Seed may decay prior to germination with infected seed becoming soft and rotted. Seedlings can also be killed before they emerge through the soil surface or just after they emerge. Areas of brown discoloration and soft, watery rot develop on infected hypocotyls and cotyledons. Infected seedlings wilt, collapse and shrivel up. Over time, infected or dead seedlings become dry and stringy or shredded.

Crusting, hard pan layers, herbicide injury, deep planting, poor seed quality, hail damage, insect damage, mechanical injuries, poor fertility or other factors that delay germination and emergence favor the development of Pythium seed decay and damping-off. To reduce losses from Pythium seed decay and damping-off, plant good-quality seed with a good germination rate under good seedbed conditions, minimize or avoid stresses that delay germination and emergence and use an appropriate fungicide seed treatment.