Tylenchorhynchus annulatus




Rev 04/03/2021

Stunt Nematode  Classification Hosts
Morphology and Anatomy Life Cycle
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Tylenchorhynchus annulatus (Cassidy, 1930) Golden, 1971 

      Tylopharynx annulatus Cassidy, 1930
      Anguillulina annulata (Cassidy, 1930) Goodey, 1932
      Chitinotylenchus annulatus (Cassidy, 1930) Filipjev, 1936
     Tylenchorhynchus martini Fielding, 1956

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Morphology and Anatomy:

Length, female: 0.66-0.72 mm long.  T. annulatus = (T. martini)

Female: Body ventrally arcuate; cuticle moderately thick, distinctly annulated by deep striae 1.7-1.9 µm apart near midbody; no longitudinal striae.

Lateral fields 0.30-0.35 times body width, with 4 incisures making  3 almost equally wide longitudinal bands; outer incisures crenate; outer bands irregularly areolated in places. 

Deirids absent.

Phasmids distinct,  pore-like, 13-17 µm or 7-8 annules behind anus, anterior to middle of tail. 

Lip region rounded, slightly marked off from body by increased width, with 3 transverse striae (occasionally 2); 7.0-7.5 µm wide and 4 µm high; framework lightly sclerotized with outer margins extending 2 to 3 annules into body. 

Stylet is 17-18 µm long, in two almost equal parts, anterior conical part solid, needle-like in distal half, posterior part with distinct, rounded basal knobs, about 3 µm across and with flattened to convex anterior surfaces. 

Orifice of dorsal esophageal gland 1.5-2 µm from stylet base, rather obscure. 

Median esophageal bulb oval, occupying 6 to 7 body annules, with oval valve near center. 

Basal esophageal bulb sac-like, with a large cardia pushing into its base slightly ventrally; nucleus of dorsal gland conspicuous, in posterior half of bulb; nuclei of subventral glands inconspicuous, about middle of bulb.

Nerve ring at middle of isthmus

Excretory pore 52-59 annules behind lip region, opposite base of isthmus

Hemizonid prominent, 2 body annules long, just in front of excretory pore

Intestine with fasciculi (serpentine canals) and scattered granules.

Rectum shorter than anal body width, partially overlapped by intestine; anus distinct. 

Tail elongate sub-cylindrical, 3.1-3.6 times anal body width long, almost straight to slightly arcuate ventrally, with 18-22 annules ventrally and a broadly round, unstriated terminus. 

Vulva transverse; vagina straight, extending half-way into body. 

Spermatheca absent. 

Ovaries paired, outstretched, opposed, with a single row of oocytes.

Male: absent.  Not found among 80,000 specimens examined by Fielding  (1956).

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 6, No. 85 (1976)]

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

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Tropical and subtropical areas; e.g., India, parts of Africa, Venezuela, Hawaii, Louisiana, Texas, Florida, and Georgia.


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Economic Importance:



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Migratory ectoparasite.

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Sugarcane, rice, sorghum, sweet potato, soybeans, red clover, cotton, ornamentals, and grasses.  Potato is a less-favorable host.

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

On oat and wheat seedlings, T. annulatus multiplies more rapidly at higher soil temperatures (30 C) than at lower temperatures (18 and 24 C).

Nematodes are capable of withstanding a wide variation of soil temperature extremes. 

Soil-type has no apparent influence on population growth.

Swarming: The phenomenon of swarming was reported by Hollis (1958); swarming has also been observed in other nematodes, e.g., RotylenchulusHemicycliophora, Aphelenchus, Heterorhabditis, especially in drying conditions.  Hollis felt swarming was initiated by rapid growth of host plant and nematodes kept together by stickiness of outer cuticle. 

Stickiness and swarming are inhibited by pectidase enzymes.  If food is less available, nematodes revert to a non-swarming state. 

Hollis considered swarming a virus disease, and claimed virus particles might be infecting somatic muscles and hypodermis, but this has not been confirmed.

No other virus diseases of nematodes are known.

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Nematode is pathogenic to sugarcane in Louisiana; in studies, inoculated plants had more sparse, irregular, and stubby roots than the control. 

Hollis et al. (1959) and Hollis (1967) concluded that, although slight reduction of growth of rice seedlings was demonstrated with high population levels, this nematode was not pathogenic to rice. 

Other researchers have observed that both swarming and non-swarming nematodes of this species can cause significant reductions in root length and root dry  weights of the rice cultivars Saturn and Zenith, but swarmers accounted for a greater reduction than the non-swarmers, and caused severe stunting and chlorosis of the plants (Joshi & Hollis, 1976). 

Johnson (1970) reports that this species feeds on roots of Bermuda grass (Cynodon dactylon) ectoparasitically, usually on the young, succulent roots.  The root damage results from feeding involving cell destruction, injection of digestive secretions, and removal of cellular contents; feeding on lateral roots results in root-pruning, decreased water and mineral uptake, and depressed plant growth; feeding on root-tips causes severe stunting and  necrosis.

 [Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 6, No. 85 (1976)]

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Soil fumigation for rice and sugarcane recommended in Texas and Louisiana.
Most sugarcane varieties used in breeding programs show very little or no resistance to infection by T. annulatus.  Control of weed hosts is  important, e.g., Johnson grass. 

No satisfactory crop rotation management strategies exist (but rotation to rice may be effective in preventing damage to sugarcane in Louisiana).

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