C.O.R.N. Newsletter 2010-27

Dates Covered: 
August 24, 2010 - August 30, 2010
Andrew Kleinschmidt

Soybean Sudden Death Syndrome – Popping Up in Many Fields this Summer

Some soybean fields have already started to turn as we come to the end of August.  Most soybeans are healthy and could use one more hit of rain.  Some soybean fields have patches of plants that are dying early, and the majority of these fields have Soybean cyst nematode (SCN) combined with the fungus, Fusarium virguliforme, which causes sudden death syndrome (SDS).  These two have been associated with each other, since this root pathogen was first identified in the US.  This fungus will colonize the roots and cause a root rot, which leads to decaying roots.  When soil is damp, the blue spores of the fungus can be found on the tap roots.  While this fungus is working on the roots, it also produces a toxin which causes the yellowing, browning and early defoliation of the leaflets. 

There are several factors that contribute to how severe SDS can be in a field.  High SCN will contribute substantially to the yield loss associated with SDS and how early defoliation will take place.  On heavy soils, compaction is also playing a role.  The compacted areas of fields, headlands or where some land was worked when it was too wet, all maintain moisture and cooler temperatures during the spring than better drained fields.  Wet, cool conditions favor this soil borne fungus.  Research in Iowa shows that planting soybeans when soils are cool and then wet favor the development of SDS.  Other studies in Southern Illinois, demonstrated that deep ripping of no-till fields could alleviate disease development.  We tried this several years ago, but the year following the field treatment, was too dry and hot for SDS to develop. 

The development and severity of SDS can be reduced by improving drainage and choosing varieties with high levels of resistance.  This is another disease, that is a bit of a challenge to breed and screen for resistance, but much progress has been made in the past five years.  Southern Illinois University at Carbondale has the most extensive resistance screening program in the US, their results for each year are posted http://soybean.siuc.edu/.  A very good piece on SDS is currently available from the North Central Soybean Research Program site at http://www.planthealth.info/. Check the bottom right side of the website.

Management of soybean cyst nematode is becoming more and more critical.  In addition to direct yield loss, contributions to the increase in severity of root diseases caused by other fungal pathogens is becoming more apparent.  Monitoring of SCN numbers is going to become more and more important as we continue to produce soybeans in Ohio.

Incomplete ear fill may also be related to kernel abortion. If plant nutrients (sugars and proteins) are limited during the early stages of kernel development, then kernels at the tip of the ear may abort. Kernels at the tip of the ear are the last to be pollinated and cannot compete as effectively for nutrients as kernels formed earlier. Stress conditions, such as heat and moisture stress, nitrogen deficiency, hail, and foliar disease damage, may cause a shortage of nutrients that lead to kernel abortion. Periods of cloudy weather following pollination, or the mutual shading from very high plant populations can also contribute to kernel abortion. Some agronomists and farmers characterize the kernel abortion that occurs at the end of the ear as “tip dieback” or “tip-back”, although poor pollination is also usually a factor affecting poor kernel set at the tip. Kernel abortion may be distinguished from poor pollination of tip kernels by color. Aborted kernels and ovules not fertilized will both appear dried up and shrunken; however aborted kernels often have a slight yellowish color.

 Tip Dieback

Image Caption: Tip Dieback

Is the presence of barren tips a major cause for concern? Not always. In many cornfields this year, favorable growing conditions may have resulted in a larger number of potential kernels per row than normal. So even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal. The presence of ears consistently filled to the tip may actually indicate that a higher plant population is needed to optimize yields.

Another ear development problem getting attention involves ears with missing kernel rows (usually on the side of the cob away from the stalk that give sort of a zippering look on the ears”).  The zippering often extends most of the cob’s length. The zippering is due to kernels that are poorly developed and/or ovules that have aborted and/or not pollinated. Affected ears are often associated with corn plants which have experienced drought stress during early grain fill; cobs associated with the zippering are usually smaller than normal and poor tip fill is usually present. Differences in the degree of zippering among hybrids are evident. What’s difficult to explain is why this very distinct "missing row" anomaly occurs on the outside or underside of the ears fairly consistently.

