Cyst nematodes (Globodera and Heterodera) are highly specialized in one or a few crops. These nematodes are found on all soil types and can survive for long periods. Damage is caused by deterioration of the root system and disruption of the hormone balance of the plant. The most prevalent species in the Netherlands are the potato cyst nematodes, Globodera pallida, Globodera rostochiensis, and the beet cyst nematodes, Heterodera schachtii and Heterodera betae.
The eggs of cyst nematodes hatch when attractants are secreted by a host plant. There is a natural decline in this secretion, so the infestation slowly decreases each year, but this rate of decline varies among nematode species. Once a juvenile has invaded the roots of a host plant, the plant responds by forming feeder cells. At this point, the juvenile is no longer mobile and molts.
The amount of food available determines whether the juvenile becomes male or female. If there is enough food, it becomes female; if there is a lack of food, on the other hand, it becomes male. The males are mobile and leave the roots, whereas the females stay in the root and swell until their abdomens burst out of the root. It is these swollen females that are the cysts which can be seen on the roots with the naked eye. The males fertilize the females, after which the eggs are deposited in the body of the female. When the female dies, her skin decays into a solid wall of cysts. These cysts can contain up to 600 eggs and provide good protection, allowing the eggs to survive in the soil for a long time.
There are several species of cyst nematodes in the Netherlands:
- Globodera pallida and Globodera rostochiensis (Potato cyst nematode)
- Heterodera schachtii (White beet cyst nematode)
- Heterodera betae (Yellow beet cyst nematode)
- Heterodera groettingiana (Pea cyst nematode)
- Heterodera carotae (Pea cyst nematode)
- Heterodera crucifera (cabbage cyst nematode)
- Heterodera trifolii (Clover cyst nematode)
- Heterodera mani (Rye grass cyst nematode)
- Heterodera avenae (Oat cyst nematode)
- Heterodera bifenestra (Oval grass cyst nematode)