One of the most diverse animal species on the earth, nematodes are roundworms that can thrive in different environmental conditions. Even though it is difficult to distinguish individual nematode species, around 40,000 species have been identified so for. But, estimates show that there are more than 1,00,000 species of roundworms or nematodes on the Earth.
Among the 40,000 species that have been recognized, some are parasitic in nature. A few among them attack plants and feed or live on plant tissues. Most of the others live in soil, feeding on the organic matter, insects, larvae, and bacteria. It is the insect parasitic nematode species that are useful in organic pest control.
Harmful and Beneficial Nematodes
While nematodes like hookworms, pinworms, and whipworms are parasitic on humans, Dirofilaria immitis can cause heartworms in dogs. Similarly, there are various plant parasitic nematodes, like potato cyst nematodes (Ditylenchus and Globodera) and soybean cyst nematodes (Heterodera).
However, there are some beneficial nematodes that can be used in agriculture/horticulture. These nematodes are parasitic on garden pests, like infects, larvae, and bacteria. These nematodes are among the most efficient agents for biological pest control.
Such insect parasitic nematodes are mostly found in the families Steinernematidae and Heterorhabditidae. Among the different nematode species in these families, the most commonly used are Heterorhabditis heliothidis, Steinernema carpocapsae, Steinernema glaseri and Heterorhabditis bacteriophora.
Beneficial nematodes are effective in controlling a wide range of pests, like grub worms, fleas, mole crickets, scarab and Japanese beetles, cucumber beetles, billbugs, pine beetles, cabbage worms, thrips, ants, termites, and weevils. Steinernema carpocapsae is found to be the most effective nematode for flea control.
Benefits of Nematodes
As mentioned earlier nematodes that are parasitic on insects are used in organic gardening, as a means of biological pest control. These nematodes have a life cycle of six stages - eggs, four stages as larvae and adults. It is during their third stage as larvae, that they enter the body of hosts.
In most cases, insect larvae are the most probable hosts of these beneficial nematodes. They enter the body of the host through the anal opening, mouth, breathing holes, or through holes made on the body wall. Once they gain entry, the nematodes release Xenorhabdus bacteria (present in their intestines and pharynx) into the body of the host.
The bacteria break down the internal organs of the host with the help of enzymes. Thus the body of the host becomes food for the nematodes. Once the bacteria are released into the host, it takes only 24 to 48 hours, for the host to get killed. The nematodes grow to become adults that produce young ones, before exiting the remains of the host.
If you are planning to use beneficial nematodes, you must get the right type from a reputed supplier. It will be better to consult an expert, for choosing the right nematode for the specific pest. Make sure to adhere to the instructions given by the manufacturer, for storing and applying these nematodes.
It will be better to retain the moisture of the soil, while applying these nematodes. Even the number of nematodes to be applied must be determined on the basis of the area to be covered.
While you require one million nematodes for an area of 2000 square feet, it will take around 24 million to cover an acre of land. All you have to do is to mix them in water, before spraying on the soil. In short, beneficial nematodes are always preferred, as they are effective.