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C.O.R.N
Newsletter
2005-12
May 9, 2005 -
May 17, 2005
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Check Corn Fields for Emergence Problems
by
Peter Thomison
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Although many fields in Ohio were planted to corn three weeks ago, corn emergence has been limited because of cool wet soil conditions. More recently, as soils have dried, soil crusting has inhibited emergence. Unfavorable growing conditions have also resulted in other factors (such as seeding diseases) adversely affecting growth and poor emergence in corn. Given the potential impact these factors can have on stand establishment and the need to replant, I strongly encourage growers to make stand counts, scout fields, and troubleshoot emergence problems.
My counterpart at Purdue, Dr. Bob Nielsen, commented in his most recent newsletter article (May 8, 2005) that he had visited a number of fields in east central Indiana Friday afternoon that had not yet emerged even though the calendar was approaching three weeks since they had been planted. Bob stated that “apparent seedling disease development in these fields was widespread and eventual stand establishment may be poor enough to merit replanting.” He went on to observe that a common combination of factors among these fields was mid-April planting (5 to 6 days prior to the recent cold snap) followed by the onset of cold soils (too cool to sustain germination), heavy rainfall, short-term ponding, saturated surface soils, surface soil crusts [which sounds familiar to what many of our Ohio fields have experienced], and (eventually) seedling diseases.
Although corn has just started to emerge or has not yet emerged, growers should carefully inspect seedlings for symptoms of disease; especially in lower lying areas of fields where ponding and saturated soils were more likely. Bob noted in his article that the consequences of seedling disease on the success of emergence and initial stand establishment will become more apparent by the end of this week, if not sooner.
Bob’s article “Some Mid-April Planted Corn in Trouble” is available online at http://www.agry.purdue.edu/ext/corn/news/articles.05/StandLossDisease-0508.html and contains some excellent pictures of various symptoms of seedling disease development.
Diagnosing emergence problems early is critical in identifying solutions and developing successful replant plans, if needed. Here's a list of a few common things to look for if you encounter an emergence problem in corn this spring.
(I’ve adapted some of this information from a newsletter article by Dr. Greg Roth, my counterpart at Penn State).
-No seed present. May be due to planter malfunction, bird or rodent damage. The latter often will leave some evidence such as digging or seed or plant parts on the ground.
-Coleoptile (shoot) unfurled, leafing out underground. Could be due to premature exposure to light in cloddy soil, planting too deep, compaction or soil crusting, extended exposure to acetanilide herbicides under cool wet conditions, combinations of several of these factors, or may be due to extended cool wet conditions alone.
-Seed with poorly developed radicle (root) or coleoptile. Coleoptile tip brown or yellow. Could be seed rots or seed with low vigor.
- Seed has swelled but not sprouted. Often poor seed-to-soil contact or shallow planting- seed swelled then dried out. Check seed furrow closure in no-till. Seed may also not be viable.
-Skips associated with discolored and malformed seedlings. May be herbicide damage. Note depth of planting and herbicides applied compared with injury symptoms such as twisted roots, club roots, or purple plants.
-Seeds hollowed out. Seed corn maggot or wireworm. Look for evidence of the pest to confirm.
- Uneven emergence. May be due to soil moisture and temperature variability within the seed zone. Poor seed to soil contact caused by cloddy soils. Soil crusting. Other conditions that result in uneven emergence already noted above.
Note patterns of poor emergence. At times they are associated with a particular row, spray width, hybrid, field or residue that may provide some additional clues to the cause. Often two or more stress factors interact to reduce emergence where the crop would have emerged well with just one present. Also, note the population and the variability of the seed spacing. This information will be valuable in the future.
B) Assessing Corn Seedling Emergence and Seedling Diseases - Pat Lipps
Growers are encouraged to spend some time walking fields and digging seedlings to evaluate their condition before making replant decisions. Dig seeds from the seed furrows and wash them off with water. Seeds and seedlings that are brown in color, are soft and fall apart easily while digging are obviously dead or dying. Seeds and seedling roots or shoots that have a weft of white to pinkish mold growing on them are likely victims of fungal attack and will likely die. Pythium and Fusarium are common fungi that attack plants and cause these damping-off or seedling blight symptoms under wet, cool conditions. It is more difficult to diagnose disease damage on plants that also show abnormal growth caused by cold soil conditions or by crusting of the soil surface. Given a chance to emerge with warmer soil temperatures many of these plants will likely survive. It is best to check these seedlings very closely for dark brown or soft areas on seedling roots and on shoots next to the seed. These immature plant structures should be white to creamy white in appearance. Any discoloration will indicate a problem that could worsen if the soils remain cold or wet. Plants that show disease or damage will likely be slow to emerge even with warmer conditions and also show less vigor. Growers should also remember that uneven emergence and slow growth at this time of year could impact overall yield, but these effects must be weighed with the known impact of later planting on yield potential. A slight to moderate reduction in stand is a better bet than replanting in many instances, especially if you have to decide whether to replant these fields or plant fields that are not yet planted . Of course the later in the season the replanting is done the greater the risk of lost yield potential.
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cooperation with the U.S. Department of Agriculture,
Keith L. Smith, Director, Ohio State University Extension.
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