Announcing a nitrogen management webinar

On Thursday, March 30 beginning at 9:00 AM, I will present a webinar summarizing our recent N management research, which is funded by the Illinois Nutrient Research and Education Council (NREC) using fertilizer checkoff funds.

Topics will include the status of N applied last fall, a summary of results from our N form and timing studies over the past three years, and a look at how well soil N tracked through the spring can tell us if we need more N.

You may register for the Spring Nitrogen Management Webinar at:  https://attendee.gotowebinar.com/register/8090182749410833409 After registering, you will receive a confirmation email containing information about joining the webinar. One CEU of NM (nutrient management) CEU will be available.


Planting date for corn and soybeans in Illinois

Relatively dry weather in recent weeks throughout much of Illinois and an early start to fieldwork might provide the unusual opportunity this year of letting us choose corn and soybean planting dates instead of having to wait until it’s dry enough.

There are reports that some corn and possibly some soybeans were planted as early as February this year. The main motivation for such plantings is often the excitement that comes (or doesn’t) from having the crop survive “against all odds.” While that may be satisfying, it doesn’t offer much profit potential. If the crop survives it hardly ever produces yields as high as those from planting at the normal time, and planting very early affects insurability and can also increase the cost of replant seed.

In the warm, dry March of 2012, we planted one date of our planting date study at Urbana on March 16. The crop emerged uniformly and grew well until frost on April 11-12 killed the tops of the plants to the ground. About 75% of the plants survived and grew back, though, and to our surprise this planting also yielded about 75% as much as the April plantings. Most corn planted in mid-March in 2012 (about 5% of the state’s corn was planted by April 1 that year) had to be replanted.

Most people avoid taking insurance coverage risks by planting before earliest allowable planting dates under the federal crop insurance program. Those dates for corn are April 10, April 5, and April 1 for northern, central, and southern Illinois, and for soybean are April 24, April 20, and April 15 in northern, central, and southern Illinois.

Having the earliest insurable dates for soybean about two weeks later than for corn reflects what until recently we considered to be the greater danger from planting soybeans very early compared to planting corn very early. In fact, with better seed handling and treating today, soybean seed produces acceptable stands with mid-April planting about as often as corn does.

Contrary to what many believe, soybean is no more vulnerable to frost than corn after emergence. The only time we’ve seen soybean seedlings killed by frost is when it gets near freezing at the time the hypocotyl hook is exposed to the cold sky, before the cotyledons are pulled from the soil. This period of vulnerability typically lasts no more than a day or two; after the hypocotyl straightens and the cotyledons open, soybean plants are fairly cold-hardy. While corn plants have been considered safe from frost until the growing point is near the soil surface, we have seen corn plants killed by low temperatures (often below 30 degrees) even if they have only two or three leaves exposed.

The primary cause of stand loss in both crops is having heavy rainfall soon after planting. Stand loss from wet soils before or during germination is greater for corn when soil temperatures are low. For soybean, having warm soil under wet conditions speeds up the germination process and mean that seedlings run out of oxygen before emergence. But chances of having heavy rainfall soon after planting are not higher with early planting, and stand problems due to wet soils are as common with May planting as with April planting.

Between 2007 and 2016, we ran planting date studies for corn at a total of 22 Illinois site-years, and between 2010 and 2016, at a total of 26 site-years for soybean. There were four planting dates in each trial, ranging from early April through late May for corn and mid-April through early June for soybean. Data are expressed as percentage of the yield at the highest-yielding date within each site-year.

As shown in Figure 1, planting date responses expressed as percent of maximum yield within each site-year are surprisingly similar for corn and soybean across recent trials. Both crops showed near-maximum yields when planted in mid-April to early May, and yields dropped to 95, 91, and 86% as planting was delayed to May 10, May 20, and May 30, respectively.

Figure 1. Planting date responses over 22 corn and 26 soybean site-years in Illinois.

Figure 1. Planting date responses over 22 corn and 26 soybean site-years in Illinois.

