Managing Nematodes

Nematodes belong in a pest category all their own. These parasites cause more than a billion dollars in damage as they attack roots. To identify nematode issues, start by scouting for stunted, wilted, yellowed or dead plants. Check with your lab and local resources for sampling protocol and economic thresholds.

Click here to download this checklist.

Corn: Lance Nematode

  • Visible only under a microscope, lance nematodes feed from inside and outside of the corn roots.
  • Timing of damage will be early spring, but the nematodes can be active throughout the season.
  • These nematodes cause the most damage in sandy soils.
  • Scout a month after planting and before soils warm up.


  • These nematodes are small transparent parasites that are visible only under a microscope.
  • Most damage occurs mid-season, but lesion nematodes can be active throughout the growing season.
  • Lesion nematodes feed inside of the roots, so root samples are necessary. Be careful not to expose samples to high temperatures.


  • This transparent parasite measures about ¼’’ but can only be seen under a microscope.
  • Needle nematodes feed on root tips from the outside of the roots.
  • Scout a month after planting and before soils warm up.

Root Knot

  • This worm-shaped parasite is invisible to the naked eye and most active when soil temperatures reach 60°F to 65°F.
  • Roots of infected plants appear swollen or knotted.
  • Economic threshold varies with soil type. Ask nematology lab or local Extension office for guidelines.

Soybean Cyst Nematode

  • This roundworm measures about 1⁄25” long. Females are usually swollen and can be seen with the naked eye.
  • Eggs are contained in dead females, which are brown and lemon-shaped and appear as cysts on roots.
  • Damaged plants usually appear in patches throughout the field.



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