Corn
With a later than normal planting window and a summer growing season seemingly short on summer weather, some growers have been monitoring their corn growth stages and asking about gauging the risks associated with corn maturity and frost, particularly those who planted very late or have longer maturity hybrids. While there are still several weeks left to the growing season, a few things growers trying to gauge their crop stage for frost risk may want to consider include:

Crop Staging

Clearly, the closer to maturity (black layer) the crop is, the less impact a frost event will have on the crop. For quick review:

The emergence of silks is the R1 stage. As a rough guideline, once pollination occurs, it takes about 60 more days for the crop to reach physiological maturity. Thus, silk timing can give a bit of an indication of when maturity of the corn crop may be expected – a crop that pollinated around July 25th may be expected to reach maturity or black layer sometime around September 25th. While there can be some small differences across hybrid maturities, hybrid maturity ratings have a much more significant impact on the length of time in vegetative stages than reproductive stages.

The R2 blister stage occurs following pollination when fertilized kernels are just beginning to develop, while the R3 milk stage occurs when kernels are turning yellow and are beginning to fill with an opaque milky fluid. Grain fill is rapid by the R3 stage, and maturity under normal conditions would be 5-6 weeks away.

The R4 dough stage occurs when the milk solution turns pasty as starch continues to form, with some kernels beginning to dent as dough begins to turn to hard starch at the dent ends of kernels. Under normal conditions, the dough stage may be generally 3-5 weeks from maturity.

The R5 dent stage occurs when the majority of kernels have dented, and the milk line, which separates the hard starch phase from the soft dough phase, progresses from the dent end towards the cob. The dent stage may last approximately 3 weeks.

The R6 maturity or black layer stage marks physiological maturity. This occurs when a small layer of cells at the base of the kernel near where the kernel connects to the cob die and turn black, which marks the end of grain fill from the cob into the developing kernel. Maximum dry matter accumulation has occurred, so any frost or stress event after this stage will have little impact on yield unless harvestability is compromised. Black layer normally forms once milk line has reach the base of the kernel, although significant stress events (extended period of very cool average temperatures, significant defoliation) can result in black layer formation before the milk line has reached the base of the kernel.

Frost Severity

In regards to frost severity, a light frost (ie. 0°C) may damage or kill leaves, but not be cold enough, or last long enough to actually penetrate into the stem and kill the plant. While premature leaf death limits further grain fill from photosynthesis, a living stem can still translocate dry matter to the developing grain to continue to provide some grain fill after a light frost event.

In the event where temperatures are low enough (ie. -2°C), or last long enough to penetrate and kill the entire plant, there is no ability of the plant to continue filling grain, and yield at that point has been fixed.

Any frost event during the blister or milk stage would result in significant grain yield losses as significant grain fill is still yet to occur at these stages.

A light frost event at the dough stage may reduce yields by 35% while a killing frost may reduce yields by 55% (Lauer, 2004).

Yield loss in the dent stage depends on the relative time left to mature. A light frost at the beginning of dent stage may reduce yields by 25% while a killing frost may reduce yields by 40%. During the mid-dent stage, significant dry matter accumulation has occurred, and light and killing frosts may reduce yields around 5% and 10% respectively.

Estimating Time to Maturity

Time required to reach maturity can be estimated by knowing the approximate Crop Heat Units (CHU) required for each reproductive corn stage. A general approximation of CHU required to complete the various R growth stages in corn is presented in Table 1. Scouting corn for the crop stages described above and referring to Table 1 will give an indication of how many CHU are required for the corn crop to reach maturity.



Comparing the estimated CHU required from Table 2 to an estimated number of CHU available until typical first frost date gives an idea of how much CHU would be available in an “average” year, and how close to maturity the crop may be for the average expected first frost date. Typical first killing frost dates based on 30 year climate normal across a selection of locations in the Province are presented in Table 2, while CHU values can be estimated through calculation tables in the Field Scouting chapter of Pub 811 Agronomy Guide for Field Crops, or through other weather information providers such as Farmzone.com or WeatherCentral.ca.

