Frequent rains over the last three weeks have left many pockets of wet soils in fields. Plants may not have emerged from these low-lying areas yet, or if plants have emerged, stand may be uneven and seedlings are exhibiting reduced vigor. There are many reasons for poor emergence and stunted seedlings, including environmental stress, but seedling blights might also be to blame.

Seedling blights are prevalent when cool, saturated soil conditions persist after planting. These conditions favor germination and infection by many of the organisms that cause soil-borne diseases. Cool, wet soils also slow plant growth and development and give diseases more time to infect and damage the seedling.

Seedling blights are caused by a variety of soil or seed-inhabiting fungi. Infected seeds may rot after germination, preventing emergence, and plants that emerge have reduced root development and are often stunted. Roots of infected plants may be brown and discolored and can be soft or mushy. Infected plants may also have brown discoloration on the mesocotyl. It is difficult to determine in the field which disease is to blame for a specific case of seedling blight, and it may be necessary to submit a sample to get an accurate diagnosis.

The risk of seedling blight development decreases when crops are planted into warm, dry soils. These conditions allow seedlings to germinate and emerge rapidly. However, it is often necessary to plant into less than ideal soil conditions, and fungicide seed treatments provide some protection against seedling blights. Most corn is currently treated with a combination of fungicides that protect against both diseases caused by true fungi and fungal-like organisms, known as water molds. Replanted soybeans should be treated with suitable seed treatments that protect against fungal organisms (Fusarium, Rhizoctonia), and water molds like Pythium and Phytophthora.


Source:  Purdue University