Tylenchorhynchus claytoni




Rev 04/03/2021

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Morphology and Anatomy Life Cycle
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Tylenchorhynchus claytoni Steiner, 1937   


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Morphology and Anatomy:




General Characteristics:

  • Length, female: 0.64-0.73 mm; length, male: 0.47-0.59 mm.

  • Body cylindroid, only weakly curved ventrally when relaxed. 

  • Cuticle about 1.5 µm thick, with coarse transverse striae about 2 µm apart, increasing to 2.9 µm on distal part of female tail. 

  • Lateral field with 4 longitudinal lines.  Apart from these, the cuticle bears 23-29 longitudinal striae, giving it a tessellated appearance.

  • Lip region rounded, offset by slight constriction, composed of 3-4 annules.  Labial sclerotization weak. 

  • Stylet slender with round basal knobs. 

  • Orifice of dorsal esophageal gland less than 2 µm behind spear base. 

  • Median bulb oval; its valve located halfway along esophagus. 

  • Isthmus long and narrow, terminal bulb pyriform, with conspicuous dorsal gland nucleus;  other gland nuclei not observed.  Esophago-intestinal valve small, hemispheroid.

  • Excretory pore opposite posterior end of isthmus.

  • Hemizonid 2 annules long, located immediately anterior to excretory pore.

  • Deirids absent.



  • Vulva a transverse slit.  Vagina less than one-half body width long. 

  • Diovarial, amphidelphic, ovaries outstretched; uteri spacious; spermathecae almost round, 10-13 µm in diameter, filled with sperm; ovaries consisting of single row of oocytes, except for a short zone near the blind end. 

  • Rectum about one-half the anal body width long.  

  • Tail tapering regularly to large, rounded, smooth terminus. 

  • Phasmids opening in anterior fourth of tail. 


  • Testis single, outstretched.  Spicules curved, with offset capitulum and acute tip.  Gubernaculum large, distinctly curved proximally.  Bursa well developed, enveloping tail, with transverse cuticular striae.

  • Terminus acute. 

  • Phasmids opening in anterior third of tail.

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 3, No. 39 (1974)]



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

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Eastern U.S.; also found in Canada, Denmark, Netherlands, and Japan.


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Economic Importance:

In the southeast US, azaleas are susceptible to damage by T. claytoni. Leaves turn yellow and plants are stunted and gradually die. They fail to respond to fertilizer and water.



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Ectoparasite on epidermal cells between root hairs in zone of  elongation.

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Turf, potato, tobacco, corn, wheat, oats, azaleas, trees in tree nurseries.  

In addition to hosts listed, Krusberg [Phytopath. 46:18    abstr. (1956)] showed that Sudan grass and Irish potato (4400 to 6400 nemas per pot) were good hosts.

Poor hosts included Crotalaria spectabilis, peanut, pepper, cucumber, and mustard (15 to 90 nemas per pot).

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

About 39 days at 24 C.  Males are common and are necessary for  reproduction.  Maximum reproduction rates occur at 90 degrees F (highest  temperature studied); range is from 65 to 90 degrees F.  From 1 to 15 eggs per day are laid 8 to 10 days after the last molt.  The first molt occurs  inside the egg. 

   The sexes can be recognized in the third juvenile stage by the gonad  primordium. 

Nematode can survive at least 10 months in the absence of a host.    

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Causes damage to young corn in North Carolina [Nelson, 1956], but older plants can tolerate larger populations; lines were selected which  were resistant to T. claytoni.  Evidence from pot culture indicates changes in size and shape of nuclei in corn roots.

In the 1950s, Graham   reported 67% of 175 collections in tobacco fields in South Carolina were infested and plants stunted.  Pathogenicity tests positive on tobacco  roots stunted; no lesions.  Results were confirmed in pot tests, but  researchers used small pots which may have caused additional plant stress [Phytopath. 46: 12-13 (1954)]. 

Mountain [Can. J. Bot. 32:737-759 (1954)] in Canada observed T. claytoni attacking wheat and oats, but not tobacco. 

In Wisconsin and California, this species was found to injure azaleas [Sher, PDR].


Slash pine seedlings stunted by T. claytoni (on left), healthy seedling on right.
From Hodges, (1962)
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Nematicides are effective; ethylene dibromide (EDB) was better than D-D mixture for control. 

DBCP, 1,3-Dichloropropene (1,3-D), and Aldicarb have also been used for control.

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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 CIH Descriptions of Plant-parasitic Nematodes, Set 3, No. 39 (1974)

Hodges, C.S. 1962. Diseases in southeastern forest nurseries and their control. Station Paper 142./

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Copyright © 1999 by Howard Ferris.
Revised: April 03, 2021.