What should we take from the fact that yields of both crops declined at about the same percentage rates as planting was delayed through May? The main message is that we need to give similar priority both crops in terms of getting them planted on time. For those with more than one planter, that may mean planting both crops simultaneously, as fields get ready to plant. Our long-held idea of planting corn first them starting to plant soybean requires rethinking and possible adjustment. At the same time, the penalty for late planting of corn is a little lower once we get to late May and into June compared to that for soybean, so in fields that stay wet longer, soybeans may still be a slightly better choice.

We also see from the data in Figure 1 that neither crop is likely to yield more when planted in early April than when planted in mid- or late April. If fields for both crops are ready to plant in central Illinois on April 6, there are two reasons to plant corn first: 1) it’s insurable; and 2) corn seed is somewhat better able to emerge at high percentage when planted early than is soybean seed.

On the other hand, we generally expect about 85% of soybean seeds and 95% of corn seed to establish plants, so corn can be a little more vulnerable to less-than-desired stands if conditions turn bad after planting. In neither crop, however, would dropping desired stands by 5 percentage points cost much yield.

Finally, we should take care not to be overly influenced by what happened in 2016, a season when growers reported much higher yields from early- compared to late-planted soybeans. Statewide, over the past 20 years or so, the average date by which we get 50% of the crop planted is about May 1 for corn and May 22 for soybean. It would be good if we could move both of those dates up some, and even better if we could move the two dates closer together. Still, with years like 2012 when planting was very early but lack of rain lowered yields by a lot, there’s little relationship between average statewide planting date and average statewide yield.

Most planting delays are due to wet soils, and so are more or less beyond our control. Mudding in either crop, especially in April, is usually a mistake, given the slow rate at which yields for both crops fall as planting is delayed into May, and given the prevent-plant provisions of crop insurance in effect. We should be diligent at starting to plant when all (not just soil) conditions are right, but there’s little reason to panic when planting isn’t as early as we’d like.


Nitrogen in February?

The unseasonably warm and dry weather we have had during February this year has a lot of people applying ammonia, and others considering it. This raises the question of whether or not February is a good time to apply NH3, and also the question about whether or not a nitrification inhibitor (N-Serve) should be included in late-winter applications.

We encourage waiting until soil temperatures are below 50 degrees before making NH3 applications in the fall, and then to use N-Serve to slow conversion of ammonium to nitrate. Although it was several days into November before soil temperatures fell to 50 last fall, most people were patient, and NH3 went on well. We have not had as much wet weather since then that we had in December 2015, but the soil was not frozen for very long in recent months, and tiles lines have been running for some time in most areas.

Along with Dan Schaefer of IFCA, we are working on an N-tracking study funded by the Illinois Nutrient Research & Education Council (NREC) that includes three on-farm sites in central Illinois. We applied 200 lb. N as anhydrous ammonia in late October last fall, both with and without N-Serve. Figure 1 shows the amount of N (ammonium plus nitrate) that we have measured in samples taken in November, December, and late January. These are averages across the three on-farm sites.

Soil N recovered following application of 200 lb. N as NH3 in fall 2016. Data are averages over 3 on-farm sites in central Illinois.

Soil N recovered following application of 200 lb. N as NH3 in fall 2016. Data are averages over 3 on-farm sites in central Illinois.

The variability over time that we see in Figure 1 is normal with such sampling; we can’t say with confidence that amounts recovered changed over sampling dates or with N-Serve. When we recover amounts of N close to the amounts applied like this, we take that as an indication that there hasn’t been a lot of loss of N to date. In fact, we recovered considerably less N in February 2016 than we had applied in fall 2015, but by April we were able to recover the amount we had applied, and by May, after mineralization had kicked in, we recovered more N than we had applied the previous fall.

The percentage of soil N present in the nitrate form is also important, especially this far in advance of crop uptake. As a negatively charged ion, nitrate is not held by the soil, and so it will move freely with water as water moves through the soil, including into tile lines. Figure 2 shows the percentage of the N amounts shown in Figure 1 that was recovered as nitrate. Like soil N, percentage nitrate is not a very precise number, but we can see that nitrate percentages have gone up some since the fall but do not seem to be changing very quickly, and that N-Serve might be slowing this conversion to a small degree. At the same time, with more than half of the N now in nitrate form, and with soil temperatures above normal now, it is likely that most of the fall-applied N will be nitrate by May, if not earlier.

