Soybean cyst nematode
Description: Roundworm, about 1⁄25" long. Females are usually swollen and can be seen with the naked eye. Yellow to white in color. Larvae are less than 1⁄64" long. Eggs are contained in dead females, which are brown and lemon-shaped and appear as cysts on roots.
Timing of damage: V2 to R6
Type of damage: Plants will appear yellowed and stunted, usually in patches throughout the field.
Scouting: Dig up stunted plants and wash soil off roots by placing in a bucket of water. Check for female nematodes on roots. Then take a soil sample and send to a nematology lab.
Economic threshold: Varies. Ask a nematology lab or local Extension office for guidelines.