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Tylenchida Tylenchina Tylenchoidea Heteroderidae Heteroderinae
Heterodera avenae Wollenweber, 1924
Cereal cyst Nematode
|Female: Length = 0.55-0.77 mm;
width = 0.36-0.5. mm. Adult lemon-shaped, with prominent
neck and vulval cone.
Lip region annulated, with 6 confluent lips and a labial disc.
Spear straight to slightly arcuate, 26-32 µm long; basal knobs rounded.
Median esophageal bulb rounded, with a distinct valve.
Vulva is a 12-13 µm long slit; may have gelatinous extrusion, but eggs rarely, if ever, extruded. Zigzag, rugose cuticular surface pattern. Subcrystalline layer consipcuous, sloughing off as the dark brown cyst is formed. This layer now known to consist of cosanoic acids and their calcium salts (Brown et al., 1971).
Vulval cones of cysts mainly occupied by hyaline vaginal structure. Bullae prominent, crowded beneath vulval cone. Ambifenestrate.
Most cysts contain 200-250 eggs, but large ones may contain more than 600 (Anderson, 1961). Average cyst size 0.71 mm x 0.50 mm (Triffit, 1929).
No yellow phase as the maturing cyst changes from white to dark brown (Franklin, 1951). Mean of 20 eggs from neotype locality (Aschersleben, Germany): 126 µm long, 56 µm wide.
Male: Length 1.07-1.59 mm. Abundant, vermiform, length averaging 1.38 mm for 100 individuals (Franklin, 1951) but often much shorter--particularly those developing in H. avenae-resistant cereals.
Lip region rounded, offset, with 4 to 6 (usually 5) annules; framework heavily sclerotized with conspicuously marked outer margins. Cephalids indistinct, anterior 1 to 2 and posterior 6 to 7 annules behind lip region.
Anterior tapering part of spear sharply pointed, usually a little shorter than half the spear length; basal knobs of spear rounded, usually with flat, posteriorly sloping anterior surfaces.
Orifice of dorsal esophageal gland 3 to 6 µm behind spear base.
Median esophageal bulb oval with distinct valve.
Esophageal glands ventral and ventro-lateral to intestine; dorsal with larger nucleus located closely behind esophago-intestinal junction, subventrals extending past the dorsal.
Excretory pore near esophago-intestinal junction. Hemizonid distinct, 2 to 3 annules long, usually 5 to 6 annules anterior to excretory pore, but occasionally only one or 2 annules anterior. Hemizonion indistinct, 6 to 7 annules behind excretory pore.
Spicules arcuate, with medium-sized ventral flanges and notched end; together forming a narrow tube distally.
Gubernaculum simple, slightly curved.
Tail end usually twisted.
Vermiform, with a sharply pointed tail.
Lip region rounded, offset, with 2-4 annules.
Spear well developed, with large, anteriorly flattened to concave basal knobs; its anterior tapering portion less than half its length.
Median esophageal bulb rounded, very muscular, with a large valve.
Esophageal glands as described for the male, not filling the body cavity.
Tail 3-4.5 times anal body width long; body contents extend 1 to 1.5 body width into tail cavity. Hyaline portion 35-45 µm or about one-and-a-half spear lengths long. Lateral fields disappearing near middle to tail.
Phasmids pore-like, distinct, just behind anal level. First- and second-stage juveniles folded 4 times within the egg.
[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 1, No. 2 (1972)]
Canada, Europe, Australia, India, Japan, and U.S. [in California and Oregon (Oregon since 1972); nematode damages wheat in Idaho.
A-rated pests in California.
Feeding site establishment and development typical of genus.
Disruption of vascular tissues by syncytium incited by Heterodera avenae
Oats, wheat, barley, rye, occasionally maize; many grasses as alternate hosts.
For an extensive list of host plant species and their susceptibility, copy the name
select Nemabase and paste the name in the Genus and species box
About 6 pathotypes of H. avenae occur in Europe; there may also be pathotypes in Australia; may be up to 20 biotypes worldwide.
This species is not known to complete more than 1 generation per year.
A chill factor may be involved in hatching; rate of hatch can be increased by cereal root exudates.
Mobile, second-stage juveniles leave the cysts in Feb. to April in Northern Hemisphere and May to June in Southern Hemisphere (Banyer & Fisher, 1971a) and enter the host roots just behind the growing point. They come to lie parallel to the main axis with their heads just within the endodermis.
Syncytia develop in response to the J2 (Johnson & Fushtey, 1967), which develops through a series of 3 more molts to release the mobile male about 3 weeks after invasion; the sedentary, egg-bearing female matures from 6 to 9 weeks after invasion.
While European populations of H. avenae do not survive desiccation well, Australian and Indian populations are better adapted to more arid conditions.
H. avenae hatches best at around 10 C (50 F), though the temperature requirements can be complex.
[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 1, No. 2 (1972) and H. Ferris.]
Causes yellowing of plants; much branching and some swelling of roots may occur, particularly in oats and wheat. Seminal roots are usually most affected.
The worst damage to crops follows moist, cool periods at the time of larval hatch and invasion, and a dry period during the most active growing phase of the host crop (Fidler & Bevan, 1963; Dixon, 1963).
In autumn-sown wheat in Australia, damage is most severe following early start of the rainy season, attributed to increased juvenile emergence and mobility (Meagher, 1970).
Crop rotation is effective - this species declines more rapidly in the absence of a host than either G. rostochiensis or H. schachtii.
Nematicides are effective, but not economical unless used for more than one crop.
Resistant plant cultivars are being developed in several breeding programs, e.g. in Australia.
Host Plant Resistance, Non-hosts and Crop Rotation alternatives:
For a list of plant species or cultivars (if any) reported to be immune or to have some level of resistance to this nematode species, copy the name
select Nemabase Resistance Search and paste the name in the Genus and species box