Summary: Having trouble with wilting garden plants? The trouble might be parasitic nematodes feeding on the plant roots. Nematodes are also known as roundworms.
They look like worms, but they sit in a class of their own. They're nematodes; small, worm-like animals found in every environment on earth. Nematodes live in freshwater, marine water, and the soil. They can even be found in Antarctica and deep ocean trenches. They also often live in animals as parasites.
There are probably a half-million different species of nematode, but there are only about 80,000 that have been classified. Most nematodes are microscopic, but a few that live in large animals can grow over a meter long. (The nematode that ate Kansas City. Bet you don't remember that one!)They don't have bones and aren't very good at moving about, depending on water currents or disturbances in the soil to be transported from place to place. They can also be spread to humans by blood sucking insects or by eating uncooked meat. One of the reasons you don't see beef tartar on U.S. menus anymore.
Nematodes are either free living or they depend on a host and are parasitic. Free living nematodes often feed on algae, bacteria, or protozoa. Many parasitic nematodes are considered pests because they cause diseases in plants and animals, but others are considered beneficial because they attack pest species. You can have the pest nematodes and I'll keep the beneficial ones.
Nematodes that live in humans include whipworms, hookworms, pinworms, and Trichinelle spiralis, which are the cause of trichinosis. Now you know why your mother always told you to wear shoes outside. The root knot nematode, foliar nematode, and potato cyst nematode are a few nematode species that are parasites of plants. Beneficial nematodes are sometimes purposely added to the soil for biological control of cutworms, Japanese beetle grubs, and mole crickets, among others. Biological control using nematodes has been around for a while, but is still being developed to make the treatment more efficient.
Because nematodes are so small and so ubiquitous, there is no way to get rid of all nematodes living in the soil, even if you wanted to. You can try to prevent the bad nematodes (the ones that attach themselves to the root systems in plants that prevent the uptake of water and nutrients) by using bio-controls like fungi and bacteria that attack nematodes. Adding chitin, which is found in the shells of crustaceans like crabs, to the soil can promote the growth of a fungus capable of killing nematodes. Eco Poly 21 and Clandosan are two products that contain chitin
Neem oil can kill nematodes, as can crushed up sesame seeds or sesame seed oil. Dragonfire and Nemastop are two products that contain sesame seeds that control nematodes. Other soil amendments like oilcakes, sawdust, sugarcane bagasse, and bone meal are also effective nematode killers.
Promoting healthy plants is the most important way to prevent nematode infestation. Drought, excess heat, excess water, or lack of nutrients can all stunt the growth of plants, harm their root system, and allow nematodes to gain a foothold. Preventing nematodes by using crop rotation methods, least toxic pesticides, minimum tillage, and by planting cultivars that are resistant to nematodes will help keep plants in your garden free from nematodes.