Is It Really Seedling Blight?

May 25, 2012 07:45 AM
Is It Really Seedling Blight?


Farmers across the Corn Belt are beginning to notice cases of seedling blight in their fields. Several appear isolated, with a few cases being widespread. Ken Ferrie, Farm Journal Field Agronomist says that each year it is common to walk a field and find a small amount of isolated seedling blight. If seedling blight seems widespread on your farm, keep these important factors in mind if considering replant.
To accurately diagnose if your crop is suffering from widespread seedling blight, you first have to understand how the disease develops. soil borne fungi that live in the ground year-round. While some seedling diseases come on the seed, most are
The disease’s fungi attack young corn that is still relying on the mesocotyl due to lack of root development, says Bob Nielsen, a Purdue Extension Agronomist. This year, he says, the disease is infecting young corn seedlings at a growth stage where the protective seed treatments have naturally deteriorated. The plants are particularly susceptible to the damaging effects of the disease on the mesocotyl because their primary root systems are not yet sufficiently developed to sustain and nurture the young plants.
In general, the infection attacks corn in cool, wet soils.
"Microorganisms are like us, they like the right temps and moisture to flourish," says Keith Diedrick, area agronomist for Pioneer Hi-Bred in Indiana. "That’s exactly what we saw in April, cold and wet periods for the infection to occur."
Neilson and Diedrick point out that blight outbreaks are dependent on timing of rainfall, seed treatment depletion and seed growth.
"Corn that is stressed is susceptible to blight," Ferrie says. "It could be stressed from soil crusting, cool temperatures, too little or too much water." 
He says the stars have to align for seedling blight to be majorly damaging corn this season.
"Blight as the cause of replanting corn is most likely going to be in low lying areas with little drainage. A situation where soils were saturated for 24-48 hours and Pythium had a chance to attack the seedling."
Ferrie says that if you’re in a situation where rain is prevalent and temperatures are cool, than its probably seedling blight. If the soils are dry, like they are in the southern half of Illinois, then seedling blight is possible but not likely, he says.
Dry soils causing poor crown root development leading to what’s referred to as rootless corn syndrome could be the culprit of the dying corn according to Ferrie.  
To accurately diagnose your fields Ferrie says you have to think about the disease triangle.
-          Do you have a susceptible crop?
-          Are conditions right for the disease to develop?
-          Is the pathogen present in the soil?
All three points of the triangle have to be right for massive disease damage to occur. Have you seen seedling blight in your fields? Join the discussion now!


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