Nematodes – A Hidden Threat
However, nematodes are difficult to see, as they hide in the soil where they attack the roots of the crops. Even when you dig up the roots they are often overlooked, as they are so small and translucent. You need a microscope to observe them. However, by the time the root damage is visible to the naked eye, it is often too late.
The damage by nematodes is estimated to cause a yearly loss of about 100 billion US$ in agricultural crops, despite all the currently used methods for nematode control! For cereals alone it is estimated that farmers could lose around 5% of their crop due to nematode infestation, that number can reach 20% when it comes to some of our staple vegetables such as potato and tomato.
There are about 20,000 different nematode species known, and approximately 4,000 of them feed on plant roots. These plant parasitic nematodes can be clustered into three groups: Root knot nematodes which form root galls (tumor-like) and, affect multiple crops; Cyst nematodes which as the name indicates form cysts (hard-shelled sacs containing eggs) on the root surface and are rather crop specific; and, migratory nematodes which can cause lesions to many crops.
Global Segment Manager FVI
The most damaging nematodes in agriculture are the root knot nematodes. When they move in large numbers into the roots to feed, the root system is no longer able to provide sufficient water, nutrients and energy to the parts of the plant above ground. The plants attacked by root nematodes show reduced growth, and as the root damage increases they wilt and finally die, resulting in total loss – worst case.
Today it is possible to follow the life cycle of the root knot nematode with the aid of an electron microscope. Its life starts with an egg less than 0.1 millimeter long. The 1st larval stage develops within this egg, and the worm shape can be seen though the egg shell. In the 2nd stage the larvae hatches out of the egg, it is mobile and attacks the roots tips. The nematodes settle in the root and cause the tissue to form giant cells. This provides more food and gives them protection. The female can be recognized by its sphere-like body shape, bloated by the eggs she carries inside. Females are considerable bigger, yet still of less than half a millimeter in diameter. The eggs are released from the body into the surrounding area. Each female can produce more than 1000 eggs or about 80 eggs per day! While the whole life cycle of root knot nematodes depends on the soil temperature, it usually takes approximately five weeks for the new eggs to hatch. Then the process starts all over again, with constantly increasing numbers of mobile larvae attacking the roots. A creepy picture if you see it close up with a microscope!
Nematodes – A Hidden Threat
So, what can be done to prevent nematodes from massively attacking plants and destroying crops? The best approach is to reduce the initial number of nematodes in the soil through good soil preparation, sterilization, etc. Another way to contain their population is through planting tolerant crop varieties or to change to another crop which is less sensitive to the specific nematodes. In intensive agricultural production additional use of effective nematicides are needed to achieve sufficient nematode control, which should be applied early to reduce the nematode pressure right from the beginning. Because they are so many and reproduce so quickly, full eradication of nematodes cannot be achieved. However, by keeping their numbers low the roots can stay healthy enough to do their job properly!
The knowledge about nematodes, their damage to the crops and possibilities to control the nematode populations is rather limited in many territories in the world. This is due to the fact that farmers often do not see them, but also sometimes it is the lack of experience and expertise about nematodes even within the agronomic community. At Bayer we do trainings in many countries to increase the awareness and knowledge about this threat and provide information about the available solutions. Stay tuned to learn more about how we can help plants thrive.