 Zipper Ear

Image caption: Zipper Ears

Some of the explanations for zipper ears that I’ve heard include the following: 1) silks attached to the kernels (associated with the missing row) were covered up by other silks and simply did not get pollinated or, more likely, were pollinated late and as a result were more prone to abortion; 2) differential corn rootworm beetle silk clipping and feeding, i.e. beetles are below the ear during daytime hours, preferentially clipping silks of kernels facing downward? 3) differential kernel growth rate on the ear. Under drought stress, silk emergence can be slower than pollen shed. Perhaps silks on the outside or underside of the ear emerge more slowly than those facing the stalk? As a result, they may be pollinated later or emerge after pollen shed is complete. The later pollinated  kernels may be outcompeted for limited photosynthates by other kernels which are larger and further along in development, and thus more effective in competing for the limited supply of photosynthates (similar to the problem that occurs with kernel abortion that occurs at the tip of the ear - "tip dieback"). 4) Small, short ear shanks might play role in this problem - if the shanks collapse or pinch (due to drought) perhaps it might impair the vascular tissue conducting nutrients to kernel rows on the outside or underside of the ear.

In studies in which corn plants have been subjected to severe defoliation during the late silk and early blister stages, we’ve observed the resulting ears to show zippering, which suggests that a sudden reduction in photosynthate supply may be a factor. The zippering did not occur when plants were subject to similar defoliation at the milk or dough kernel development stage.

For more on ear development problems, including images, check the following:

Nielsen, R.L. 2009. Effects of Stress During Grain Filling in Corn

Available at http://www.kingcorn.org/news/timeless/GrainFillStress.html

(URL verified 8/23/10)

Thomison, P. and A. Geyer. 2007. Abnormal corn ears. Ohio State University Extension. ACE-1. available at  https://agcrops.osu.edu/specialists/corn/resources/of-interest/AbnormalCornEarsPoster_000.pdf/view  (URL verified 8/23/10)

Potential Soybean Pod and Seed Feeding Bean Leaf Beetle Injury

Potential Soybean Pod and Seed Feeding

As we are getting into the R5-6 growth stages of soybeans where the seeds are developing, we would remind growers of possible pod and seed feeding injury by various insects.  The usual ones considered problems in Ohio are the bean leaf beetle and grasshoppers.  Although bean leaf beetles did not seem that common during the most of the summer, we are now seeing some moderate to high second generation in some fields.  Growers are advised to monitor their fields for these two insects, and are reminded that there is a fact sheet on bean leaf beetles at http://ohioline.osu.edu/ent-fact/pdf/0023.pdf.  This concern is especially important with fields that stay green in September because of late plantings.

In addition to those two insects, growers might want to keep a watch out for stink bugs.  We have received reports of some fields in Ohio with higher than usual densities.  In a northern location, most the them appeared to be mostly the brown stink bug, although they sometimes appear green while they are immature.   In southern Ohio, you might also expect to see the green stink bug.  According to recommendations out of Purdue, the threshold for treatment is set at 4 stink bugs per 10 sweeps and the pods are still green, which indicates that the field in question is over threshold.  Stink bugs penetrate the pods with their mouthparts and then remove seed fluids resulting in possible discolored, deformed, and/or small beans.  Thus, if stink bugs are common in your fields, you should take multiple 10-sweep samples and count the number of bugs in each.  Greater than 4 stink bugs per 10 sweeps suggest that you should consider treatment.  We would recommend that growers across all of Ohio check their fields.  Many of the insecticides labeled for soybean insects will have stink bugs on their label.  However, take note of the pre-harvest interval (PHI) given on the label as we are getting within a month or so of harvest.  Many of the insecticides have as high as a 45 day PHI which might cause problems at this time of year.  These longer PHI’s should also be taken into consideration if the bean leaf beetle is a problem.

Five Important Management Steps to Profitable Wheat Production in Ohio

The 2010/2011 winter wheat season is fast approaching and as growers make preparations for planting, we would like to remind them of a few management decisions that are important for a successful crop. Nearly every farm in Ohio has a field or two that could benefit from planting wheat, if for no other reason than to help reduce problems associated with continuous planting of soybeans and corn. Consistent high yields can be achieved by following a few important management guidelines. Below are listed the most important management decisions that Ohio wheat producers need to make at fall planting time to produce a crop with satisfactory economic returns.

