Scutellonema brachyurum

Scutellonema brachyurum	Contents	Rev 05/05/2008
	Classification	Hosts
	Morphology and Anatomy	Life Cycle
Return to Scutellonema Menu	Economic Importance	Damage
	Distribution	Management
Return to Hoplolaimidae Menu	Feeding	References

Classification:

Tylenchida Tylenchina Tylenchoidea Hoplolaimidae
Hoplolaiminae

Scutellonema brachyurum (Steiner, 1938) Andrássy, 1958

    Synonyms:
      Rotylenchus brachyurus Steiner, 1938
      Rotylenchus coheni Goodey, 1952
      Scutellonema coheni (Goodey, 1952) Andrássy, 1958
      Scutellonema boocki Lordello, 1957

Morphology and Anatomy:

Length, female: 0.82 mm av.; length, male: 0.63-0.85 mm.

Female:

Body forming a single spiral (occasionally arcuate); annulations distinct, average annule width 1.4 µm near midbody.
Lateral fields about one fourth as wide as body, areolated from the anterior to the excretory pore and at phasmids, marked by 4 incisures.
Lip region hemispherical, slightly set off by a constriction, with 3 to 4 (sometimes 5) annules of irregular width and a terminal flat labial disc; basal annule marked by 6 longitudinal striae; framework strongly sclerotized, its outer margins inwardly concave, extending posteriorly one body annule.
Stylet well developed, 26-30 µm long, in two almost equal parts; basal knobs prominent, rounded with slightly flattened anterior surfaces, 4.5 µm across.
Dorsal esophageal gland opening rather obscure, about 5 µm behind spear knobs.
Cephalids, hemizonid, and hemizonion indistinct.
Esophagus typical of the genus, slightly contracted at base of isthmus.
Median esophageal bulb ovoid, extending over 8 body annules.
Nerve ring encircling isthmus a little behind median bulb, well anterior to excretory pore which lies at approximately 88 body annules behind the lip region and about one body-width behind the esophageal glands.
Esophageal glands overlap intestine dorsally.
Gonads amphidelphic, symmetrical, on left side of intestine. Ovaries outstretched with oocytes in a row except for 4 or 5 in multiplication zone near tip. Single egg in posterior uterus. No spermatheca or sperms in uterus. Epiptygma double, indistinct, not projecting out through vulva.
Intestine extending slightly over rectum.
Tail broadly rounded, about half anal body-width long, annulations following tail contour; annules slightly irregular and coarser than adjacent body annules; 8 annules between anus and tail tip.
Phasmids enlarged, 3-4 µm in diameter, just pre-anal. Term "scutellum" refers to Latin "shield" for shape and size of phasmids - hence Scutellonema.

Male: Rare, absent from most populations. Similar to female in most details.

Spicules arcuate, slightly cephalated, 25-27 µm long.

Gubernaculum large, protrusible.

Bursa crenate, terminal.

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 4, No. 54 (1974)]

Distribution:

Cosmopolitan; may be native to Africa where it is common in uncultivated soil.

Occurs on 85 plant species in California (Siddiqui et al.).

Feeding:

Ectoparasite of roots, but may invade the deeper cortical layers and become endoparasitic.

In african violets, the nematode was found both within and between cells; several eggs were seen within a single cell, where the juveniles may hatch and develop to fill the cell completely before migrating through the wall to the adjacent cells (Golden, 1956).

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Hosts:

Soybean, tobacco, sweet potato, alfalfa, barley, rice, tea, sugarcane, and ornamentals

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Life Cycle:

On suitable hosts, S. brachyurum quickly builds up to large populations.

Different initial populations when inoculated on red clover reached a very high ceiling level after 325 days, and there was no apparent injury to the host.

On hairy vetch, greatest population increases occured at 28 C, while at 18 C, reproduction was considerably retarded (Malek & Jenkins, 1964).

In the greenhouse, in 7 months, S. brachyurum increased 3.8-fold on tulip tree and 17-fold on sycamore (Ruehle, 1971).

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Damage:

Goodey (1952) observed that parasitized roots of Hippeastrum sp. showed reddish lesions which later turned brown. The internal root cavities produced by the nematodes became isolated by a new tissue - the wound periderm.

Graham (1955) demonstrated that S. brachyurum is pathogenic to, and produces lesions on the roots of, tobacco grown under greenhouse and field conditions. Affected plants of Golden Cure Tobacco showed reduced root weight, top weight, and reduced height compared to non-inoculated plants.

Luc (1959) found this nematode associated with poor growth of sugarcane in Malagasy.

There is no record of associations of this species with other pathogens.

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Management:

Grass rotations between tobacco crops in Zimbabwe can be effective (Shepherd, 1968).

Fumigation with DBCP eliminated Scutellonema populations in cotton grown in Tanzania.

Heat treatment and use of nematicides on amaryllis bulbs grown in the greenhouse have been employed (Johansson & Niedieck, 1964).