Corn Seedling Emergence Problems.php

In Ohio we have widespread concerns with replanting corn, especially the corn that was planted during the April 15 through 20th time period, just before the 4 to 5 day period of cold rain and snow. Soil temperatures dropped from near 60 degrees F on May 20 to near 40 degrees F by May 25. Soil temperatures did not get back to the 50 degree F level until about May 3. There are several problems associated with corn emergence:1) soil crusting limiting shoot emergence, 2) cold injury to germinating seeds causing severely retarded germination and seedling growth and seedling death, 3) saturated soils slowing soil warm up and inhibiting growth, and 4) seedling disease causing seedling death. One or more of these problems are affecting plants in fields. Initial surveys of affected fields last week (May 10 to 14) indicated significant damage resulting in dead seeds and dying seedlings where radicals were brown and mesocotyl tissues had disease lesions. Many of these young seedlings died over the weekend. This week it is evident that surviving plants are growing slowly and plants beneath crusted soil continued to make some progress due to more favorable soil moisture and temperatures. Seedlings that have developed nodal roots from the node immediately above the mesocotyl will likely survive and grow normally especially if the mesocotyl is white and nodal roots are white indicating no further disease development. Seedlings that are not as far advanced, but have a few new white lateral seminal roots originating near the radical are showing signs of progress. If the soil temperatures continue to rise and with moderate soil moisture these plants are also likely to survive and grow. As indicated, the temperature and moisture levels over the next week or so will have a large impact on the crop. Growers are advised to assess fields by digging up the plants to assess root and mesocotyl health. Replanting should be done now in fields with low plant populations due to dead and dying plants. Progress of surviving plants can be assessed over the next few days. In many cases seedling emergence varies greatly within fields. It is important to dig plants and evaluate seedling growth and identify potential seed injury (if its present) before making final replant decisions.