click If species level data are not available, click for genus level parameters


Similar to P. neoamblycephalus, but has a different host range and there are differences in the life cycle of the male. 

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Associated with crop decline in figs (Thorne and Allen, 1950), but a positive correlation with vigor has been observed in grape and peach (Ferris and McKenry). McKenry has suggested that P.hamatus may have  an antagonistic or competitive relationship with Mesocriconema xenoplax - in field experiments (1998-90) soil around peach roots was inoculated with P. hamatus after fumigation, but results were not convincing. 

This nematode also causes damage to celery in North Eastern U.S. and the Netherlands; can also deform carrots. 

Plant weights of mint may be reduced and flowering delayed by P. hamatus infestation in the Yakima Valley of Washington (Ingham and Merrifield, 1996).

In pot experiments, dry weights of peppermint and scotch spearmint plants 22 weeks after inoculation were reduced 20%-34%.  Infected plants remain succulent longer which renders them susceptible to winter injury (Faulkner, 1964).

In tall fescue grass, tillering was increased but top growth is stunted (Coursen and Jenkins, 1958).

Tops of celery attacked by pin nematodes can become stunted and chlorotic  (Lownsbery et al., 1952). Figs infected by pin nematodes become chlorotic with undersized fruit (Thorne and Allen, 1950).  


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Host Plant Resistance, Non-hosts and Crop Rotation alternatives:

For plants reported to have some level of resistance to this species, click
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Coursen, B.W. and W.R. Jenkins. 1958. Host-parasite relationships of the pin nematode, Paratylenchus projectus on tobacco and tall fescue. Plant Disease Reporter 42:865-872.

Faulkner, L.R. 1964. Pathogenicity and population dynamics of Paratylenchus hamatus on Mentha species. Phytopathology 54:344-348.

Ferris and McKenry, 1975

Ferris et al., 1976 

Ghaderi, R., Kashi, L., Karegar, A. 2014. Contribution to the study of the genus Paratylenchus Micoletzky, 1922 sensu lato (Nematoda: Tylenchulidae). Zootaxa 3841(2):151–187.

Ingham, R., Merrifield, K. 1996. A Guide to Nematode Biology and Management in Mint. Integrated Plant Protection Center, Oregon State University, Corvallis. Pub. No. 996. 38 p.

Lowensbry, B.F., E.M. Stoddars and J.W. Lownsbery. 1952. Paratylenchus hamatus pathogenic on celery. Phytopathology 42:651-653.

Raski, D.J. 1975. Revision of the Genus Paratylenchus Micoletzky, 1922 and Descriptions of New Species. Part II of Three parts. J. Nematology 7 :274-295.

Raski, D.J., Radewald, J.D. 1958. Symptomology of certain ectoparasitic nematodes on roots of Thompson seedless grape. Plant Disease Reporter 42:941-943.

Thorne, G. and M.W. Allen. (1950)  Paratylenchus hamatus n. sp. and Xiphinema index n.sp., two nematodes associated with fig roots, and a note on Paratylenchus anceps.  Proc. Helminth. Soc. Wash 17:27-35.

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Copyright © 1999 by Howard Ferris.
Revised: February 13, 2023.