Seedling Blight in Corn

June 8, 2000 7(12):74-75

Joe Lauer, Corn Agronomist

With all of the cool wet weather lately, we are beginning to pick up some Pythium seedling blight problems on corn. If a field seems to be "melting" back into the ground, it may have seedling blight. Confirm the disease by sending a sample to the Plant Diagnostic Lab.

An important question to ask growers is, "What seed treatment was used on the hybrid corn seed planted?" Companies use different products. Captan has been the industry workhorse since the 1950s. Maxim is a recent popular treatment used on corn seed. Both of these compounds are weak on Pythium, although Captan may be better at control than Maxim. A compound called Apron provides excellent Pythium control. Many companies have gone to Maxim+Apron or Captan+Apron combinations on seed treatments.

"Is there anything that can be done about the field now?"

Growers will need to wrestle with a stand loss decision (see Corn Replanting or Late-Planting Decisions UWEX Bulletin A3353).  Plant death will reduce stands. The difficult part of this decision will be to assess "plant health." If plants appear to be sick, only count as 1/2 of a plant. It may or may not eventually produce an ear. Look for poor growth; check the growing point for off-color and water soaked areas. 

If the decision is to replant, use the yield tables in A3353 for projected yields. It is still not too late to replant with soybeans.

If the decision is to leave the field, then watch the field closely next fall for stalk rots. It may need to be harvested early.

Table 1. Efficacy of seed treatments on common seedling diseases in corn.
Disease Captan Maxim Apron
Rhizoctonia GOOD GOOD POOR
Helminthosporium GOOD GOOD POOR
Penicillium GOOD GOOD POOR
Aspergillus GOOD GOOD POOR
derived from Pedersen, U. of Illinois

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