Beet cyst nematode
| Beet cyst nematode | ||||||||||||
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Beet cyst nematode ( Heterodera schachtii ) |
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| Scientific name | ||||||||||||
| Heterodera schachtii | ||||||||||||
| A. Schmidt , 1871 |
The beet cyst nematode ( Heterodera schachtii , also beet nematode, beet nematode) is a roundworm that parasitizes beet roots as an endoparasite . Heterodera schachtii was first described in 1859 by the Bonn botanist Hermann Schacht and systematically classified by Schmidt in 1871 and named after Schacht. The sugar beet is less likely to be attacked by Heterodera betae . The genus Heterodera also includes the soybean cyst nematode ( Heterodera glycines ), cereal cyst nematodes ( Heterodera avenae , Heterodera filipjevi , Heterodera latipons ) and numerous other species.
features
Heterodera schachtii is bisexual; the two sexes have different shapes ( sexual dimorphism ). While the males are worm-shaped, the females form a lemon-shaped shape and have a length of 0.8 mm.
development
The larvae develop in the egg in the body of the female. After hatching for the first time, they are still in a dormant state in the egg shell. The cuticle of the dead female hardens and turns into a cyst , in which the larvae that are resting in the egg shell are located. Under suitable conditions (soil moisture, soil temperature and soil aeration), root excretions from host plants activate the larvae. They actively hatch from the egg shell and cyst and migrate to the roots of the host plant. However, they can persist in the cyst for up to ten years.
With the help of a spike, the larvae then penetrate the plant tissue of the root. In the central cylinder of the root, they release saliva into a single cell through the mouth sting. The cell reacts with a local breakdown of the cell wall and thus fuses with the neighboring cells to form a syncytium , from which the larva takes all of its food for its development.
The larvae then develop into males and females through two further stages.
Harmful effect
The beet cyst nematodes cause beet fatigue . This occurs when beets and other host plants (all beet species of the Beta genus and the species of the goosefoot family , such as spinach), but also Brassica species such as rapeseed , are planted again and again on the same area. In the case of sugar beets , for example, it leads to increased formation of side roots ("beard") and reduced growth of the beet - and thus to a loss of yield.
Countermeasures
The population density can be kept low or reduced by a crop rotation in which sugar beet is only grown every 4 years or less. In addition, resistant catch crops such as resistant yellow mustard or resistant oil radish can be grown. These release attractants and thus induce the larvae of the nematodes to leave their cysts and migrate into the resistant plants. In contrast to the host plants, the nematodes in the resistant oil radish and yellow mustard varieties cannot form permanent, functional nutrient cells, i. H. the immigrated larvae starve to death or develop into males (females need 40 times more food to develop cysts than they develop into males). This principle of biological nematode control has been further developed since the late 1970s and some varieties of oil radish are now able to reduce the population of beet nematodes in cover crop cultivation by over 90% under favorable cultivation conditions. After that, sugar beets can be grown in the following growing year without damage.
In the meantime, nematode-resistant and nematode-tolerant sugar beet varieties are also on the market. While the nematode-resistant varieties largely prevent nematode development and reduce the population density in the soil with a slightly lower yield potential, the nematode-tolerant varieties tend to lead to a slight increase in population density, but show no yield losses even with higher population densities.
Neutral plants that neither release attractants nor are attacked are kidney beans , hemp , poppy seeds , chicory , rye , alfalfa , corn and phacelia .
No synthetic chemical agents ( nematicides ) for soil disinfection are permitted on the German market .
literature
- Spectrum of Science , September 2006, pp. 68ff.
Web links
- Heterodera schachtii in Fauna Europaea
- Bayr. State Institute for Agriculture
- Article in Hortipendium