Pratylenchus penetrans - The Root-Lesion Nematode

Taxonomy, Common Name, Disease

Hosts

Wide host range. More than 350 hosts have been recorded. Apple, cherry, other fruit trees, conifers, roses, tomato, potato, corn, sugarbeets, and many other plants are parasitized by this nematode.

Distribution

Mainly found in temperate areas (USA, Europe, Australia, Canada, Egypt, India, Japan, New Zealand, Peru, Philippines, Rhodesia, Russia, South Africa, Tunisia).

Life Cycle

Migratory endoparasite. Reproduction is sexual. Females lay eggs singly in roots or in soil. Second-stage juveniles hatch from eggs, feed, and undergo three molts to the adult stage. The complete life cycle takes 30 to 86 days, depending on temperature, and is shortest at 30 C. Adults, J2, J3 and J4 can all invade roots. If conditions in the root become unfavorable any juveniles stage or the adult nematodes may leave the root and invade other nearby roots. Invasion usually takes place in the region of elongation.

Symptoms-Pathogenicity

Root-lesion nematodes feed upon cells in the root cortex. Cells are killed and in many instances small roots are killed. The migratory parasitism of this nematode opens up roots to secondary invasion by other soil microorganisms such as fungi and bacteria. In some hosts such as walnut, and stone fruits the nematodes may establish colonies in larger roots and large necrotic lesions are formed. Plants infested with root--lesion nematodes grow poorly, the foliage is frequently chlorotic and sparse and the terminal growth of branches may be suppressed. Crop yields are reduced. Seedlings planted in infested soil frequently fail to grow to normal size and may never produce satisfactory trees or vines.

Management

Preplant nematicides. Because of its wide host range, crop rotation is usually not feasible.

Importance

The most important nematode pest in the northeastern US.

Characteristics

Pratylenchus - Small nematodes, adults usually less than 1 mm long. Head region low and flattened, with 2, 3 or 4 head annules, with a distinct head skeleton and continuous with body contour. Stylet 20 um or less, moderately developed with distinct basal knobs. Esophagus with a well developed median bulb, the posterior gland lobes overlap the intestine ventrally. Female with posterior vulva (V = 70-80%) with a single anterior gonad and a short post vulval sac; tail cylindrical to conoid, two to three anal body widths long. Male tail conical with a distinct bursa that reaches the tail tip.

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. Corbett, D.C.M. 1973. Pratylenchus penetrans. C.I.H. Descriptions of Plant-parasitic Nematodes. Set 2, No. 25. Commonwealth Institute of Parasitology. C.A.B. International. 4 pages.
  3. Agrios, G.N. 1969. Plant Pathology. Academic Press, New York. 629 pages. (page 534).
  4. Nickle, W.R. 1984. Plant and Insect Nematodes. Marcel Dekker, Inc. New York. 925 pages. (pages 194, 333).
  5. Nickle, W.R. 1991. Manual of Agricultural Nematology. Marcel Dekker, Inc., New York. 1035 pages. (page 392).