Hirschmanniella oryzae

 

Contents

 

Rev 10/07/2024

 Rice Root Nematode Classification Hosts
Morphology and Anatomy Life Cycle

Return to Hirschmanniella Menu

Economic Importance Damage
Distribution Management
Return to Pratylenchidae Menu Feeding  References
    Go to Nemaplex Main Menu   Go to Dictionary of Terminology

Classification:

       Tylenchina
        Tylenchoidea
         Pratylenchidae
          Pratylenchinae
           Hirschmanniella oryzae (Van Breda de Haan, 1902) Luc & Goodey, 1964

 

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Morphology and Anatomy:

 
  • Nematode around 2 mm long. 

  • Long overlap of esophagus over intestine.

  • Diovarial females, sexually reproducing. 

  • Typical pratylenchid stylet.

  • Nematodes are unusually long for endoparasites, but inhabit air channels rather than an intracellular environment.

 

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

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Distribution:

Hirschmanniella oryzae  is found throughout rice-growing regions, Asia, Japan, West Africa, South America, U.S. in Texas and Louisiana; but is thought not to be present in California.  Sher found complexes of several species in collections from rice, including H. spinicaudata and H. belli.  Literature prior to 1968 may deal with mixtures.

Zheng (in Davis as a visiting Chinese scholar in the early 1980s), surveyed 100 rice fields around Northern California and concluded all the Hirschmanniella populations that he found were H. belli.  He concluded that populations of H. belli  in California were much lower than those of  H. oryzae in China.  The nematodes identified as H. belli are  commonly associated with sedges and common cattail (Typha latifolia) along streams and in wet ditches surrounding rice fields. It should be noted that the Zheng and other studies were based on morphometric and anatomical characters of the nematodes and did not employ molecular techniques.

 

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Economic Importance:

A-rated pest in California Nematode Pest Rating System.

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Feeding:

Migratory endoparasite of roots.  Juveniles and adults enter behind the root tip and move in air channels; can also migrate into older roots. 

Nematodes do not migrate up into stem.

 

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Hosts:

Rice, corn, sugarcane, grasses, and sedges.

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:

Infestation retards growth, decreases height, delays tillering, and reduces weight of dry matter.

Causes necrosis of penetrated epidermal cells, damage and destruction of cortical cells resulting in cavities in cortex, necrotic regions, and secondary invasion. 

This nematode occurs with H. spinicaudata in West Africa and the combination reduces rice yields by 20%.  In contrast to H. oryzae. H. spinicaudata survives well in dry soils.   

Previously, H. oryzae was thought to cause a serious disease of rice called "Mentek."

 

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Management:

Host Plant Resistance 

There is no significant resistance in rice varieties to H. oryzae, although there is considerable tolerance due to repeated individual selection.

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

For plants reported to have some level of resistance to this species, click

Soil Fumigation  

Fumigant nematicides are effective in dry fields, but economically questionable.

In trials conducted by A.L. Taylor in Thailand, treatment of soil in rice seedbeds with nematicides (1,3-Dichloropropene (Telone) (then D-D mixture), DBCP, or methyl bromide) and treatment of paddy soil with either D-D or DBCP (both by injection and then flooding) or by flooding and then mixing in DBCP or D-D, increased rough rice yields by 24 to 37%.  The weight of plants increased by as much as 95% and tillering increased as much as 43%.

Crop Rotation  

Rotation to non-hosts for 1 year is effective, but may be impractical.

Cultural Methods

A prolonged dry period between crops is effective, but may also be difficult to achieve.

Heavy fertilization has been recommended to help offset reduced yields.

In West Africa, H. spinicaudata can reduce rice yields by 20%, and can survive the dry season well in root debris; however, if the fields are flooded between crops, causing the roots to decay, hydrogen sulfide is released and H. spinicaudata survives poorly (research by Fortuner in Senegal).  But flooding may be difficult to achieve as river flow diminishes during the dry season, making water less available.

 

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References:

 

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Copyright © 1999 by Howard Ferris.
Revised: October 07, 2024.