Answer: Pest nematodes are very difficult to get rid of. (Don't confuse these with the beneficial nematodes you can buy to help control grubs, among other pests.) The best solution is to grow types of vegetable and flowers that are not affected by nematodes in the soil where the nematodes have been found to be a problem. If you have another area to plant a garden, that may be a place to try to grow plants that are attacked by nematodes.
You can also grow plants that have been shown to reduce the number of nematodes in the soil. In the fall, plant 'Elbon' cereal rye and allow it to grow over the winter. Then plow it under in the spring. Nematodes enter the roots of this tall grass-type plant and cannot survive. Follow this during the warm season with a solid (not just a few plants) planting of French marigolds throughout the garden area as marigolds are another nematode 'trap crop.' These plants will not kill all the nematodes, but will reduce their numbers significantly.
Finally, rototill the soil in the dry, hot days of summer and allow the surface to totally dry out for a week or so. This will kill nematodes in the upper dry layer. Repeat the rototilling and drying steps several times if possible to destroy even more nematodes.
Q&A Library Searching Tips