Heterodera schachtii

Taxonomy, Common Name, Disease

Hosts

Narrow host range (sugar beet, cabbage, cauliflower, brussels sprouts, mustard, radish, spinach, chard).

Distribution

Widely distributed in all sugar beet growing areas of the world.

Life Cycle

Sedentary endoparasite. Second-stage juveniles that hatch from eggs are the infective stage. J2 enter behind the root tips where they feed on cells in the cortex and stele and giant cells are formed. As size increases during development (3rd and 4th juveniles stages) the swollen body bursts from the root tissues so that the adult females have the swollen portion of the body exposed on the root surface with the head and neck imbedded in the root. Adult females, which are white or light yellow in color, retain most of the eggs within their bodies and some are laid into a gelatinous matrix. Eggs laid in the gelatinous matrix hatch and the second-stage juveniles invade new roots. When the female nematodes are fully mature, or when feeding is interrupted, the body wall undergoes a tanning process and becomes brown in color. At this stage the dead female body containing eggs (about 300-500) is referred to as a "cyst". Eggs in the "cyst" may remain viable for long periods of time and may not hatch readily unless stimulated by root secretions, usually of host plants. Eggs within cysts remain viable for many years. Males are required for reproduction. The optimum temperature for growth and reproduction is 21-27C and development takes about 17 days.

Symptoms-Pathogenicity

Sugar beets are stunted, have yellow foliage and the plants wilt in warm weather. Sometimes the wilting persists in the presence of high moisture levels in the soil. Yields are severely reduced, the reduction in yield is correlated with the intensity of the infection. The white females and brown cysts attached to the roots are visible to the unaided eye.

Management

Crop rotation is made possible because of the restricted host range. Generally 3 to 4 years growing of non-hosts reduces soil populations to a low enough level to allow the growing of a susceptible crop for one year.

Characteristics

Heterodera - Sexually dimorphic, mature female obese, lemon-shaped, 0.5 - 1 mm long, with a distinct neck; vulva subterminal near anus and located on a terminal cone. Cuticle thick, whitish at first but gradually turns brown to black to form a cyst protecting the many eggs retained inside: two translucent areas, fenestrae, on either side of the vulval slit. In young females the excretory pore at the level of, or posterior to, the median esophageal bulb; stylet 20-30 um long with distinct basal knobs. Males elongate, about 1 mm vermiform, posterior region twisted through 90-180 degrees when killed by heat; tail bluntly rounded, very short without a bursa, spicules protruding subterminally, spicules slender 30-40 um long, curved ventrally; lip region offset with 3-6 annules, head skeleton well developed; stylet robust 20-40 um long with distinct basal knobs. Infective juveniles (J2) 0.4-0.6 mm long, almost straight when killed by heat. Lip region moderately sclerotized, stylet robust 20-30 um long with distinct basal knobs; esophagus with prominent median bulb and elongated basal lobe overlapping intestine mainly ventrally; tail conical, 3-4 anal body widths long, with a narrow rounded or pointed terminus; posterior part of tail (30-60%) a clear hyaline region.

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. 1972. Heterodera schachtii. C.I.H. Descriptions of Plant-parasitic Nematodes. Set 1, No. 1. Commonwealth Institute of Parasitology. C.A.B. International. 4 pages.
  3. Maggenti, A.R. 1981. General Nematology. Springer-Verlag, New York. 372 pages.
  4. McKenry, M.V. and P.A. Roberts. 1985. Phytonematology Study Guide. University of California Division of Agriculture and Natural Resources Publication 4045. 56 pages.
  5. Nickle, W.R. 1984. Plant and Insect Nematodes. Marcel Dekker, Inc. New York. 925 pages. Radewald, J.D. 1978. Nematode diseases of Food and Fiber Crops of the Southwestern United States. University of California, Division of Agricultural Sciences Priced Publication 4083. 64 pages.