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Nacobbus (Thorne and Allen, 1944)
Genus named for N.A. Cobb
The genus Nacobbus has only two species N. dorsalis and N. aberrans. 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).
|Pronounced sexual dimorphism.
Female: Adult female soft-bodied, swollen, spindle-shaped to globose.
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.|
Nacobbus aberrans and N. dorsalis, the two current species
of the genus, occur in the Americas.
Limited information is available on the less wellknown species N. dorsalis , which is present only in California where it has negligible economic importance
and 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).
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).
For an extensive list of host plant species and their susceptibility to this genus, copy the genus name
select Nemabase Genus Search and paste the name in the Genus box
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.
Galls on potato roots caused by Nacobbus aberrans. Photo by J.N. Sasser.
Luc, Rev. Nematol. 10(2):203-218 (1987)
Manzanilla-López, 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
Thorne & Allen, 1944 (Nematoda:Pratylenchidae):Systematics, distribution, biology and management. Nematropica 32:149-227.
Sher, S.A. 1970. Journal of Nematology 2:228-235.