Plants grow slowly, in erratic spurts, and are generally dwarfed in size. When you dig up a troubled okra plant, numerous swellings and galls are evident on the roots. Because root knot nematodes don’t move far in the soil without human help, neighbouring plants may be infected while those at the end of the row remain healthy.
Okra is highly susceptible to root knot nematodes, in part because it thrives in the same hot summer conditions that please nematodes. Good crop rotations prevent nematode build-up in many gardens, but root knot nematodes may be unavoidable in sandy soils in warm climates. To increase your chances of success, grow a summer crop of French marigolds, followed by a winter cover crop of oats, wheat or rye. Then try okra. Regularly amend soil with materials that contain chitin, such as seafood meal, eggshells, or shrimp hulls. In the soil, these materials feed microorganisms that chow down on chitin, including nematode eggs.
Pull up badly affected okra plants, lop off the roots, and dispose of the roots in the bin. Compost the rest. Mark the area where the troubled okra grew, and do not grow okra, celery or carrots there again. If plants are only slightly affected, they may make a crop if a deep mulch is used to keep the root zone cool and moist.