Solarization is an important tool, but you'll need more to deal with rootknot nematodes effectively. Regular amendments with crabshells/chitin increase nematode egg parasitism on a microscopic level. Using resistant varieties and lots of French marigolds helps to starve them out. Quick cover crops of mustard chopped into the soil release a gas that kills some nematodes.

Organic growers I know on the Gulf Coast continue to grow susceptible crops like okra so they will know when nematode populations get crazy. Good luck!

I have a light nematode problem (they are there, but most affected plants seem fine). Freezing in winter helps, but in zone 10 that's probably not an option. I tried a resistant variety of tomato this year and was quite amazed at the difference when I pulled out the roots. Perfectly smooth, normal roots on the resistant varieties and knobbly messed up roots on the others (they all fruited fine). So an affirmation of the resistant varieties approach. Also I think adding more organic matter is recommended and I think there are nematode-attacking nematodes you can apply. I also remove affected roots when the crops are done, and either leave them to rapidly dry in the driveway (hot weather) or just trash them. Probably that's too much labor on a large scale, but no reason to leave them their chow/breeding grounds once I'm through with the plants.

Buying and spreading beneficial nems is an effective way of controlling the parasitic and RKN. Beneficial nems are available online from several organic amendment sources. Don't know if you can find them locally. Timing of the application is crucial.

Dave

I suspected on more than one occasion, it is RKN that is going to town on my beans. The plant starts to wilt, I water. The plant wilts more...I water more. Plant dies. Nothing left but a stem in the ground. I hate RKN.
My normal regimen of watering was every 6 or 7 days if anyone is wondering. I wasn`t overdoing it.

Actually, I've been thinking of trying beneficial nematodes for my onion maggot problem. I know there are different strains for different pests, and I haven't yet come across one that says it works against pest nematodes. Do you know which strain that is, Dave (or anyone)? Actually, I'm also wondering why different companies give wildly different application rates for them.