C.O.R.N. Newsletter 2012-37

Dates Covered: 
October 30, 2012 - November 6, 2012
Editor: 
Curtis Young

Stalk Lodging and Ear Drop Impact Corn Yields

The heavy rains and strong winds (plus snow in some areas) forecast this week increase the potential for stalk lodging and ear drop, which could impact yields and slow grain harvest.

The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel/acre.  An average harvest loss of 2 kernels per square foot is about 1 bu/acre.  According to an OSU agricultural engineering study, most harvest losses occur at the gathering unit with 80% of the machine loss caused by corn never getting into the combine.

In the past, European corn borer (ECB) tunneling through ear shanks played a major role in causing ear drop.  The widespread planting of Bt ECB resistant hybrids has minimized this problem.  Reports of ear drop this year have been associated with drought stress and specific hybrid genetics.  Drought stress and high temperature conditions resulted in premature ear shank deterioration that promoted ear drop.  Certain hybrids are more susceptible to ear drop under such stress.  In an OSU research study conducted at 10 locations in 2011 and 2012 involving a comparison of three hybrids, we observed no ear drop in 2011, whereas in 2012 year ear drop was readily evident in one of the three hybrids at all locations.

In order to minimize ear drop losses in problem fields, some seed companies are recommending that farmers run their corn head as high as possible while adjusting ground and header speed for maximum ear retention.  Operating the corn header higher than normal may reduce the loss of ears flying out of the header during harvest.

Fields exhibiting ear drop and stalk lodging should be harvested promptly.  The presence of ear drop and stalk lodging probably outweigh economic benefits of field drying.  By late October to early November, field dry‑down rates will usually drop to 1/4 - 1/2% per day and by mid-November, probably 0 ‑ 1/4% per day.  By late November, drying rates will be negligible.

 

Preventing Field Fires During Harvest Season

No matter the ambient weather and field conditions, farmers are at high risk of having a field fire during harvest season.  

The conditions present during harvest season include dry plant material and grain dust that is highly combustible.  Hot equipment or engine sparks are great ignition sources.  Add high wind and there is a perfect opportunity for a field fire.  

Being prepared to handle field fires is important for all workers and transport drivers.  Combines, tractors, grain trucks, and pick-ups should all be equipped with a trustworthy fire extinguisher as the first lines of defense.  Combines should carry an ABC 10-pound fire extinguisher, while tractors and trucks are recommended to have a 5-pound unit.  These extinguishers should be in EACH vehicle in the field.  Nothing is worse than watching the combine go up in flames while you're running to the end of the field to retrieve the fire extinguisher on the grain cart.  Having an extinguisher on each piece of equipment ensures you will be ready to react on the first signs of smoke.

Don't get caught with a false sense of security.

If you follow the recommendations and own enough fire extinguishers, then you must also follow the maintenance recommendations.  Check the pressure gages periodically, making sure the needle remains in the "charged" zone.  If a unit has been partially discharged, it must be fully recharged before using it again.  Even a slight discharge can create a gap in the internal seal of the extinguisher valve, causing the pressure to leak out.  The pressure needle may linger in the charged zone; however there may not be adequate pressure to expel the contents.

Extinguishers should also be inspected periodically by a fire professional.  Fire service companies can be found in the yellow pages of most phone books.  Your local fire department or insurance company can also point you in the right direction for service companies.  Some extinguishers are not designed to be refilled, or are too old to be refilled.  These units should be replaced when they expire.  Having these old extinguishers around does no good when the time comes to pull the pin.

Follow other fire prevention practices.

It is also important to keep machinery in good repair.  Apply grease to bearings and oil chains regularly to reduce friction.  It is recommended to perform maintenance checks at the end of the day, rather than at the beginning, to detect any hot smoldering areas that may break out into flames overnight.   

Keep machinery clean and free from plant materials, especially around the wrap points.  Wipe up any fuel or oil leaks to eliminate additional fuel sources; and do not leave oily rags on equipment or in the cab.  

Take time to cool down the equipment each night, and check for any hot spots.  These steps can make a difference to save equipment, facilities, commodities, and lives.

Being prepared to handle field fires is important for all workers.  Having machinery equipped with a trustworthy fire extinguisher is one of the first lines of defense.

Be fire smart, and safe harvesting.

 

Sampling for SCN - Why It Is Important

While it is still fresh in your mind, many of you probably noticed the great deal of variability this year in yields that occurred as you were driving the combine across the field.  Part of the variability is due to the presence of soybean cyst nematode (SCN).  Why is it important to know where it is and what the levels are?  Here are a few reasons: 

1.  Yield losses can be huge when SCN populations are high and susceptible varieties are planted.

This year in some of our trials, we have documented yield impacts of 100% when susceptible varieties were planted into fields with high levels of SCN.  The presence of SCN and the drought really hammered some plants this year.