Figure 2. Percentage of recovered N (from Figure 1) that was recovered in the nitrate form.

Figure 2. Percentage of recovered N (from Figure 1) that was recovered in the nitrate form.

Does this mean we should hold off applying if soil temperatures rise to the upper 40s or lower 50s in February? If soil conditions are good, I don’t see a good reason to wait. For those who prefer to wait, soils dry now means a better chance of being able to apply NH3 with good soil conditions later in the spring. Nitrogen applied as NH3 converts to ammonium quickly, and ammonium will stay in the soil where it was applied. Nitrification (conversion of ammonium to nitrate) is a biological process, and while its rate is low when soil temperatures are in the 40s, it is not zero. So the earlier we apply NH3, the greater the chance that it will be converted to nitrate by the time soils warm and the crop is growing in the spring. Using N-Serve will slow this conversion, and is likely to be as effective used with NH3 applied in February or March as it is when used with fall-applied NH3.

Whether or not the conversion of ammonium to nitrate is a negative depends on the amount of rain that falls between the time nitrate forms (which depends on time and soil temperatures following application) and when crop uptake of N starts in early June. In the spring of 2016, nearly all of the fall-applied N was nitrate by early May, while very little of the N following spring application of NH3 was nitrate; but without loss conditions, the N from both treatments was fully available to the crop in June. We did not see excessive loss of N in the spring of 2015, even though June was much wetter than normal. That’s in part due to the fact that May 2015 was not wetter than normal, so the N was there in early June, and the crop was able to take it up before it was lost. If we happen to get wet weather in April or May, there could be substantial loss of nitrate, whether we applied it last fall or we wait until April to apply.


February 28: Soil Fertility Seminar to offer continuing education

Soil fertility, crop production practices and environmental stewardship will be the foci of a Soil Fertility Seminar on February 28, 2017 in 18 different University of Illinois Extension county offices.

Presentations will be delivered through web conferencing from 9 a.m. to 2:30 p.m.

Topics and speakers will include:

  • Increasing importance of sulfur for field crops–Dr. John Sawyer, Iowa State University
  • Illinois NREC: What have we learned?–Dr. Robert Hoeft, Illinois Nutrient Research & Education Council
  • Managing Nitrogen to Improve Efficiency–Dr. Emerson Nafziger, University of Illinois
  • Tile Nitrate Loss: Effect of fertilizer N application method and cover crops–Lowell Gentry, University of Illinois
  • N and P retention as influenced by tillage and cover crops in a corn-soybean rotation–Dr. Maria Villamil, University of Illinois

Registration costs $50 per person, which includes lunch. Certified crop advisors may earn up to five nutrient management credits.

To view a list of participating counties, a detailed agenda and to register, please visit the Soil Fertility Seminar Webpage.

Please note that the registration deadline may vary by county.


Extension Bi-State Crops Conferences in and near Western Illinois

Newer and longer-term partnerships between personnel in Illinois and personnel in Missouri and Iowa have resulted in several bi-state crops conferences to be held during January 2017 in Western Illinois or Eastern Iowa.

 

Friday, January 6, 2017: Bi-State Crop Advantage Conference, Burlington, IA, 8:30 AM – 4:00 PM

Location: Comfort Suites, 1708 Stonegate Center Drive, Burlington, IA.

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register

 

Friday, January 27, 2017: Bi-State Crop Advantage Conference, Davenport, IA, 8:30 AM – 4:00 PM

Location: Rhythm City Casino Resort, 7077 Elmore Ave., Davenport, IA

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register.

 

Friday, January 27, 2017: Western Illinois-Northeastern Missouri No-till Crop Management Conference, Quincy, IL, 8:45 AM – 2:00 PM

Location: John Wood Community College, 1301 S. 48th St., Quincy, IL

Hosts: University of Illinois and University of Missouri Extension, Illinois and Missouri NRCS

More Information: Click here to access the flier.

