Helicotylenchus dihystera

 

Contents

 

Rev 12/27/13

  Classification Hosts
Morphology and Anatomy Life Cycle
Return to Helicotylenchus Menu Economic Importance Damage
Distribution Management
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Classification:

       Tylenchina
        Tylenchoidea  
         Hoplolaimidae
          Hoplolaiminae
           Helicotylenchus dihystera (Cobb, 1893) Sher, 1961

    Synonyms:
   Tylenchus dihystera Cobb, 1893
   Tylenchus olaae Cobb, 1906
   Tylenchus spiralis Cassidy, 1930
   Aphelenchus dubius var. peruensis Steiner, 1920
     Helicotylenchus nannus Steiner, 1945
     Helicotylenchus crenatus Das, 1960
   Helicotylenchus punicae Swarup & Sethi, 1968

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Morphology and Anatomy:

  Female: Length: 0.61-0.86 mm (0.67 mm average).

Body spiral, more so posteriorly; striae distinct.

Lip region hemispherical, with 4 or 5 annules; outer margins of labial framework conspicuous, extending 2-3 annules into body.

Anterior cephalids 3-4 annules behind lip region; posterior cephalids indistinct, 5-7 annules behind the anterior ones.

Lateral fields one-fourth to one-third body width, with 4 incisures, not areolated.

Spear well developed; anterior tapering part 11.0-12.5 m long; basal knobs about 4.5 m across by 2.5 m high, with concave or indented anterior surfaces. Spear guide prominent, apparently providing attachment surfaces for the protracter muscles of the spear.

Orifice of dorsal esophageal gland at less than half spear length behind spear base.

Median esophageal bulb oval, 6-8 body annules long.

Excretory pore usually near esophago-intestinal junction, 0-2 annules behind the 2-3 annules long hemizonid.

Hemizonion indistinct.

Esophageal glands partially surrounding anterior end of intestine; subventrals slightly longer than the dorsal.

Ovaries paired, outstretched, with oocytes mostly in single file.

Epiptygma not seen. 

Tricolumella distinct with 12 cells in 3 rows. Spermathecae offset, without sperms.

Tail dorsally convex-conoid to a narrow terminus which may form a slight projection, with 8-12 annules ventrally; phasmids 6-12 annules in front anus, usually centrally placed in the lateral fields; inner incisures on tail usually not fusing distally for some distance.

Males: Similar to female except for non-spiral body shape and sexual dimorphism. Extremely rare and not essential for reproduction.

Stylet 22-27 m, spicule 22-23 m, and gubernaculum 7-8 m.

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 1, No. 9 (1972)]

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Distribution:

 

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Economic Importance:

D-rated pests in California.

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Feeding:

Ecto- and semi-endoparasites; have large population densities.

Nematode causes small, brown lesions on soybean roots (6-10 cells around head).

The walls of the infected cells and those adjacent were lignified, but there was no indication of nuclear proliferation, giant-cell formation, or swelling. Churchill & Ruehle (1971) observed that H. dihystera penetrated fibrous roots of greenhouse grown sycamore behind their tips and at the intersection of lateral and branch roots where they were found completely embedded in the cortical tissue, but in other root sections, they were only partially embedded.

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Hosts:

Sugarcane, rice, potatoes, corn, peanut, millet, sorghum, forest trees, and banana.

For an extensive list of host plant species and their susceptibility, copy the name

Helicotylenchus dihystera

select Nemabase and paste the name in the Genus and species box

 

 

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Life Cycle:

Nematode reproduces by parthenogenesis; there is no indication of sperm in the spermatheca

The first molt takes place within the eggs, and the three larval stages occurring outside the egg can be recognized by the development of the reproductive system. 

H. dihystera survived for 6 months in soil stored in plastic bags, both at room temperature and in the refrigerator at 1.1-1.4 C (Ferris, 1960).  In field and laboratory studies, H. dihystera entered an anhydrobiotic state; nematode numbers were higher after soil desiccation during the dry season than for H. multicinctus (Baujard and Martiny, 1995).

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Damage:

Reduced root growth and top weight; 78% reduction in growth of olive seedlings in Egypt observed over 6 month period with nematode populations of 1,000 individuals per pot.

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Management:

Peeled banana corm dipped in DBCP (Peachey and Hooper, 1963) promoted heatlhy plant growth. 

Crop rotation schemes can be effective, in some cases.

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

For a list of plant species or cultivars (if any) reported to be immune or to have some level of resistance to this nematode species, copy the name

Helicotylenchus dihystera

select Nemabase Resistance Search and paste the name in the Genus and species box

 

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References:

 Baujard, P. and B. Martiny.  1995.  Ecology and pathogenicity of the Hoplolaimidae (Nemata) from the sahelian zone of West Africa: 7. Helicotylenchus dihystera (Cobb, 1893) Sher, 1961 and comparison with Helicotylenchus multicinctus (Cobb, 1893) Golden, 1956. Fundamental and Applied Nematology 18: 503-511.

CIH Descriptions of Plant-parasitic Nematodes, Set 1, No. 9 (1972)]

CIH Descriptions of Plant-parasitic Nematodes, Set 2, No. 23 (1973)

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Copyright 1999 by Howard Ferris.
Revised: December 27, 2013.