Determining which fungi are the cause of a problem in a particular field is key to managing seedling diseases because these fungi require different management treatments. This article describes how to identify fungal diseases in soybean. Other fungi cause minor problems. Pythium damping-off is the first seedling disease to occur in a growing season because this fungus prefers cold soil temperatures. Dead seedlings may be visible on the ground with infected plants killed before the first true leaf stage.
Plants often have a rotted appearance.
Leaves of infected seedlings are initially gray-green and then turn brown. A few days later, the plants die. Diseased plants are easily pulled from the soil because of rotted roots. If symptoms similar to those caused by Pythium occur when soil temperatures are warm or in late-planted soybean, the disease is more likely caused by Phytophthora . Another way to determine the causal fungus is to check for stem rot.