Root-knot Nematode

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Root-knot nematodes cause enlargement or swelling of soybean plant roots. The visible symptoms include stunting, yellowing and wilting of the plant.
Reduced yields and premature plant death can occur. Warm, moist conditions favor hatching of eggs inside infected plant roots.

Root-knot nematodes are plant parasites that enter the roots of host plant to feed. This feeding causes the roots to enlarge.
Female adults may lay 500 to 1,000 eggs, which hatch if moisture and temperature levels are high enough. This plant parasite invades the roots of soybean plants, feeds and reproduces. This activity causes swelling of the roots into knot-like nodes.
Unlike nitrogen-fixing nodules that grow on the sides of healthy soybean roots, the root-knot nematode causes the actual root to enlarge.

Plant-feeding nematodes go through 6 stages: an egg stage, 4 immature stages, and an adult stage.
Many species can develop from egg to egg-laying adult in as little as 21 to 28 days during the warm summer months.
Immature stages and adult males are long, slender worms.
The mature adult females of some species, such as root knot nematode, change to a swollen, pearlike shape, whereas females of other species such as lesion nematode remain slender worms.
Nematodes are too small to be seen without the aid of a microscope.
It is believed that root-knot nematode survives from season to season primarily as an egg in the soil. After the eggs hatch, the second stage juveniles invade roots, usually at root tips, causing some of the root cells to enlarge where the nematodes feed and develop.
The male nematodes eventually leave the roots, but the females remain embedded within roots, where they lay their eggs into a jellylike mass that extends out through the root surface and into the soil.

Plant soybean varieties with tolerance to this pest and practice crop rotation with non-host plants to help limit root-knot nematode pressure.