ONE. Select high-yielding varieties with high test weight, good straw strength and adequate disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have resistance to the important diseases in your area.  Depending on your area of the state, you may need good resistance to powdery mildew, Stagonospora leaf blotch, and/or leaf rust. Avoid varieties with susceptibility to Fusarium head scab. Plant seed that has been properly cleaned to remove shriveled kernels and treated with a fungicide seed treatment to control seed-borne diseases. The 2010 Ohio Wheat performance trial results can be found at (http://oardc.osu.edu/wheattrials).

TWO. Plant after the Hessian Fly Safe date for your county. This date varies between September 22 for northern counties and October 5 for the southern-most counties. Planting within the first 10 days after this date minimizes the risk of serious insect and disease problems including Hessian Fly, aphids carrying Barley Yellow Dwarf Virus, and several foliar diseases. Planting before this date has lowered yield by 7 to 20% in research trials due to disease and insect problems. On the other hand, planting late (generally after Oct 20 in northern Ohio) can reduce the number of primary tillers that develop in the fall and increases the risk of cold temperature injury. The Hessian Fly free dates can be found at (http://ohioline.osu.edu/iwy/flydates.html).

THREE. Optimum seeding rates are between 1.2 and 1.6 million seeds per acre.  For drills with 7.5 inch row spacing, this is about 18 to 24 seeds per foot of row with normal sized seed. When wheat is planted on time, actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging. There is no evidence that more seed is better, it only costs more money. If planting is delayed to more than three weeks after the Fly-Free date, plant 24-26 seeds per foot of row which is 1.75 million seeds per acre.

FOUR. Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure planting depth is uniform across the field. No-till wheat into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground.  Shallow planting is the main cause of low tiller numbers and poor over-winter survival due to heaving and freezing injury. Remember, you can not compensate for a poor planting job by planting more seeds; it just costs more money.

FIVE. Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development. Wheat also requires at least 45 ppm of available phosphorus per acre in the soil to produce really good grain yields.  If the soil test indicates less than 40 ppm, then apply 80 to 100 pounds of P2O5 at planting. Soil potassium should be maintained at levels of 135, 165 and 185 ppm for soils with cation exchange capacities for 10, 20, or 30, respectively. If potassium levels are low, apply 60 to 100 pounds of K2O at planting. In Ohio, limed soils usually have adequate calcium, magnesium and sulfur for wheat. Soil pH should be between 6.5 and 7.0.

The key to a successful wheat crop is adequate and timely management. The above recommendations are guidelines that may be fine-tuned by you to fit your farming operation and soils. They also assume that you are planting wheat in fields that are adequately drained. You can review more details on these, and other, research-based wheat management recommendations on-line at http://ohioline.osu.edu/iwy/

Harvesting and Storing Corn Silage

Several important decisions regarding corn silage harvest must be made in the next few weeks and these decisions will affect the dairy herd for the next 12 months.  Corn silage that is made and stored correctly is an excellent feed and one of the cheapest sources of nutrients in the Midwest.  On the other hand, silage that is not made correctly can adversely reduce milk production when fed to cows and will have lower nutritional value resulting in higher supplementation costs. 

The decisions that must be made (in order of importance) are:

  1. When to chop the corn
  2. Everything else

The “Everything else” category includes cutting height, chop length, kernel processing, use of inoculant, and how long the silage should be left before feeding.  Although these are important, if the silage is not harvested at the correct stage, these other factors will not overcome the problems associated with either immature or mature corn silage.

When should the corn be harvested?

Corn silage that is chopped too early (i.e., too wet) often undergoes a poor fermentation that results in higher fermentation losses and can reduce intake when the silage is fed.  Seepage also can occurs which reduces nutritional value and can cause environmental problems.  On the other hand, wet silage usually does not heat or mold during feed out and digestibility can be high.  Corn chopped too late (i.e., too dry) undergoes a limited fermentation resulting in a substantially less stable silage.  It often heats and molds at the silo face, during feedout, and in the feed bunk, and fiber and starch digestibility can be low.  The ideal dry matter (DM) for corn silage is between 30 and 38% depending on the storage structure (closer to 30% for bunkers and closer to 38% for uprights).  Slightly wet silage is usually better than slightly dry silage so err on the side of chopping early if necessary.  Dry-down rates vary substantially because of hybrid and weather but ON AVERAGE   corn plants gain about 0.5% units of DM each day after dent stage (can range between about 0.3 and 1% unit).  Dry matter should be measured; do not rely on kernel milk line to make harvesting decisions.

How high should the plants be cut?

