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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!