Online Registration: Click here to register.


2016 SDS Commercial Variety Test Results Available

SDS Variety Report

This past growing season personnel from Southern Illinois University, Iowa State University and University of Illinois evaluated more than 580 soybean varieties from 22 seed companies in USB-sponsored sudden death syndrome (SDS) variety trials. The varieties that were evaluated ranged from the very early (MG 0) to late (MG V) maturity groups. Maturity groups were divided into early and late categories; for example, MG II was split into early (2.0 to 2.4) and late (2.5 to 2.9) categories in order to more easily monitor crop development and assess disease at the appropriate growth stage (Figure).

Figure. Aerial picture of the 2016 Commercial SDS Variety Trial at the Northwestern Illinois Ag R&D Center in Monmouth. The difference in variety maturity is evident in this picture. Moving left to right are varieties in Early MG II, Late MG II, Early MG III and Late MG III.

Figure. Aerial picture of the 2016 Commercial SDS Variety Trial at the Northwestern Illinois Ag R&D Center in Monmouth. The difference in variety maturity is evident in this picture. Moving left to right are varieties in Early MG II, Late MG II, Early MG III and Late MG III.

At one or more locations in Illinois and/or Iowa each variety within a maturity group category was randomly assigned to a two-row plot within a block (replication); each variety was planted in three replications. Production of the crop within these trials followed university Extension recommendations and was similar to soybeans produced in any Midwestern farm field with a couple of exceptions: 1) to provide a disease-favorable environment irrigation water (where available) supplemented rainfall, and 2) to increase the chance that germinating seedlings would be exposed to the pathogen, at planting time sorghum seed infested with Fusarium virguliforme, the fungus that causes SDS, was placed in-furrow.

Plots were monitored throughout the growing season for growth and development. At the R6 or full seed growth stage, disease incidence and severity ratings were collected for each plot. In each maturity group category, varieties known to have high levels of SDS resistance or susceptibility were included as ‘checks’. Sufficient disease in the susceptible check varieties was required in order for data from a particular trial to be included in the final report.

The final report is available for download here.

While the data may be of use to crop producers to use as a reference when making their 2017 seed selections or for crop advisors or seed company representatives to use when advising their clients, the final report is forthcoming with its limitations:

“Data presented here is from a single year at one or two locations. Varieties may perform differently in other environments.”

“Plots were not harvested for yield in this program because yield comparisons can be misleading from disease nurseries utilizing small plots. Accurate yield data for commercial varieties should be obtained from state variety trials.”


Registration is now open for the 2017 Regional Illinois Crop Management Conferences

Registration is open for the 2017 Crop Management Conferences. These regional conferences provide a forum for discussion and interaction between participants and university researchers and are designed to address a wide array of topics pertinent to crop production in Illinois: crop management, pest management, nutrient management, soil and water management.

Certified Crop Advisers can earn up to 8 hours of continuing education credit. Advance registration, no later than one week before each conference, is $100 per person. Late and on-site registration is $120. Dates and locations along with links to location-specific agendas and online registration are listed below.

Conference topics include:

  • Updating Grain P and K Removal Levels – Dr.  Emerson Nafziger, University of Illinois, Extension Agronomist, Department of Crop Sciences
  •  Crop Management Strategies for Leaner Times – Dr. Gary Schnitkey, University of Illinois, Extension Economist, Department of Agriculture and Consumer Economics
  •  Increasing the Odds of Success: Integrating Weed Management Strategies – Dr. Aaron Hager, Univ. of Illinois, Extension Weed Scientist, Department of Crop Sciences or Dr. Bob Hartzler, Iowa State Univ., Prof. Weed Science or Dr. Karla Gage, Southern Illinois Univ., Asst. Prof. Plant Biology
  •  Is record-setting weather the ‘new normal’? – Dr. Jim Angel, Illinois State Climatologist, Illinois State Water Survey
  •  Management Practices to Reduce Tile Nitrate Loading – Lowell Gentry, University of Illinois, Senior Research Specialist, Department of Natural Resources & Environmental Sciences
  •  The living soil: Crop management, organic matter and soil biology – Dr. Michelle Wander, University of Illinois, Prof. Soil Fertility & Ecology, Department of Natural Resources & Environmental Sciences
  •  Predicting Insect Pressure: Surveys and Web-based Tools – Kelly Estes, Cooperative Agricultural Pest Survey Coordinator, Prairie Research Institute
  •  New Bacteria to Perennial Fungi: Revisiting Crop Disease in 2016 – Angie Peltier, University of Illinois, Extension Educator