The least digestible part of the corn plant is the stalk. It has high concentrations of neutral detergent fiber (NDF) and lignin. When cutting height is increased, more stalk is left in the field which reduces the proportion of corn silage that is stalk and increases the proportion that is leaves and ears. Typical stubble height for corn is 4 to 6 inches and most of the research on high cut corn had stubble heights of 15 to 18 inches. The absolute certain response will be a 4 to 6% reduction in DM yield (this means a 4 to 6% increase in production costs).  Usually NDF concentrations are reduced and starch and DM concentrations are increased by 2 to 4 percentage units when corn plants are cut high.  However, milk production studies have failed to show consistent benefit.  Because of the certainty of lost yield and the uncertainty of any positive response, I do not recommend this practice.

What is the correct chop length?

Fine chopping promotes good packing and increases the rate of fermentation in the silo, but fine chopping may result in silage that does not promote adequate chewing when fed to the cow. Coarse chopping may cause fermentation problems and can increase sorting when fed to cows. Chop length has been described as the theoretical length of cut (TLC) at which the chopper was set, but TLC is a poor descriptor of actual particle size of the silage. A better approach is to actually measure particle size at the time of chopping with a device such as the Penn State Particle Separator. Corn silage that had not been kernel processed with 3 to 6% of the silage on the top screen and 60 to 65% on the second screen (8 mm hole diameter) of the Penn State Separator usually ferments well and has good nutritional value. For processed corn silage, a very wide range in particle sizes (equivalent to approximately 2 to 21% on the top screen) had no effect on cows.  If the processing rolls are set properly (i.e., most kernels are physically damaged), silage with 5 to 10% on the top screen is adequate. Particle size evaluation should be done during harvest so that adjustments can be made.

Should kernel processing be used?

Proper kernel processing is when most of the kernels are physically damaged which results in improved starch digestibility for kernel processed silage than conventional silage. However, the response is a function of the maturity of the corn plant and hybrid. Processing almost always increases the nutritional value of drier corn silage (but it is still not as good as silage made at the correct DM) and is a recommended practice.  Processing silage made at the correct DM usually has a positive effect but the effect is much less than what is observed for dry silage.  Processing immature corn can substantially decrease its energy value and is not a recommended practice.  Chopped material should be visually examined during the harvest and if many undamaged kernels are observed, the processing rolls and/or chop length needs to be adjusted.

Should I use an inoculant?

The two types of inoculants for corn silage are lactic acid bacteria (LAB) and bacteria that produce acetic and propionic acid (bacterial species is Lactobacillus buchneri).  Treating corn with LAB usually reduces fermentation losses because it ferments faster and has more lactic acid (and less acetic acid).  On the other hand, L. buchneri increases acetic acid which increases fermentation losses but because acetic acid is  inhibitory to yeasts and molds silage treated with L. buchneri is extremely stable during feed out which reduces storage losses.  Conversely, silage treated with LAB often has reduced stability during feed out.  The return on investment of LAB is usually slightly positive if feed out losses are not a problem.  If spoilage and heating during feedout has been a problem or if silage feed out rate will be slow (less than about 6 inches/day) and/or the silage will be fed in the summer, L. buchneri could be quite useful.

How long should the silage be left undisturbed after filling?

Most studies with corn silage show that pH and acid concentrations become stable by 7 to 14 days post-ensiling if the silage is left undisturbed.  Yeast and mold counts may require up to 60 days before stabilizing and opening a silo will increase that time. The digestibility of corn silage can continue to improve even after months of storage.  Letting silage ferment undisturbed for several months has many benefits, however, maintaining silage inventory is not free.  The best compromise is to let silage ferment undisturbed for 1 to 2 months before opening.  This means that the first year you will need to harvest 13 or 14 months of silage and you need a place to store the silage that will not interfere with silo filling.

Pricing Standing Corn for Silage Harvest

How to price corn for silage as a crop standing in the field is a perennially challenging question.  The optimal answer will vary depending on your point of view.  Are you buying or are you selling? 

This corn silage pricing discussion is based on a corn crop standing in the field.  The owner’s goal is to recover the cost of producing and harvesting the crop plus a profit margin.  Their base price would be the price they could receive for the crop from the grain market less harvest/drying/storage costs.  Hopefully this would meet the goal of covering production costs and generating a profit.

