Good luck......there is nothing available to the homeowner to kill nemotodes. You are on the right track with raised beds and fresh sterilized soil.

Root Knot nematodes are the bane of us Southern gardeners. There is no effective chemical control for home use.

Solarization can be effective It takes something like 6 weeks to clear the top 6" of soil and lasts a few months. See - http://edis.ifas.ufl.edu/in856

Most veggy gardeners that I know grow resistant varieties or grow in pots. The pots are sunk into the ground so that the roots access water and nutrients by growing though the drain holes. The plant is generally strong enough to survive the nematodes by the time it grows through the drain holes. New potting soil every year. Use the old potting soil to enrich surrounding soil. Nematodes prefer poor soil with little organic matter.

Go hydroponic.

Larry