They probably came with that plant if you bought it and didn't spread to the others soon enough to show enough damage, but no doubt they have spread throughout the bed.

There are nemicides that you can buy, but I don't know what the long term affect on the soil is. Solarization of the soil is the recommended treatment. Spread compost on the soil and cover with plastic. You need lots of hot sun to fry these vicious little worms. I know solarizing the bed will lose you valuable growing space, but maybe you can rig up some pots to replace that bed.

wouldnt crop rotation help ?

ken

There are some organic products on the market, but none that are packaged for retail sale, as yet.

I doubt very much that your tomatoes were the cause of the nematode infestation. They were grown in a soil-less potting medium, in little containers, just like you would at home. The potting mix isn't re-used as it's all in the cell pack. Commercial potting mixes are considered sterile and free from pathogens. Unless you are purchasing your plants from a local source who grows their seedlings in the ground, there's little chance of bringing home nematodes with you.

Root knot and other plant parasitic nematodes are plentiful in soils all around the world. As you well know, root knot nematode is very commonly found to be a problem with tomatoes. Yes, it's the little French marigold varieties that appear to be most effective against those particular little guys, as well as some of the other pest species, too.

Treating an area with marigolds will require that you lose a growing season, unfortunately. At least in the location you wish to grow tomatoes or other nematode attractive plants. The marigolds have to be sown rather heavily, like a cover crop, over the affected area. The following season, that specific area should have a much, much lower population of nematodes and can be used safely. You don't have to put your entire garden area under a bed of marigolds (unless you want to), just that location where tomatoes, peppers, etc. are intended for future plantings.

Remember, you can't just plant a marigold fence around the tomatoes (darn it all), nor does scattering a few plants here and there (called intercropping) seem to be helpful. Intercropping, by the way, CAN be very useful in controlling early blight!

Nematodes travel, albeit slowly. You might need to treat that area again the following season. It's wise to move plants from one year to the next, and the same goes for the marigolds.

Soil solarization is something of an exacting procedure, but is successfully used for a variety of soil pathogens. Nematodes are more tolerant of heat than most of the other things that solarization may kill, but can still be helpful if done at the right time, the right way, and for as long as it takes for those critters to boil! There's sure to be lots of good information on the Web about how to get the job done, but if you have any trouble, let me know.

By the way, it might very well be worth your while to contact your local extension office about the rye grass (Elbon). There might be some local distributors, since it's an Oklahoma introduction.

It sure is worth some experimentation, and I know that I'll be trying it this year. I don't ordinarily grow marigolds because they need to be deadheaded so frequently, and they are SUCH a spider mite magnet.

SO, along with the usual housekeeping tasks to help keep early blight at bay, African marigolds might help to prevent infection, too.

One thing, though, just to clarify something. Though abamectin is a bacterium product, it should be used with the utmost caution. It is a broad spectrum pesticide, lethal to a wide range of beneficials including bees. There are abamectin products labeled for caterpillars, beetles, wasps, ants, and a wide range of other 'pests'. Even at normal rates, it has proven to be highly dangerous for many species of fish.

That makes it quite different from the Bacillus products commonly used to control caterpillars, beetles, or mosquitoes/flies/gnats.

I hope you find a good source for the ryegrass. Were you going to use it for a fall planting, spring planting? I saw that some of the usual seed houses were selling it, though I didn't notice if it was for last season or this year.