Seedling Blight Symptoms Seen After Rain, Cool Weather
Kiersten Wise of Purdue University wrote a recent article for the Purdue Pest and Crop Newsletter discussing seedling blights (http://extension.entm.purdue.edu/pestcrop/2010/issue8/index.html). Below is Kiersten’s article with a few of my additions to reflect local situations:
Frequent rains over the last three weeks in this area have left many pockets of wet soils in fields. some of those pockets plant have emerged, but the 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.
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. Andy’s note: I have seen a few examples of these plants in corn — these plants with severely infected mesocotyls will not survive.
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.
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