Hi Dave –
I have been told numerous times that Beneficial Nematodes will NOT work on Root Knot Nematodes. In fact the University of Florida states:
“Currently, no predators are commercially available for augmentative releases for nematode control in vegetable production systems.”
So, the question is; how do you control harmful “root-feeding” nematodes organically? Chemical nematacides are available, but very expensive, extremely toxic and not approved for organic use. I believe your best bet for getting rid of root knot nematodes in the garden is to combine several least-toxic strategies, which include the following:
โข Grow resistant varieties. Look for an “N” on the seed packet which indicates nematode resistant.
โข Avoid moving infected soil to other parts of your garden. Nematodes do not travel far, but can be spread with tillers and hand tools.
โขย Rotate garden crops with plants that are known to reduce nematode numbers. Broccoli and cauliflower have been mentioned as good rotation crops.
โข Soil Solarization — heating the soil with clear plastic prior to planting will reduce or eliminate many harmful organisms including nematodes.
โขย Build your soil with good organic soil amendments. Shellfish fertilizer (https://www.planetnatural.com/product/shellfish-fertilizer-50-lb/) contains chitin which encourages the growth of organisms that inhibit harmful pest nematodes.
Hope this helps!