Rev 06/07/2021

Classification Hosts
Morphology and Anatomy Life Cycle

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          Nacobbus (Thorne and Allen, 1944)


Genus named for N.A. Cobb

The genus Nacobbus has three species N. dorsalis, N. aberrans and N. bolivianus. Of these, N. dorsalis is quite rare and reported mainly (maybe only) from isolated locations in California, but N. aberrans is an important pest of sugarbeet in North America (Mexico and western USA) and of potatoes in South America. Other described species, N. batatiformis and N. serendipiticus were synonymized with N. abberans by Sher (1970) although the type material available has been considered inadequate for that purpose (Stone and Burrow, 1985).  Later, N serendipiticus bolivianus was resurrected and elevated to N. bolivianus based on molecular differences among Central and South American populations previously considered to be N. aberrans (Reid et al., 2003).

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Morphology and Anatomy:

Pronounced sexual dimorphism.  

Female:  Adult female soft-bodied, swollen, spindle-shaped to globose. 

Deirids absent.  

Lip area rounded, not set-off (except in mature females).  Labial disc rounded, conspicuous; submedial sectors rounded, separated; lateral lip sectors reduced or absent.  

Esophageal glands in line with a long dorsal overlapping of the intestine. Esophago-intestinal valve undeveloped. 

Female genital tract with anterior branch very developed; posterior branch completely regressed with no trace of postuterine sac (i.e. single ovary).  

Vulva very posteriorly situated.  

Tail short, extremity rounded.  

Phasmids punctiform, in anterior half of tail.  

Drawing by Charles S. Papp, CDFA
Male: Small bursa enveloping tail.

Gubernaculum plain, not protruding from cloaca.

[Ref: Luc (1987), and H. Ferris.]

Body size range for the species of this genus in the database - Click:
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Nacobbus aberrans, N. dorsalis and N. bolivianus are the current species of the genus. They occur in the Americas. In 2003, Reid et al resurrected an earlier-described species, N serendipiticus bolivianus and elevated it to N. bolivianus based on molecular differences among Central and South American populations previously considered to be N. aberrans (Reid et al., 2003).
Limited information is available on the less well known species N. dorsalis which is present only in California where it has negligible economic importance; it parasitizes only a few non-cultivated plants without evidence of attack on agricultural crops. In contrast, N. aberrans is an important pest in temperate and subtropical latitudes of North and South America (Manzanilla-Lopez et al., 2002).

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Economic Importance:


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Juvenile stages are migratory endoparasites (characteristic of Pratylenchidae); females remain sedentary in galls. 

The parasitic habits include similarities to both root lesion and root-knot nematodes. The migratory and vermiform juveniles and immature adults behave like lesion nematodes, causing cavities and lesions inside the root tissues, whereas the mature females are sedentary and obese and induce root galls and specialized feeding sites (Manzanilla-Lopez et al. 2002).


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For an extensive host range list for this genus, click
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Life Cycle:

For Ecophysiological Parameters for this genus, click 

Eggs are deposited in a gelatinous matrix with a few retained in the female body in N. aberrans; they are mainly retained in the body, which becomes filled with eggs, in N. dorsalis.



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Galls on potato roots caused by Nacobbus aberrans.  Photo by J.N. Sasser.

Comparison of the galling symptoms caused by Nacobbus aberrans and Meloidogyne incognita on tomato.
Left: the "rosary bead" pattern typical of Nacobbus and the coalesced galling of a heavy Meloidogyne infection.
Photographs by Marco Antonio Magallanes Tapia, PhD Thesis, Colegio de Postgraduados, Texcoco, Mexico, 2021
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Various integrated schemes inolving crop rotation, organic amendments, biological antagonistts and biofumigation have proved effective in experimenatl trials for management of N. aberrans (Cid del Prado-Vera, 2005; Manzanilla-Lopez et al., 2002).


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Cid del Prado Vera, F. Franco J.C. Alejo, R. Flores C., J.A. Hernandez, R. Manzanilla L. and K. Evans. 2005.  Characteristics and Ecology of Nacobbus aberrans in Mexico.  California Nematology Workshop.

Luc, Rev. Nematol. 10(2):203-218 (1987)

H. Ferris.

Magallanes Tapia, M.A. 2021. Paquete Tecnologico para el Manejo de los Nematodos Nacobbus aberrans y Meloidogyne incognita en tomate de invernadero. PhD Thesis, Colegio de Postgraduados, Campus Monteciilo, Texcoco, Mexico.

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.

Reid, A., Manzanilla-Lopez, R. H., Hunt, D.J. 2003. Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae); a nascent species complex revealed by RFLP analysis and sequencing of the ITS-rDNA region. Nematology 5:441-451.

Sher, S.A.  1970.  Journal of Nematology 2:228-235.


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Copyright © 1999 by Howard Ferris.
Revised: June 07, 2021.