 

January 18: Mt. Vernon – Krieger/Holiday Inn Convention Center. Click here to view the Mt. Vernon agenda. Click here to register for the Mt. Vernon location. For more information, contact Angie Peltier: (309) 734-1098, apeltier@illinois.edu.

January 25: Springfield – Brookens Auditorium – University of Illinois-Springfield. Click here to view the Springfield agenda. Click here to register for the Springfield location. For more information, contact Angie Peltier: (309) 734-1098, apeltier@illinois.edu.

February 1:  Champaign – i-Hotel and Conference Center. Click here to view the Champaign agenda. Click here to register for the Champaign location. For more information, contact Dennis Bowman: (217) 244-0851, ndbowman@illinois.edu.

February 15: Malta – Kishwaukee College Conference Center. Click here to view the Malta agenda. Click here to register for the Malta location. For more information, contact Russ Higgins: (815) 274-1343, rahiggin@illinois.edu.

Mail-in registrations must arrive one week before each conference in order to take advantage of the advance registration discount. To download the mail-in registration form, click here.

 


Soil Nitrogen and N Management Following the 2016 Crop

The 2016 growing season has been a very good one for corn in Illinois, with the November yield estimate of 202 bushels per acre, slightly higher than our previous best of 200 bushels per acre in 2014.

In sharp contrast to the wet June of 2015, most of Illinois received below-normal rainfall in June 2016, with parts of western and southwestern Illinois receiving less than an inch for the month. With May rainfall close to normal across the state in 2016, the wet soils and N loss conditions that we saw over most of Illinois in 2015 never materialized in 2016.

2016 soil nitrogen and N response

In our N-tracking project funded by the fertilizer assessment (Nutrient Research & Education Council), we apply 200 lb. of nitrogen per acre as fall-applied ammonia, early spring-applied ammonia, fall ammonia plus spring-split UAN, or spring-split UAN. We then sample during the spring to see how much N remains in the top 2 feet of soil.

Averaged over three locations in 2015, sampling in mid-June and at tasseling recovered about 70 and 42 percent, respectively, of the amount of N applied as fertilizer. In 2016, we found a little more N than this –about 76 percent in mid-June and 47 percent at tasseling. Grain yield levels didn’t differ greatly between the two years, but more of the N needed by the crop was taken up by tasseling in 2016 compared to 2015. Yields were similar in both years, though, so having more N taken up by tasseling did not clearly lead to higher yields.

Warm soils and wet weather in December 2015 caused a lot of concern about loss of fall-applied N in 2016. We did not, however, find lower amounts of soil N following fall N applications than we found following spring applications in 2016. But there were some differences between the two years in how much of the N recovered was in the ammonium form (coming directly from ammonia application) and how much was nitrate. Nitrate can move in the soil and be lost.

In both 2015 and 2016, about 80 percent of the N recovered in early May following fall ammonia application was nitrate. Following spring ammonia application, 59 percent of the nitrogen was nitrate in early May in 2015, while in 2016 only 39 percent was nitrate. By early June, when N uptake by plants began, 80 to 90 percent of the recovered N was nitrate in both years, regardless of timing of application.

It’s clear from these numbers that applying ammonia in the fall versus spring did not have much effect on how well the nitrogen was protected by remaining in the ammonium form, at least by the time N uptake began. This suggests that N loss is tied more closely to conditions during N uptake (June) than to N fertilizer timing, although sidedressing ammonia, which we did not do in this study, would have increased the amount present as ammonium.

