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Dagger Nematode

Scientific Name
Xiphinema americanum
Scientific Author
(Cobb, 1913) Micoletzky, 1922
(Nematoda: Dorylaimida: Longidoridae)
Pest Status
0 Unknown
0 Unknown
NZ - Exotic
NZ - Exotic

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Diagnostic Images

Pharyngeal Region - Female
Slide mounted
Zeng Zhao Landcare Research
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Diagnostic Images (7)
Diagnostic Notes
Diagnostic characters: (Dr Zeng Qi Zhao, Landcare Research, Auckland, New Zealand).

These nematodes are minute (the largest species of the group being 2.2 mm in length), soft-bodied, vermiform, nearly transparent animals. They have a hard, needle-like 'stylet' (odontostyle and odontophore) at the mouth-end of the body which is capable of being extruded to puncture plant cells. The member species of the X. americanum group can be readily distinguished from other Xiphinema spp. by the following characteristics: small body length, relatively short (usually <150 ┬Ám) stylet (odontostyle + odontophore), thick cuticular lining of the Xiphinema americanum sensu lato pharynx, males usually absent, female genital branches equally developed, uterus short and without Z-organ, presence of symbiotic bacteria in the oocytes and in the intestines of juveniles, short conoid tail with rounded terminus, females without sperm, males with posteriormost medioventral supplement close to the paired precloacal papillae.

The separation of the individual species within the group is difficult and still subject to controversy among specialists. Lamberti & Bleve-Zacheo (1979) provide details of many of the species, and Ebsary et al. (1989) provide a key to the species occurring in North America.

Plants whose roots are being attacked by X. americanum sensu lato, in the absence of virus, generally show no clear characteristic symptoms in the aerial parts. With high populations, a general reduction in vigour is observed and this appears in characteristic patches in the crop corresponding to the highest concentration of nematodes. Under heavy attack, the roots show swellings close to the root tips. When nematode feeding results in virus transmission, the characteristic symptoms of the particular virus in the crop concerned develop. These usually first appear in the aerial parts of the plant in the growing season after transmission to the roots has occurred.

More Information
Specimen Contact
MAF Plant Health & Environment Laboratory (Nematode collection held by Zeng Zhao at Landcare Research)
Zhao, Z. Q. & Crosby, T. K.
26/05/2011 07:58 AEST
Last Updated
07/07/2011 07:55 AEST
Zhao, Z. Q. & Crosby, T. K. (2011) Dagger Nematode (Xiphinema americanum) Updated on 7/7/2011 7:55:04 AM Available online: PaDIL -
Image Use
Free for use under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)