Nacobbus dorsalis




Rev 09/13/2023

False Root-knot Nematode Classification Hosts
Morphology and Anatomy Life Cycle
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    Nacobbus dorsalis Thorne & Allen, 1944

    False Root-knot Nematode


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Morphology and Anatomy:

  Immature Females:
  • vermiform.
  • tylenchid stylet with well developed basal knobs;
  • head not off-set;
  • esophageal gland overlapping the intestine dorsally;
  • lateral field with four incisures;
  • monovarial
  • vulva close to the anus, sub-terminal
Mature Females:

Saccate (0.8 to 1.4 mm long and 0.2 to 0.45 mm wide).

Nacobbus dorsalis differs from N. aberrans in the number of annules between vulva and anus (VA = 8-14 in N. dorsalis compared to VA = 15-24 in N. aberrans) and a more posterior vulval position in the immature females (94-97% compared to 91-94 %, respectively). Mature N. dorsalis females are rounder compared to the spindle-shaped N. aberrans females.

Posterior of female - vulva and anus (SEM):

 Photograph: I. Cid. del Prado

Drawing by Charles S. Papp, CDFA


Vermiform and of the same body length as females.

Caudal alae peloderan.

Spicules and gubernaculum.

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

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In California, this species of false root knot nematode is found occasionally in Kern, King, Los Angeles, Monterey, Riverside, and San Luis Obispo counties.  Mainly on plants not of agricultural importance.

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Economic Importance:

D-rated pest in California Nematode Pest Rating System.

Mainly reported from non-agricultural plants, and quite rare.


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All juveniles are migratory endoparasites and penetrate plant root tips and/or axial roots.  

Mature females penetrate roots, become swollen and sedentary, cause formation of root galls and enlarged cells.

Nacobbus copy.jpg (41199 bytes)


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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

Eggs are retained in the female body in N. dorsalis.

Life cycle is approximately 48 days at 25 C.

The nematode migrates through plant tissues as a juvenile; it initiates a gall and becomes sedentary as a young female.

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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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Manzanilla-Lopez, R. H., M. A. Costilla, M. Doucet, J. Franco, R. N. Inserra, P. S. Lehman, I. Cid del Prado-Vera, R. M. Souza, and K. Evans. 2002. The genus Nacobbus Thorne & Allen, 1944 (Nematoda:Pratylenchidae):Systematics, distribution, biology and management. Nematropica 32:149-227.

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Copyright © 1999 by Howard Ferris.
Revised: September 13, 2023 .