Answer: It sounds like you are pretty certain that nematodes are the problem and just need the "clinical proof" of seeing the roots. You can try to nurse the tomato plants along by making sure they have plenty of water and frequent feedings. I recommend misting the leaves weekly with liquid kelp (available from Gardens Alive, 5100 Schenley Place, Lawrenceburg, IN 47025; ph# 812-537-8650). However, leaving the plants in place may encourage a higher concentration of nematodes to harrass the next crop. At season's end, pull up the plants and inspect the roots. If you aren't able to see nematode damage, you can have your extension service diagnose the problem (the ph# 213-744-4854). They will need soil and root samples, so give them a call and find out how to collect a sample for them. Next year, choose a nematode resistant tomato variety (the healthy plants you have may be resistant!), and grow the plants in a different part of the garden. Your extensions agent can also suggest a crop rotation schedule that may help you cut down on the concentration of nematodes in your soil. But keep growing those marigolds, because they do help to some degree!
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