Most N rate trials are showing considerably less N needed in 2016 compared to 2015. This year, we’re often seeing yields leveling off at N rates of only 140 to 160 lb. N per acre, at yield levels between 200 and 250 bushels per acre. We think that this reflects both the large supply of N from mineralization of soil organic matter under the favorable conditions of May and June this year, and also the drier June weather this year that limited N loss and root damage. Another sign of a good supply of N from the soil was the delay in development of N deficiency symptoms in corn grown without fertilizer N. It was common in 2016 to see unfertilized corn in our trials remain dark green into mid-June, when the crop was 3 feet tall or taller.

Nitrogen in the soil this fall

One might expect that less N loss might lead to higher amounts of N left over at the end of the season. We aren’t seeing this in most cases. Dan Schaefer of IFCA took soil samples at the time of crop maturity at a number of on-farm sites, nearly all of these showed soil N levels of less than 6 or 7 ppm, which we consider to be baseline levels. We’re also finding low soil N levels in samples taken following harvest in our N-tracking trials. The only place we’re seeing elevated levels is at N rates considerably higher than those needed to maximize yield. Using too much N is never a good idea, and that was especially true in 2016.

Those who added N late in late vegetative stages this year in addition to normal rates applied earlier might well have ended up with more soil N than usual after harvest. A vigorous cover crop like cereal rye will take some of this up. But the low levels of soil N in fields with normal rates of fertilizer N may not have enough N to produce vigorous cover crop growth. Trying to “prime” cover crop growth by applying fertilizer N this fall will increase N uptake, but may not necessarily increase net uptake after subtracting the amount applied.

Despite slow cooling at the start of November this year, soil temperatures are now below 50 degrees over most of northern and central Illinois, and ammonia application is underway. Soils are mostly in good shape for this, but application should be delayed in fields with wet surface soils .

Nitrogen management for the 2017 crop

We can think of no good reason to adjust N rates, unless planned rates are substantially higher that the 175 (155 in northern Illinois) and 210 lb. N per acre or so calculated by the N rate calculator for corn following soybeans and corn following corn, respectively, in the region of Illinois where fall N is used. If planned rates are higher than this, a downward adjustment is in order. We never know what the spring will bring, but it makes more sense to react to loss conditions if they occur that to apply more N “just on case.”

If the plan is to apply some N in the spring after fall application, consider subtracting that amount from the fall application rate in order not to exceed the suggested rate. If 2017 is like 2016 with regard to N nutrition, using more than suggested rates will nothing to increase yields, but will increase both economic and environmental costs.

There’s been a lot of talk in recent years about how CEC “limits” the amount of N that should be applied to a given soil; the maximum amount commonly mentioned is 10 lb. N per unit of CEC. CEC is a measure of the concentration of negatively-charged exchange sites in a soil. Soils with more clay and more organic matter have higher CECs; silt loam or silty clay loam soils with 3 or so percent organic matter typically have CEC values between 20 and 40. That’s more than enough to “hold” the right amount of N.

There’s no sound basis for considering CEC a measure of “N-holding capacity,” any more than to consider it as potash- or calcium-holding capacity. One unit of CEC in the topsoil will hold 360 lb. of ammonium, so a soil with a CEC of 20 would have only 2.5% of its exchange sites occupied by ammonium if it were all on the exchange sites. Ammonia applied to soil dissolves instantly in soil water, then converts quickly to ammonium. Like any positively-charged ion (cation) in the soil solution, some ammonium ions quickly occupy exchange sites, and some stays in soil solution. Little if any ammonium does not move down in most soils, regardless of the amount applied (within reason.) A possible exception is light, sandy soils with very low CEC values. Nitrogen should not be applied in the fall in such soils.

So there’s no reason to be concerned about CEC values when it comes to applying N on the vast majority of Illinois soils. Instead, base N rates on the N rate calculator, which is based on research showing what rate can be expected to maximize profit. And then apply N responsibly in order to minimize N loss and to keep N for the crop.


Diplodia ear mold at harvest: What can be done now?

Producers in western and west-southwestern Illinois may have observed symptoms of Diplodia ear mold during harvest.

