CORN Newsletter: 2005-13, May 16, 2005

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C.O.R.N Newsletter 2005-13
May 16, 2005 - May 24, 2005

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Corn Emergence Problems and Replant Decisions
by Patrick Lipps, Peter Thomison


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The rains over the weekend have promoted corn emergence in fields with surface crusting problems and have probably reduced the need to replant many fields. Nevertheless, replanting is expected to be extensive in parts of Ohio, with perhaps as much as 30 to 50% of some counties’ corn acreage affected, especially in northern Ohio.
Before finalizing replant plans, growers need to scout their corn fields and dig up seedlings to evaluate their condition. Some fields that were crusted over and exhibiting corn leafing out under ground last week may be showing signs of recovery following rotary hoeing and the weekend’s rain. Other fields may also appear to be recovering with seedling shoots visible above ground. However, close examination of such seedlings may reveal that seeds and roots are rotting, showing seedling blight symptoms, and likely to result in seedling death.

More on assessing corn emergence problems and making replant decisions is available in the following C.O.R. N. newsletter articles (http://corn.osu.edu/archive/)

“Assessing Corn Seedling Emergence and Seedling Diseases” (Pat Lipps) and “Check Corn Fields for Emergence Problems” (Peter Thomison) C.O.R.N. Newsletter 2005-12, May 9-17, 2005.

“Corn Replanting Considerations” (Peter Thomison) C.O.R.N. Newsletter 2005-11, May 3-10, 2005.

Reports of the corn seedling emergence problem indicate that the worst fields were planted on or after April 15. During this time, the soil was relatively dry and soil temperatures were increasing to the mid 60 degree F range. On April 20 cold rains started that lasted until April 25. Over this 5 day period soil temperatures dropped from 60 degrees F to about 40 degrees F at most locations in the state. Cool temperatures during the last week of April kept soil temperatures below 60 degrees F until about May 3. Therefore, germinated seedlings and seeds were under persistent cold and wet conditions for at least two weeks in most locations.

Damage from cold temperature stress adversely affected the germination of seeds and the growth of young seedlings and probably predisposed the plants to invasion by soil fungi capable of causing seed rot and seedling blight. In addition to slowing the germination process, cold temperatures, snow and freezing rain from April 20-25 may have caused irreparable harm to the delicate structures of emerging corn seedling. When dry corn seed absorbs cold water as a result of a cold rain or melting snow, “imbibitional chilling injury” may result. Cold water can cause similar injury to seedling structures as they emerge during germination. Such injury in corn seed ruptures cell membranes and results in aborted radicles, proliferation of seminal roots, and delayed seedling growth. When temperatures remain at or below 50 degree F after planting (as they did this year for two weeks) damage to germinating seed is particularly severe. Many of the corn seed planted shortly before the cold temperature stress of April 20-25 have produced seedlings exhibiting symptoms which are characteristic of imbibitional chilling injury (e.g. stunted or aborted radicles).When this physiological damage is combined with surface soil crusting, saturated soil conditions, compacted soils, deep seed placement, and seedling blights, you have a recipe for widespread emergence problems.

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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