Don't understnd your comment of cross-pollination. If you're thinking it triggered a nematode infestation, it didn't.

Please show us your affected roots.

Perhaps the problem is clubroot.

Clarification: The seeds I planted were saved from last year's crop. May not be a pure mizuna strain, as would have been had I planted purchased seed. Therefore, its tolerance of root knot nematodes may be different than that of true mizuna. The cabbage (another RKN tolerant brassica) in this spot is much smaller than in other rows. I pulled one up, and it has root galls as well. Attached is a picture of the cabbage root. There was cucumber in this garden bed recently. The cucumber served as an ideal nematode host and was infested.

Well,f your soil has nematodes, the hard lesson is that you cannot seed directly into the ground. Instead, you must use transplants.

If you want to start your own plants from seed, you'll need to sow the seeds into containers filled with potting mix.

I start all my plants from seed, either directly in soil or transplants. Transplanting may help to give the plant a disease-free head start, but the stunted cabbage plant whose roots are seen above was a transplant. I just purchased bionem-wp , a bacillus firmus product. Will apply in spring once weather warms up (the nematodes are not active now in the middle of winter) Also going to incorporate other strategies such as crop rotation, vermicompost, and chicken manure. I sowed a large oat cover crop on some fallow land and will plant the susceptible crops there in spring. Small grains are good non-host plants for root knot nematodes.

That's interesting. Where do you live that you can obtain and use a product which is to be applied to commercial crops?

I live in Israel, in a moshav, a traditional a farming community. I bought this at the local agricultural supply store. If you live in the states though, everything (with the exception of chemical pesticides) is generally much more available than here. This particular product may be more available in Israel because it was developed here, by a company that was later bought by Bayer. It appears they hold a patent on bacillus firmus for nematodes, which may explain why I have not found other sources other than bionamgon from India. I haven't found it sold in the states when searching online. Last night I finally Opened the 10kg sack of this stuff. I put 100g in 4 liters of water, 300g sugar and a bit of agar and nutritional yeast. Molasses would have better, also yeast extract but this is what I have on hand. I am stirring it occasionally. Will then transfer either directly to ground via drip irrigation, or bubble it up in a bucket first. I am hoping to get more bang for buck by multiplying the bacteria before application. This is roughly as prescribed by a professional biolo-control lab manager whom I consulted with. He recommended just 5 grams of inoculant per liter. Given the lack of sterile and precise lab conditions at my disposal, I choose to use more product to guarantee colonization. The nematodes are now dormant in winter, but I am still giving it one application now.

Thank you for the explanation. As far as I can tell, the product isn't available in the US.

I hope that you're successful but wouldn't be surprised if your experiment fails because you are tweaking so many of the instructions/guidelines.

There is no way to know if the experiment will fail, because I will also be applying this product, as directed on label, to the entire garden via the irrigation system on early spring, summer, and fall. All I did for now was to spot treat with a garden pail in the areas where I had pulled up plant roots that showed damage.

I am using this product mainly as a long term strategy, in an effort to neutralize this bacteria in my garden soil. This organism was originally isolated from soils in my country, so it should do reasonably well here.