Ogma rhombosquamatus

 

Contents

  

Rev 04/05/2021

  Classification Hosts
Morphology and Anatomy Life Cycle
Return to Ogma Menu Economic Importance Damage
Distribution Management
Return to Criconematidae Menu Feeding  References
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Classification:

      Tylenchida
       Tylenchina
        Criconematoidea
         Criconematidae
          Criconematinae


          Ogma rhombosquamatus (Mehta & Raski,1971) Andrassy, 1979

      Synonyms

  

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Morphology and Anatomy:

 Females:
  • Two head annules with irregular crenate edges and fine incisures along the annule edges  The first annule is anteriorly directed.
  • Amphidial apertures rectangular.
  • Scales on body annules appear semidome shaped viewed by SEM but diamond shaped under light microscope.
  • Longitudinal grooves between scales have transverse ridges.
  • Vulval lips protrude slightly from the body sur[ace, and the anterior lip is marked by three protuberances along the edge. The posterior lip is regular, with smooth edge.
  • Anal aperture is located between two ventral scales on the 9th (8-10) annule.
  • Terminal annule is small, conoid, and spiralled.


    • Males:
  • Lack stylets and do not feed.
  • Annules coarse.
  • Lateral field with two longitudinal striae.
  • Lip region rounded.
  • Oesophagus and intestine degenerate.
  • Hemizonid distinct, 2-3 annules long and 5-6 annules anterior to excretory pore.
  • Testis single, outstretched, and occupying about 40% of body length.
  • Spicules arcuate, cephalated, and finely pointed.
  • Gubernaculum linear and slightly curved.
  • Caudal alae (observed in only 60% of specimens) rudimentary with distinct annulate margin, extending from just behind the cloacal opening to 2-3 annules before terminus.
  • Body narrowing posterior to cloaca; tail conical with regular distinct annules and pointed terminus.
Ref: Vovlas and Inserra (1981).

 

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

Originally reported from Pinus sp. and Smilax sp. in northern Italy.  Later found on olive in volcanic sands and sandy loam soils in Italy and Sicily (Vovlas and Inserra, 1981).

 

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Economic Importance:

 

 

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Feeding:

Ogma rhombosquamatus was observed feeding as an ectoparasite on feedr roots of olive trees. Females aggregate at feeding sites with eggs adhering to the root surface and among root hairs. No gelatinous matrix observed.

Females remained attached to the root surface by the stylet which penetrated the epidermis and 2-3 layers of cortical cells.

Nematode feeding activity induced thickening of cortical cell walls and hypertrophy of the nucleus and nucleolus to a size 4-5 times larger than those of normal cortical cells. Necrosis was observed in epidermal and cortical tissue.

Males which lack stylets were not observed on roots. (Vovlas and Inserra, 1981).

 

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Hosts:

 

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

 

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Damage:

 

 

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Management:

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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References:

Vovlas, N., Inserra, R.N., 1981 Parasitic Habits of Ogma rhombosquamatus and Description of the Male. J. Nematology 13:87-90.

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Copyright © 1999 by Howard Ferris.
Revised: April 05, 2021.