2.  SCN tends to sit in pockets, especially in no-till production systems - so knowing where to sample is important

 From our North Central Soybean Research Program funded project we have been able to grid sample numerous fields over the past 5 years.  From this exercise we have also been able to show how variable SCN is in fields.  Within a 25' span - we can go from undetectable levels to over 2,000 eggs/cup of soil.  This level is where we begin to see measurable yield losses.  Monitoring a field and noting where yields are low is key and those are the places to target soil samples to begin with.  Long term monitoring of the location and the size of the infestation to be sure it doesn't grow and get out of hand.

3.  SCN is adapting to some of the sources of SCN resistance.

We have found, in Ohio, some populations that like to feed on the roots of plants that have the genes from the primary source of resistance, PI 88788.  We don't know how widespread this is, but it does mean that if you have been planting SCN resistant varieties, then you all must be sure to monitor SCN as well.  You are not off the hook from soil sampling.  If the populations in your field have adapted, you will see an increase in SCN populations over time - not a decline.

4.  Rotation might not be working as well as it should.

We have visited some fields in Ohio over the past 3 years where SCN is a major problem.  These are fields where SCN populations got above the 10,000 eggs/cup of soil or greater.  The producers did the right thing and rotated out of soybeans for 3 or more years.  Replanted again with a resistant soybean and got hammered again.  When we took samples from these fields, the numbers were still too high.  This phenomenon has been observed by both Greg Tylka at Iowa State University and Terry Niblack when she was in Missouri.  We have some SCN populations that are really only interested in feeding on soybeans and they will wait until the field is planted. 

5.  Best management practice overall - is to keep those populations low and don't let them get above the 5,000 eggs/cup of soil mark.  It's a lot easier to keep low populations low than it is to reduce high populations!

This can be done with rotation - rotation - rotation - keep the numbers low by planting non-hosts (corn, wheat and alfalfa); keep weeds under control in the fall and spring that might add another cycle of reproduction; and plant varieties with the best SCN resistance package.  If SCN populations stay below this level then hopefully we will not end up in a situation like number 4.

6.  So sample - target the areas where you saw the yields drop, plants were stunted or they matured early than the rest of the field.  They tend to be the hot spots.  Note the size of these areas in the fields and continue to monitor them.  But also remember that SCN can reduce yields significantly without causing any visible symptoms.

Here is a rough guideline:

-- If your populations come back as non-detectable (0) - and you have a good 3 crop rotation (corn, wheat, soy) and you do not plant a double crop - sample for SCN every 20 years.

-- If your populations come back as non-detectable (0) and you have wheat in your rotation but you double crop - sample for SCN every 10 years.

-- If your populations are non-detectable (0) and you plant corn/soybean - sample every 10 years

-- If have SCN populations of 40 to 2,000 - and you rotate corn/soybean/wheat - sample every 5 years

-- If SCN populations are 40 to 2,000 and you only plant soybeans - sample EVERY year

-- If SCN populations have gotten out of control in the past (>2,000) - sample EVERY year

Finally, fall is the best time to sample.  It gives time for the labs to process them so you can make the best decision for choosing your variety for next year. 

The following labs all process soil for SCN:

OSU C. Wayne Ellett Plant and Pest Diagnostic Clinic, 8995 E. Main St. Bldg. 23, Reynoldsburg, OH 43068, 614-292-5006, http://ppdc.osu.edu

Brookside Laboratory Inc., 308 S Main St., New Knoxville, OH 45871, Phone: 419-753-2448, FAX:  419-753-2949, http://www.blinc.com

Geophyta Inc., 2685 CR 254, Vickery, OH 43464, Phone:  419-547-8538, FAX:  419-547-8538,

nathan@geophyta.com

Spectrum Analytic Inc., 1087 Jamison Rd. NW, Washington Court House, OH 43160, Phone:  800-321-1562 or 740-335-1562, FAX:  740-335-1104, http://www.spectrumanalytic.com

 

Fall Populations of Soybean Aphids Non-Existent

As anticipated, soybean aphids were at extremely low levels in 2012; indeed, most growers saw no aphids at all.  We have been sampling buckthorn in the fall of 2012 to determine the overwintering levels of the soybean aphid.  These observations are to determine if we can make a prediction as to the potential for problems in 2013.  Normally in late summer of a low aphid year we would expect an increase in aphid numbers and a move to buckthorn in the fall.  However, we have seen no soybean aphids, either individuals or eggs, on any of the buckthorn that we have sampled throughout the state.  The lack of aphids is also the norm across the Midwest.  Thus, at this time, we are holding off any predictions for this coming summer although the possibility exists that next year might break the two-year low/high aphid cycle.  Growers should plan on monitoring the situation closely next year, and read the C.O.R.N. newsletter for details.

Late Autumn Hay Harvesting and Grazing

The drought this year has left most livestock producers with very short forage supplies, so many are cutting hay fields this autumn regardless of the calendar or weather forecast.  Hay harvesting across Ohio the past few weeks has led to questions about management guidelines and the impact of late cutting or grazing on forage grass and legume stands.  The biggest management concern is with legume stands.