To the grain farmer, the corn crop may have more value than just the income from the sale of grain.  If the crop is sold as silage, the corn fodder is no longer available as ground cover and/or as a source of some nutrients and organic matter.  This creates a potential opportunity for the dairy to provide some nutrients and organic matter back to the corn fields from subsequent manure nutrient applications.

To look at the value of the corn as silage, we can estimate that a ton of corn silage, on average, contains ~7 bushels of corn.  If corn is worth $3.70 per bushel, then the standing corn for silage would be worth about $26 per ton before the cost of harvesting for grain, or between $23.50 and $24.50 per ton depending on yield, assuming a grain harvest cost of ~$40 per acre.  This is a value for corn silage at 35% dry matter.  Prices also have to be adjusted for different dry matter concentrations.  If actual dry matter was 30%, then the value is about $20/t (i.e., 30/35 = 0.85 x $23.50/ton) Corn chopped at more than about 38 % DM or less than about 30% DM may not ferment properly and can be a problem.  The price for this corn silage should be discounted.

At the 2009 Tri-State Dairy Nutrition Conference, Normand St-Pierre reviewed the difference between valuing corn silage using the 7 bushels of corn per ton method plus harvest and storage costs and an adjustment for 10% fermentation loss, versus pricing based on prevailing feed nutrient value (Sesame) pricing method.  This method values the silage at what its nutrients are worth based on a wider selection of feed prices plus the harvest and storage adjustments.  The ratio of the two methods for 2005-2008, was 1.27.  In other words, the nutrient value of silage to the cow was potentially worth up to 27% more than value based on the market price for corn.

The SESAME value for Ohio corn silage is available in the most current edition of the Buckeye Dairy News available online at http://dairy.osu.edu.   Remember that this is the nutrient value for corn silage delivered to the cow, so harvest, storage, moisture, shrink and risk costs must be deducted from the SESAME value.

So, what does this mean in the real world?  The 7-bushel method is a good starting point.  There could be additional feed value to the buyer which has to be balanced against the harvest and fermentation risks that the buyer is assuming.

 The last factor affecting the value of standing corn is risk.  A farmer purchasing standing corn is assuming risk (will it ferment properly? can it be harvested at exactly the right time? what will the final nutrient content be? etc.).

The price for the standing crop should be discounted to recognize these risks.  What is the right amount to discount?  This is not an easy question and is one of the factors to consider when buyer and seller are negotiating a final price.  Setting the final, fair price for corn silage rests on an understanding of the needs of both the buyer and the seller and negotiating a price that ensures a reasonable profit for both.

Finally, it is critical that both parties agree on price, payment method and timing, crop measurement, restrictions, and similar details before the crop is harvested!  Ideally, the agreement should be in writing and signed by both parties.  These agreements are especially important when large quantities of crops (and money!) are involved.  While this type of contracting may be uncomfortable for some producers, mainly because they aren’t used to conducting business on more than a handshake, it forces the parties to discuss issues up front and can minimize troubling misunderstandings after harvest.

This article adapted from “Pricing Standing Corn for Silage” 2005.  Shoemaker, Weiss, St-Pierre and “Economical Value of Corn Silage, St-Pierre, Tri-State Dairy Nutrition Conference 2009.

Weather Update

Not much change from last week. A few cooler days to this week but next week into early September will remain much above normal overall for temperatures.

High this week will be in the 70s and 80s and lows in the 50s and 60s from north to south. Some areas of 40s are possible Thursday and Friday AM. We will be going back to 80s and 90s for highs this weekend and next week with lows in the 60-70 degree range.

Rainfall is forecast to continue below normal as discusssed last week into early September. After today, a few showers this week on Wednesday otherwise no rain is expected into early next week. Maybe something later next week. Expect the crops to brown up in a hurry.

Bottomline forecast: warmer and drier than normal next 2-3 weeks on average.

GVM Field Day

The annual GVM Field Day will be held on September 1, 2010 from 8:30 AM to 3:00PM. Fertilizer and pesticide application equipment, various software, light bars and much more are showcased at this event where ride and driving of the equipment is also an option. Commercial and private pesticide application and CCA credits hours will again be offered at this field day held at 4341 Sand Hill Road, Bellevue, Ohio 44811. Call 1-800-848–8460 to register for this free program. The entire program with a listing of available CCA and PAT credits is available at: http://crawford.osu.edu



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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.