Hemicycliophora arenaria

Hemicycliophora arenaria	Contents	Rev 10/16/2008
Sheath Nematode	Classification	Hosts
	Morphology and Anatomy	Life Cycle
Return to Hemicycliophora Menu	Economic Importance	Damage
	Distribution	Management
Return to Criconematidae Menu	Feeding	References

Classification:

      Tylenchida
       Tylenchina
        Criconematoidea
         Criconematidae
          Hemicycliophorinae
           Hemicycliophora arenaria Raski

Hemicycliophora arenaria was described by Raski (UC Davis), extensively researched by Van Gundy (UC Riverside).

Morphology and Anatomy:

Female and all juvenile stages have sheath; also sloping stylet knobs.

Males are rare, have degenerate esophagus and no stylet or sheath.

Distribution:

First reported from the Coachella Valley of California on rough lemon rootstock (Citrus jambhiri).

Feeding:

True ectoparasites.

Second and third juvenile stages must feed to develop.

Males have no stylet and do not feed.

Feeding Mechanism: stylet is inserted 2-3 cells deep - through and between cells. Dorsal esophageal gland secretions pass into food cell during 1-2 hour quiescent period; then cell contents are withdrawn over period of 2-6 days during which there is regular pumping of median bulb.

The nematode has a feeding tube similar to Trichodorus (adhesive
polysaccharide tube) which becomes firmly attached to root, and nematode has to writhe and twist to detach. Nematodes may appear as a fringe around root tip.

Nurse cells increase in volume, and walls thicken; some cells are multinucleate. Cells collapse when depleted and are pushed to the surface by meristem activity, thus providing a continuous supply of new food cells for the nematode.

Root-tip galls are formed by increase in cell divisions (hyperplasia), giving rise to enlarged cortex.

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Hosts:

Citrus, tomato, beans, celery, squash, pepper, and Tokay grape.

Also Hymenoclea salsola (cheesebush) and coyote melon (Cucurbita palmata) on virgin desert soil.

Non-host crops include "Thompson Seedless" grape, cotton, and corn.

Resistant rootstocks include trifoliate orange, sweet orange, sour orange, and Marsh grapefruit.

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Life Cycle:

Life cycle consists of 4 molts, the first occurring within the egg.
A period of feeding is necessary between each subsequent molt.
Sexual differentiation occurs after the third molt. Fourth stage and adult are persistent stages for females; adult males have no stylet, do not feed, and are not persistent.
Adult female produces a sixth cuticle, so that it is ensheathed with two cuticles throughout its entire life.
Life cycle from egg to egg requires 15 to 19 days at 28 to 30 C on tomato.
Females can lay approximately 1 egg per hour in water.
Egg hatch occurs in 3 to 5 days.
Esophagus is degenerate in male juveniles.

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Damage:

Greenhouse tests - 36% growth reduction in citrus and 28% in tomato.

Damage and symptoms of H. arenaria on rough lemon seedling (left); healthy seedling on right.

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Management:

Use trifoliate orange rootstocks in citrus.

Methyl bromide applied at rate of 200lb/acre eradicates nematodes to soil depth of 3 ft.

DBCP was used at rate of 2 to 4 gal/acre in 6 inches of water to kill 98.7 to 100% of the nematodes in the top 5 ft. of soil.

Hot water treatment of bare-root trees (10 min. at 46 C.) effective.

Hemicycliophora arenaria is sensitive to reduced aeration, and mortality periods are associated with irrigation. Fewer nematodes are observed in summer when more water is applied; higher summer temperatures may also reduce numbers, although nematode is able to flourish at 30 C.
Van Gundy and students observed that frequent irrigation (saturated soil conditions) kept populations at lower levels.

Note: In 1992, attempts to find H. arenaria in the Coachella grapefruit orchard in which Van Gundy worked have been unsuccessful. There have been annual applications of the nematicide Nemacur (phenamiphos) to the orchard.