Hemicycliophora arenaria

Taxonomy, Common Name, Disease

Hosts

Narrow host range. Citrus, tomato, beans, celery, squash, pepper, and Tokay grape; also Hymenoclea salsola (cheesebush) and coyote melon (Cucurbita palmata) on virgin desert soil.

Distribution

First reported from the Coachella Valley of California.

Life Cycle

Migratory ectoparasites feeding near root tip. The first occurs within the egg. Second and third stages must feed to develop. Sexual differentiation occurs after the third molt. Fourth stage and adult are persistent stages for females. Esophagus is degenerate in male juveniles, 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 approximately1 egg per hour in water. Egg hatch occurs in 3 to 5 days.

During feeding, the stylet is inserted 2-3 cells deep - through and between cells. Dorsal esophageal gland secretions directed into cell during 1-2 hour quiescent period; then cell contents are withdrawn over period of 2-6 days - regular pumping of median bulb. Nematode has a feeding tube (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.

Symptoms-Pathogenicity

Usually causes root-tip swelling and stunted root/plant growth. Root galls are formed by increase in cell divisions (hyperplasia), giving rise to enlarged cortex. Greenhouse tests - 36% growth reduction in citrus and 28% in tomato.

Management

Preplant nematicides. Postplant nematicides on perennials. Hot water treatment of bare-root trees (10 min. at 46 C.). Nematode is sensitive to reduced aeration, and mortality is associated with irrigation. Resistant crops include "Thompson Seedless" grape, cotton, and corn. Resistant rootstocks include trifoliate orange, sweet orange, sour orange, and Marsh grapefruit.

Characteristics

Hemicycliophora - Sexually dimorphic. Female 0.6-2mm long, rather stout, anterior end usually bluntly rounded, posterior end tapered to cylindrical with a bluntly rounded or cone-shaped terminus. Cuticle with two detached layers each layer with coarse, rounded annules. Esophageal region criconematid but the strong stylet, with rounded to backwardly sloping knobs, not anchor-shaped. Vulva posterior, V = 80-90%, anus and rectum indistinct. Males much thinner than females, esophagus degenerate, stylet absent; spicules strong, semicircular to hook-shaped, bursa adanal, well developed, tail long, narrowly conical. Juveniles similar to females, lacking the extra cuticular scales of juveniles in Criconemella.

References

  1. Evans, K., D.L. Trudgill, and J.M. Webster. 1993. Chapter 1. Extraction, Identification and Control of Plant Parasitic Nematodes. in Plant Parasitic Nematodes in Temperate Agriculture. CAB International, UK. 648 pages.
  2. Franklin, M.T. and A.R. Stone. 1974. Hemicycliophora arenaria. C.I.H. Descriptions of Plant-parasitic Nematodes. Set 3, No. 43. Commonwealth Institute of Parasitology. C.A.B. International. 3 pages.
  3. Jenkins, W.R. and D.P. Taylor. 1967. Chapter 15. Sheath Nematodes: Hemicycliophora and the Related Hemicriconemoides. in Plant Nematology. Reinhold Publishing Corporation, New York. 270 pages. (page 158).