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:
• Grow resistant varieties. Look for an “N” on the seed packet which indicates nematode resistant.
• Avoid moving infected soil to other parts of your garden. Nematodes do not travel far, but can be spread with tillers and hand tools.
• Rotate garden crops with plants that are known to reduce nematode numbers. Broccoli and cauliflower have been mentioned as good rotation crops.
• Soil Solarization — heating the soil with clear plastic prior to planting will reduce or eliminate many harmful organisms including nematodes.
• 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!
Nematodes, nematodes, nematodes! Considering the nematode family constitutes one of the most abundant animal life on this planet, it should come to no surprise that nematode infestations are common. For fighting root knot nematodes with beneficial nematodes, the best time to apply the beneficials would be about 10-14 days before transplanting anything into the soil. Many of the recommendations for chemical nematode control involve organophosphates or carbamates (both effect nerve impulse transmission) and specialized equipment. I would recommend utilizing an integrates pest management approach instead of chemicals. Utilizing host plants which do not support nematode life, crop rotation, and choosing nematode resistant varieties are all steps you can take to rid yourself of those buggers once and for all.
Although root knot nematodes have a wide range of hosts, there are some crops that can help control the nematode population. Sudangrass and marigolds for instance, release chemicals into the soil that are toxic to nematodes, so they can be used as a cover crop. They can be grown outside of the regular growing season or instead of the tomatoes for a season. Perhaps a tomato -> marigold -> tomato -> sudangrass OR tomato -> marigold -> sudangrass -> tomato rotation would be ideal to combat the issue. This has an obvious setback since you won’t be producing tomatoes continuously, however with the implementation of other IPM practices you will drop your root knot nematode population to a manageable level.
Nematode resistant varieties recommend by Clemson University include:
Slicing: Better Boy, Celebrity, Park’s Whooper, Goliath
Paste: Classica, Viva Italia,
Cherry: Small Fry, Sweet Million
Check your local seed catalog for other resistant tomato varieties as well.
There are also a couple species of fungi in the Arthrobotrys order that has developed ways to prey on nematodes. These “nematophagous fungi” have two ways of capturing the microscopic worms. They can create structures with an adhesive that sticks to the nematodes and they can create noose-like structures that holds the nematode in place while the mycelium penetrates the nematode’s cuticle and devours the insides. (There are some sweet electronmicroscope pictures of that in this paper: http://www.tandfonline.com/doi/pdf/10.1080/21501203.2011.562559?needAccess=true&)
Good luck with your nematodes!