Heterodera carotae

 

Contents

 

Rev 12/27/2013

Carrot Cyst Nematode Classification Hosts
Morphology and Anatomy Life Cycle
Return to Heterodera Menu Economic Importance Damage
Distribution Management
Return to Heteroderidae Menu Feeding    
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Classification:

      Tylenchida
       Tylenchina
        Tylenchoidea
         Heteroderidae
          Heteroderinae
Heterodera carotae (Jones, 1950)

Synonyms: None.

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Morphology and Anatomy:

Length = 218-625 (av. = 408) m; width = 165-500 (av. = 309) m.

Female: Adult white, lemon-shaped with large egg-sac often almost totally enveloping the female.

Head small, consisting of labial plate and a single annule.

Median esophageal bulb rounded with distinct valve.

Excretory pore behind the level of the median bulb, 81-119 m from the anterior extremity.

Paired ovaries almost fill entire body cavity.

Vulval slit in a cleft on cone-top.

Cuticular pattern at mid-body reticulate.

Cyst: Mature cysts small, lemon-shaped with distinct neck and vulval cone; neck often twisted. Color changes from white to russet-brown with no intermediate yellow stage. Wall-pattern consists of irregular zig-zag lines forming a close network. Subcrystalline layer present, but fragile.

Prominent vulval cone with gently sloping sides which blend smoothly into the body contour. Bullae absent. Underbridge about 90 m long, bifurcate, slender, unsclerotized and often lost during slide preparation. Vulval slit, 43-51 (av. 47) m long, occurs in a recessed cleft on the top of the cone and often appears partly open. Vulval lips unsclerotized. Fenestration indistinct, ambifenestrate. Vulval bridge frequently broken in older specimens.

Egg-sac large and usually filled with eggs, the sac often being as large as the cyst.

Male: Vermiform with short, bluntly rounded tail.

Head offset, 7 m long by 11 m at widest point, with 6-8 indistinct post-labial annules. Cephalic framework robust. Anterior and posterior cephalids at level of second and sixth body annules, respectively.

Spear strong with rounded basal knobs.

Dorsal esophageal gland orifice 5-7 m behind spear knobs.

Median esophageal bulb oval with poorly developed valve plates which are 85-105 (90 m) from anterior end.

Excretory pore 148-161 (av. 163) m from head. Hemizonid conspicuous, 2-3 annules long, located 6-9 annules in front of the excretory pore. Hemizonion inconspicuous.

Single testis uniformly packed with sperm and averaging 59% of total body length.

Spicules arcuate with a bulbous anterior part and tubular mid-part tapering into a twisted posterior section. Spicule tip bidentate. Gubernaculum slightly curved.

Phasmids ad-anal.

Lateral field with four lines forming three bands; outer lines crenate, outer bands areolated.

Second-stage juvenile: Head slightly offset with four indistinct post-labial annules. Cephalic framework less heavily sclerotized than the well- developed spear. Spear knobs have concave anterior faces. Cephalids indistinct; anterior ones level with third body annule and posterior part level with eighth-ninth body annule.

Dorsal esophageal gland orifice 5-6 m behind spear knobs.

Median bulb oval, but poorly developed. Median valve plates 61-72 m from anterior extremity.

Lateral field with four incisures forming three bands; outer lines crenate, outer bands areolated. Phasmids obscure, 3-4 annules anterior to excretory pore. Hemizonion obscure.

Genital primordium apparently consisting of two cells and located 60% of body length from head. Vast majority of juveniles exhibit typical Heterodera tail shape, but a small number per cyst show variations. The most common variation is the presence of 1-3 spherical refractive bodies within the tail, sometimes with associated swelling. In a few cases, the tail may be shortened to resemble that of a Meloidogyne juvenile.

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Distribution:

 

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Economic Importance:

 

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Feeding:

Feeding site establishment and development typical of genus.    

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Hosts:

 

For an extensive list of host plant species and their susceptibility, copy the name

Heterodera carotae

select Nemabase and paste the name in the Genus and species box

  
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Life Cycle:

The egg-sac juveniles hatch within a few days, even in the absence of a host plant, and may begin a second generation by invading young rootlets. Infective juveniles in cysts do not emerge until 2-3 months after the brown stage has been reached. Dehydrated egg-sacs may, however, persist in the soil either free or adhering to the cyst or to pieces of root.

Root invasion takes place in 36 hrs. at 18-20 C. Development of egg-sac starts about 4 weeks later. Some females even at maturity remain embedded within the root. Egg-sac rapidly fills with extruded eggs which are at first unembryonated, but later contain fully developed juveniles.

Adult males may be found after about 30 days; they are numerous and, in Italy, they were found free in the soil between October and November (Ambrogioni, 1970, 1971).

On carrots sown in March and harvested in July (England), only one generation developed, but on the main crop sown in May and harvested in November, it was possible for two generations to develop (Jones, 1950a). Two generations may also develop on greenhouse-grown carrots (Stelter, 1969).

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 5, No. 61 (1975)]

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Damage:

Patchy growth, yellowish leaves; distortion of tap root, due to early lignification, renders affected carrots unmarketable.

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Management:

Lamberti, et al. (1974) observed that two applications of 1,3-Dichloropropene (Telone), made at 3 and 4 weeks prior to sowing, result in highest increase in carrot yield.

Greco, et al. (1974) found that phenamiphos (500 kg/ha) or dazomet (500 kg/ha) gave high yield increases with respect to control. Acceptable results were also obtained with Di-Trapex (300 l/ha) and 1,3-Dichloropropene (Telone) (400 l/ha).

A range of other nematicides produce acceptable results, but are not economically feasible to use.

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

Heterodera carotae

select Nemabase Resistance Search and paste the name in the Genus and species box

 

[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 5, No. 61 (1975)]

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Copyright 1999 by Howard Ferris.
Revised: December 27, 2013.