Pests

Heterodera schachtii Schmidt - Sugar-beet Cyst Nematode

Systematic position.

Phylum Nematoda, class Secernentea, order Tylenchida, suborder Hoplolaimina, superfamily Hoplolaimoidea, family Heteroderidae, genus Heterodera.

Biological group.

Obligate parasite.

Morphology and biology.

Coelelminth of microscopic size. Female is lemon shaped, white (0.31-0.89 x 0.19-0.67 mm); male is vermiform, transparent (0.97-1.63 x 0.028-0.042 mm). Eggs are oval (0.122-0.14 x 0.049-0.053 mm); vermiform larvae of I and II instars (0.415-0.44 x 0.05-0.09 mm) develop there. The larvae of II instar move to wet soil down to 30 cm, searching for and invading roots of plant hosts (Cruciferae, Chenopodiaceae). In roots they become sedentary, feeding and developing into bottle-like larvae of III instar and lemon shape of IV instar; the latter larvae develop into females or males. Swollen bodies of larvae of IV instar break off the root cortex; mobile males penetrate into soil and the hind end of females becomes accessible for insemination. The majority of eggs (several hundred) are laid by females gradually. In the beginning, the eggs are deposited in yellow gelatinous matrix ("egg sack") where they develop the second generation. As a whole, there are 3 generations per season. At the end of plant vegetation period, the eggs with larvae remain in the body of dead female, whose external covers become hard and brown and turns into a cyst. The nematode cysts fall into soil. Within the cysts, the larvae keep in anabiosis 9 years in the absence of host plants (sugar beet, cabbage, rutabaga, rape, spinach, false flax, orach, common lambsquarters, wild cress, shepherd's purse). Cysts of H. schachtii spread with soil, water and wind.

Distribution.

The Sugar-beet Cyst Nematode is spread throughout Europe from Spain to Finland and Eire to Bulgaria. It is recorded in Turkey, Israel; in U.S. in both eastern and western states; in Canada, Australia, and South Africa. This species is distributed in all areas of sugar beet growing in fields and homestead lands. In 1960s the infestation of large areas in Central Chernozem zone and in the Caucasus was marked because of intensive growing of the culture. The same situation was also met in Kyrgyzstan and Kazakhstan in 1980s, being currently reported in Ukraine. In Western Siberia, H. schachtii is found in several agricultural farms. Mass distribution of Sugar-Beet Cyst Nematode is not recorded until recently in Northwest Russia, Byelorussia, and Baltic States.

Ecology.

This species is ecologically flexible, being distributed in all climatic zones. The main condition for accumulation of the species population is the frequency of growing affected cultures; the main condition for the nematode survival is field infestation. Abiotic conditions influence H. schachtii through the plant host. The optimal hydrothermal coefficient is 1-1.5. This species prefers light soils.

Economic significance.

The harmfulness of H.schachtii for sugar beet consists in the reduction of root yield. Thresholds of harmfulness depend on the main criterion; i.e., the infestation of soil before sowing (the number of larvae in 100 cm3 of soil). They vary by regions; e.g., 200 larvae are 5% threshold in Ukraine, but 10% threshold in Kyrgyzstan; under the infestation level 1300 larvae per 100 cubic cm, the yield losses amount to 40% and 50% correspondingly. Control measures include the use of unaffected crops and resistant varieties of sugar beet (e.g., Manon, Crocodile).

Reference citations:

Babich A.G. 1990. Harmfulness of sugar-beet cyst nematode and ways of its reduction in right-bank forest-steppe of Ukraine. PhD Thesis. Kiev: Ukranian Agricultural Academy. 17 p. (in Russian).
Chakayeva A.Sh. 1984. Sugar-beet cyst nematode in Kirghizia and the rationale of its control measures. PhD Thesis. Alma-Ata: Institute of Zoology of Ac.Sci.of Kazakh.SSR. 22 p. (in Russian).
Gus'kova L.A., Chakaeva A.Sh., Krasnozhenov P.I. 1981. Methodical recommendations on the detection of sugar-beet cyst nematode and its control. Frunze: Ministry of Agriculture of Kirghiz.SSR. 11 p. (in Russian).
Linnik L.I., Kitsno L.V., Babich A.G., Gus'kova L.A. 1989. Detection of sugar-beet cyst nematode and measures of its control (recommendations). Moscow: VO Agropromizdat. 17 p. (in Russian).
Polyakov I.Ya., Terent'yeva T.G., Gus'kova L.A., Antonova V.V. 1979. Distribution of nematodes - parasites of agricultural crops in the USSR. Moscow: VASKhNIL. 32 p. (in Russian).
Shesteperov A.A. 2007. Does soil exhaustion threaten sugar beet crops in Russia? Zashchita i karantin rastenii 7: 50-53 (in Russian).
Skarbilovich T.S. 1960. Sugar-beet cyst nematode and its control. In: Ershov V.S., ed. Transactions of VIGIS. V.8. Moscow: Ministry of Agriculture of the USSR - VASKhNIL. 274 p. (in Russian).

© Gus'kova L.A.

Picture © Gus'kova L.A.
 

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