Figure. Healthy corn kernels (left) and kernels showing symptoms and signs of Diplodia ear mold have been found throughout the western and southwestern Illinois crop reporting districts and in corn harvested at the Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth.

Figure. Healthy corn kernels (left) and kernels showing symptoms and signs of Diplodia ear mold have been found throughout the western and southwestern Illinois crop reporting districts and in corn harvested at the Northwestern Illinois Agricultural Research and Demonstration Center in Monmouth.

 

Diplodia Symptoms and Machinery Adjustments at Harvest. Diplodia ear mold can cause lightweight kernels with a dull grey to brownish color and sometimes small black structures call pycnidia (Figure). The infected kernels are prone to breakage and can result in poor test weights, poor grain quality and fine materials in the hopper or grain bin. Adjusting combine settings can help to maximize grain cleaning and minimize breakage.

Figure. Kernels on ears that have symptoms of Diplodia ear mold may appear dull and more greyish than healthy kernels. Breaking an ear in half may reveal small black fruiting structures call pycnidia that are produced by the fungus that causes Diplodia ear mold.

Figure. Kernels on ears that have symptoms of Diplodia ear mold may appear dull and more greyish than healthy kernels. Breaking an ear in half may reveal small black fruiting structures call pycnidia that are produced by the fungus that causes Diplodia ear mold.

 

How Much is Out There? An informal survey of several grain elevators and farmers in Western Illinois had reports of less than 2 to more than 50% kernel damage from Henry to Madison County, respectively. Factors such as planting date, the timing of rain events after fertilization and hybrid susceptibility can result in a range of damage within the larger region and even within a farming operation.

Dockage at the Elevator. Further conversations with elevator and ethanol facility personnel suggested that the threshold for accepting damaged grain can vary depending upon the local market and end-use. The price at which a farmer can market grain begins to decrease for every percentage point of damaged kernels above 5% and some grain elevators will set a damage threshold above which they will not accept the grain depending upon the end use and how quickly the grain will leave the elevator.

It is important for those producers that encounter Diplodia ear mold to be in communication with their crop insurance agent. While the high yields expected this year may offset lower grain prices overall, those farmers with low sale prices due to a lot of dockage may be able to recoup some of their losses.

Stenocarpella maydis, the fungus that causes Diplodia ear mold, metabolizes the starches in corn kernels leaving them lighter weight than non-infected kernels. The ethanol manufacturing process uses bacteria to turn corn starch into simple sugars, eventually fermenting them to yield ethanol. Diplodia-damaged kernels can yield less ethanol and may be why elevators that supply ethanol plants may have a lower threshold (one mentioned 10%) for damaged kernels than others.

One positive is that unlike Aspergillus, Fusarium or Gibberella ear molds, Diplodia ear mold is not associated with a mycotoxin. However, regardless of whether infected kernels are in the field, in the combine hopper, semi trailed or grain bin, unless the grain is cooled and dried to below 15% moisture, the fungus will continue to grow and metabolize starches, lowering test weights and grain quality. Additionally, unless properly dried, the fungus can colonize uninfected kernels that are damaged during harvest or storage operations.

Drying and Storing Moldy Grain. With on-farm storage, many crop producers have the option to hold onto their grain to market it at a later time. Storing diseased grain separately and for only short periods of time is recommended to reduce the chance of additional losses.

Agricultural engineers from Iowa State University have produced several tools that can help those interested in learning more about just how long air drying may take with a given fan and grain bin size and the crop moisture and air temperatures outside. For those that have the ability to add heat to the drying process, these experts have also produced tools that can help in factoring all of the costs associated with drying with or without heat.

Here are resources related to these topics produced by Iowa State University Agricultural Economists and Engineers:

Grain Storage – Quality Management​:
Dryeration
Aeration
Fan Performance

Grain Storage – Economics:
Grain Drying Economics
Grain Storage Economics

General information about Diplodia ear mold and practices to help reduce disease risk in future corn crops can be found here.


Corn Earworm, European Corn Borer, Fall Armyworm, or Western Bean Cutworm: Which One Is Causing the Injury I’m Finding on My Corn Ears?

