Larry,

Do you have sandy soil? That tends to be where nematodes get out of control because they can move around in the air space between the particles of soil. I have mostly dense red clay, and it all sticks together with little to no air space between the soil particles, so I've never had nematodes here. However, people who live near us that have sandy soil have huge issues with nematodes. Also, soil that is low in humus and organic matter has more trouble with nematodes than soil that has adequate levels of organic matter.

Most people here where I live use the Elbon Rye, and they use it every year, to combat the nematodes. I don't know anyone who has used anything else. Often with plants promoted as natural bio-fumigants, you have to plant so thickly that you cannot grow anything else but the bio-fumigant. Another technique that often works is to double the size of your garden, and let half of it lay fallow, solarizing it under plastic, every year, alternating from year to year with the two halves of the garden plot.

Nematodes can appear at any time. They can come in on purchase plants, on tools used in another area, on soil clinging to your shoes, etc. I understand they even can be carried in water when it runs off from one area to another. When you have them in one area, it is important to hose off your tools and shoes before you enter a nematode-free area so you do not inadvertently spread the nematodes around.

Elbon rye works because it traps the nematodes inside its roots and they cannot reproduce, so they die. I am not sure if the plants promoted as bio-fumigants work in the same way, or if they are more of a repellent.

We have one narrow band of sandy soil that lies mostly outside the garden because it is where the large pecan tree grows. Our second year here, I planted the nematocidal marigolds thickly in the band of sandy soil, hoping that if there were any nematodes there, the marigolds would get rid of them. That was the first year I planted anything there, so I don't even know if there were any nematodes there prior to that, but there haven't been any since. Since then, I have regularly added organic matter every year and the sandy soil is more of a sandy loam and I grow 4 o'clocks and other flowers in it just outside the veggie garden fence.

The nematocidal marigolds I planted were grown from seed purchased from Seeds of Change. They still carry it, so I've linked them below in case you want to read what they say about them.
Dawn

Here is a link that might be useful: Nematocical Marigolds at Seeds of Change

Dawn, thanks.

I feel I have covered the nematode bases pretty well. I never expected to get nematodes here. I add organic matter each year. My soil test in this garden is listed as "Clay" soil, although I feel it has more silt than I would really like.

I am about ready to till most of my fall garden in and plant more rye because I will get more organic matter from the rye, and I am running out of time to get good germination and growth.

The "Fumigant" crops seem to work by releasing a chemical from their cells. I am not sold on this idea yet, but you still get organic matter, which I am sold on.

I have more greens, lettuce and onions than I need. I am in good shape for next year. I have a good heavy rye cover crop that the deer are loving. My soil is wetter than I like, but my soil is usually too wet or too dry. I have too many rootknot nematodes and too many fungus gnat larvae that I will have to deal with by whatever method I can. That is the reason I was kicking around the Bio-fumigant Idea. At this point it looks like BTi and Elbon rye are up to bat.

Larry

Larry,

I overseeded the acre around the house with annual rye grass, and the deer and rabbits are loving it too. I also planted a deer forage mix in two places, and if they don't devour it all, I'll rototill it into the ground in the late winter or early spring.

It sounds like you are in great shape for winter.

I don't really understand the nematodes in your soil either, except you mentioned silt. They may be living in the silt in a similar manner to the way they live in sand. I know that nematodes thrive in hot summers. Maybe you need a cool, wet summer, but that would encourage more fungus gnats.

Since the rain started falling in September, it has been pretty wet compared to what it was like all summer long, and we have tons of flies, mosquitoes and buffalo gnats everywhere. I rely on Bti to keep mosquitoes from hatching in our ponds, and only 1 pond has water in it despite the rain, so the skeeters must be hatching out in water someplace else and then coming here to eat me alive.

The downside to the nematocidal marigolds was that they grew more like a aggressive wildflower than a sedate bedding plant. They were about 6' tall and made billions of seeds. The flowers are small and not at all showy either. I was pulling up those tiny seedlings for 3 or 4 years every spring and I have a feeling if I were to rototill that soil now, I'd have a billion more seedlings sprout from buried seeds suddenly exposed to light.

Dawn