When significant regrowth occurs after a fall cutting of tall legumes (alfalfa, red clover, birdsfoot trefoil), energy reserves in the roots and crowns will be depleted and there may not be sufficient time for their replenishment before a killing frost.  This is often the case with cuttings made the first 10 to 12 days in October.  Fall cutting dates that allow only a short regrowth period will leave the plant in a lower energy status going into the winter.  Energy reserves are important for winter survival and regrowth early next spring.  This is why we recommend the last cutting be taken early enough (early September) to allow at least 6 weeks of fall regrowth so energy reserves can be built up to a high level going into the winter.  An alternative is to delay fall cutting until a time when regrowth will no longer occur, although this is not recommended on heavier soils.  The best way to ensure no fall regrowth is to cut after a killing frost.

A killing freeze for alfalfa or red clover is generally defined as temperatures of 24 - 25F over a period of at least 4 hours.  A lesser freeze event may burn the top of the plant, but growth will still continue from the green, unburned leaf area below.  However, the short day length and lower temperatures going forward from this point in time should prevent substantial regrowth from occurring.  So we would expect there to be little regrowth when cutting or grazing during the last few days of October into early November, even if a killing freeze has not yet occurred.

So, does this mean that all the alfalfa we have seen around the state that has been cut before a killing frost is going to die over the winter?  While some stands will indeed be hurt by fall cutting, other stands will not, or they will be impacted in a minimal way.  That is because there are other factors that play a role in determining winter kill.  We have already mentioned the role of cutting date in the fall as a factor in winter injury risk (and degree of regrowth that occurs), but there is less winter kill risk when a fall cutting is taken on a young vs. an old alfalfa stand, and less risk when the stand is planted on a well-drained site.  In addition, stands where good soil fertility has been maintained, especially with good levels of soil potassium and a soil pH close to 6.8 will have reduced risk of winter kill.  Growers who use improved varieties with good disease resistance and winter hardiness will have reduced risk of winter injury.  Finally, cutting frequency during the season can play a role in the effect of a fall cutting.  The more frequent the cutting, the more chance there will be for winter injury from cutting during the fall; so a fifth cutting taken in the fall will have much higher risk of winter injury than a third cutting taken in the fall.

There is one important exception to the safety of making a very late fall harvest when regrowth would not be expected.  That exception is for heavy soils prone to shrink/swell cycles that can result in heaving of taprooted legumes like alfalfa.  Late fall cutting results in lack of residue cover that leaves the soil more exposed to the prevailing air temperatures.  So the soil will be more susceptible to freeze/thaw cycles and will substantially increase the risk of heaving damage.  A study on a Wooster silt loam soil showed that cutting alfalfa in early November resulted in heaving of 50% or more of the stand compared with less than 10% heaving where no fall cutting was made.  A late cutting of alfalfa or other taprooted forages is only recommended on well-drained soils that are not prone to heaving events.

Sometimes the question is asked if too much top growth can lead to smothering out of the stand over the winter.  For alfalfa this is not an issue because the leaves will dry up following a killing freeze, become brittle and drop off the plant.  The stem that remains standing is not a concern for smothering the stand.  Tall grass plants, however, can mat down, providing a favorable habitat for disease development that could thin out the stand.  For this reason, it is recommended that a grass hay field with tall growth be cut or grazed before winter.  This is especially a concern for perennial and annual ryegrass; those stands should be cut to 2 - 3" going into the winter.  

With our shorter days and cooler temperatures it becomes very difficult to get a cut legume or grass to dry down enough to bale as dry forage.  Wrapping wilted forage or harvesting as haylage is the best mechanical option. 

Grazing a hayfield is usually a more economical option as compared to mechanical harvest at this time of year.  Use of temporary electric fencing can facilitate the grazing of a hayfield.  While forages such as alfalfa, clovers and cool-season perennial grasses do not produce toxic compounds after a frost, bloat can be a concern when alfalfa or clovers are grazed after a frost.

The risk of bloat is higher one to two days after a killing frost.  The safest management practice is to wait a few days after a killing frost before grazing pure legume stands.  At that point the forage will begin to dry down from the frost damage.  If animals are not accustomed to grazing high legume content stands or when grazing the stand before a killing frost, it is a good idea to fill them with dry hay before turning into the legume field.  Move animals into the legume field in the late morning or early afternoon after they have been grazing another pasture so that they are not entering with an empty rumen.  Maintain access to dry hay or corn stalks while grazing alfalfa, or swath the alfalfa ahead of grazing and let the animals graze the dried forage in the swath.  Bloat protectant compounds like poloxalene can be used effectively if fed to animals in a way that ensures consumption of the compound in sufficient and uniform quantities each day by each animal.  Finally, when grazing alfalfa stands, restrict grazing when soils are firm to avoid treading damage to the plant crowns.

 

 

 

 

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.