Several questions about injury on corn ears has made it way to my desk the past week.


Insect injury to corn ear (photo courtesy of Duane Frederking).

Damaged ear tips, missing kernels, and fungal pathogens are all being reported. Several insect pests in Illinois could be the culprit. Corn earworm, fall armyworm, European corn borer, and western bean cutworm are pests of Illinois cornfields. Their larvae all feed on the ears of corn plants.

So how does one determine the cause of ear damage this late in the season? The answer is simple: You really can’t. At this time in the season, it is rare to find any larvae still feeding on corn ears. Without larvae, you can’t be positive if injury was caused by earworms, corn borers, fall armyworms, or bean cutworms, as they cause very similar injury. Let’s look at each insect individually.

Corn earworm. Two generations of corn earworm infest Illinois cornfields each year. Because earworms generally do not overwinter in Illinois, summer populations arise primarily from immigration of moths from southern states in late spring and early summer. Infestations of earworm larvae can cause injury to corn plants, including slight defoliation of leaves, damage to the tassel, and consumption of silks and kernels. The second corn earworm generation usually occurs during pollination. Larvae enter the ear primarily through the silk channel, unlike European corn borer and fall armyworm, which enter through the husks or cob. As silks dry, corn earworm begin feeding on kernels. Larvae feed at the tip and along the sides of the ear near the tip, continuing to feed until they mature. At that time the larvae drop to the ground to pupate. When leaving the ear, corn earworm may drop from the ear tip or create exit holes by chewing through the husk. These exit holes can be mistaken for entrance holes caused by other larvae.


Corn earworm larvae.


Corn earworm injury to corn ear.

European corn borer. Two to three generations of European corn borer occur in Illinois each year. Injury to corn ears is caused by the second and third generations. Loss of grain to larvae’s direct feeding on kernels has not recently been an issue in field corn, but in sweet corn and seed corn, losses can be significant. We’ve also received reports of corn borer feeding in non-GMO corn. Larvae feed on pollen and silks before entering the ear. Entry to the ear is also gained by tunneling through the shank and cob. Ear feeding by corn borer larvae is not focused on any one area. Injury can be found at both ends and along all sides of the ear. Larvae feed until mature; they overwinter as fifth-larval instars in stalks and plant debris.


European corn borer larva (photo courtesy of Marlin Rice, Iowa State University).


European corn borer injury to corn ear (photo courtesy of Marlin Rice, Iowa State University).

Fall armyworm. Like the corn earworm, fall armyworm moths migrate north into Illinois each year. Fall armyworms are a concern for cornfields from mid- to late summer. They cause serious leaf-feeding damage and feed directly on corn ears. Late-planted or later-maturing hybrids are more susceptible to fall armyworm injury. Most common is pretasseled corn. Larvae consume large amounts of leaf tissue, but as corn plants develop, larvae move to the ear. Unlike the corn earworm, the fall armyworm feeds by burrowing through the husk on the side of the ear. Larvae also enter at the base of the ear, feeding along the sides and even tunneling into the cob. They usually emerge at the base of the ear, leaving round holes in the husks.


Fall armyworm larva.


Fall armyworm injury to ear.

Western bean cutworm. A mid- to late-summer pest of corn, western bean cutworm moths begin to emerge in early July. Though some leaf feeding occurs, larvae feed primarily on silks, tassels, and developing kernels. Larvae of the western bean cutworm are not cannibalistic, and several larvae may infest one ear. Entry to ears is gained through silk channels or by chewing through husks, injuring the tip, base, and sides of the ear. Larvae feed on kernels until about mid-September, when they exit through husks. Reports of western bean cutworm injury have been very sporadic the past couple of years.


Western bean cutworm (photo courtesy of Marlin Rice, Iowa State University).


Western bean cutworm injury to corn ear (photo courtesy of Marlin Rice, Iowa State University).

Any one or combination of the aforementioned insects could be the cause of the injury being seen in cornfields. As much as we would like to be able to pinpoint the direct cause of injury, that is often impossible this late in the season. Summer scouting is the key to determining the potential insect culprits.

 

(Updated from 2005 article)