Those microscopic unsegmented roundworms live in practically every environment in the world but only a few nematodes can kill your plants.
There are good and bad nematodes. Some of the good ones eat bacteria and fungus and prey on some insects pests. The bad nematodes are plant and animal parasites.
When a plant is infected, you will see the plant wilting, turning yellow, smaller or thinner than other similar plants, or the plant just die.
3 Basic types of harmful nematodes:
Nematodes on the outside of the roots.
They eat the roots of your plants and you cannot tell they are there except by the plant getting sick or dying.
Root Knot nematodes.
These small worms get into the roots of plants and interfere with the proper functioning of the roots which either weakens or kills the plant. You can recognize them by digging up the roots and looking for hard little knots on them.
Nematodes in the stem or leaves.
Some get into your plant and stay in one place; others move around the plant causing damage as they go. It’s very hard to tell they are there even after the plant is dead.
Laboratory soil sample analysis is the only way to determine if a nematode infection is present and may be necessary to identify the most effective control measures.
Using a lot of organic matter in your plant beds will help prevent the nematodes from migrating to your plants but unfortunately, once there are nematodes in your soil the only solution is replace or solarize your soil.
The solarization process is as follows:
Clean all the plant matter and debris from the area.
Place two layers of clear plastic over the soil and place a divider such as a 1” plastic pipe between the layers.
Seal the edges of the plastic with soil.
Let the sun beat down on the plastic and soil for a couple of months.
This process will kill pretty much everything in the soil down to the depth of about one foot. Plants or turf can now be re-introduced to the area.