This Report includes data from WIN and Environment Canada
It took a lot of work, but one young Manitoba grower and entrepreneur finally has the answers the customers of his short-line machinery business have been looking for.

Darren Faurschou has a diploma in agriculture and operates a family farm in the Edwin area, west of Portage la Prairie, Man. He also serves as president of the Faurschou Ag Center, which opened in April 2015 and retails air drills, precision planters and a line of independent corn headers that adapt to row spacing. Many customers question the benefits of planting corn with an air drill versus a planter, so last year Faurschou contracted with the University of Manitoba’s department of biosystems engineering to use his 125-acre field and his own machinery for an independent evaluation of row spacing and seeding systems for corn yield and rate of emergence.

Row spacing had four variations: 7.5-inch, 15-inch, 30-inch and paired-row (7.5-inch pairs, 30 inches on centre). Two seeders were used: a twin-row Monosem planter and a Salford 522 air drill.

There were eight treatments on the field; each treatment was repeated five times in the randomized experiment. The seeding equipment was adjusted to have a uniform two-inch seeding depth. Most plots were planted on May 8 and 9, 2016.

To produce the 15-inch and 7.5-inch plots, the planter drove over the field twice. The planter’s 7.5-inch plots were seeded on May 10 and 11, 2016, due to rain and time constraints.

Craig Heppner, a recent graduate from the University of Manitoba’s bachelor of science in biosystems engineering program took on the challenge of managing the 40 plots, recording data and processing the results as part of his undergrad thesis. Faurschou provided machinery, set up the field, supplied seed (Pioneer 7332) and was responsible for applications to protect the crop from weeds and disease.

“I went with the big field for plots because size is important,” Faurschou says. “If you’re out a point on a big plot, the impact is less. You are more accurate in your detail. Real machines – commercial equipment – do all the work in real-life scenarios. Things like dry spots and wet spots average out at the end of the day.”

To be sure the results were impartial, Faurschou asked the university to handle the data collection.

Results
Faurschou had expectations about the results, and some were proven. For instance, it’s tradition in southern Manitoba to plant corn in 30-inch rows with 7.5-inches between plants in the row. For decades, planters and harvest headers have been built for that 30-inch row spacing.

“I thought the paired-row on the [Monosem] planter would do the best overall. There’s a lot of research to show that, and it did beat the 30-inch single row,” Faurschou says.

The Monosem planter twin rows are 30 inches on centre; each seed row is four inches off centre.

But in each row-spacing comparison, the 30-inch row option had the lowest yield.

“I thought the 7.5-inch would be the best for the air drill, on the theory of narrow rows using more sunlight. What I found was, for the paired row, the 15-inch and the 7.5-inch trials almost filled the rows at the same time. The 30-inch never really did completely fill in,” he says.

Overall, the 15-inch spacing had the highest yield for both the air drill and for the planter.

“It ended up doing the best. I was really surprised by that,” Faurschou says.

Heppner’s detailed analysis, converted from metric, comes to this conclusion on corn yield: “When comparing effects of the seeders, average yield for the planter was 173 [bushels/acre] bu/ac compared to 161 bu/ac for the air drill. This translated to a 5.5 per cent difference in yield.”

“When comparing effects of spacing only, yield was found to be the highest for 15-inch plots at 173 bu/ac. The 7.5-inch plots were not statistically different than this at 168 bu/ac. The 30-inch and paired row plots were significantly lower at 162 bu/ac and 164 bu/ac, respectively.”

Heppner also notes the planter was much more uniform in seeding depth, as expected, and that the average seeding depth under the planter was about a quarter-inch shallower than under the drill. The rate of emergence for planter-placed corn also was faster.

Heppner concludes, “The planter provided more consistent seeding depth than the air drill, leading to faster speed of emergence, which induced a higher yielding crop. Also, 15-inch and 7.5-inch spacing produced higher yields than 30-inch and paired rows.

“The best-case spacing and seeder for south-central Manitoba in a year with similar environmental conditions would be a planter spaced at 15 inches.”

Answers and advice
The work required to run the 40 site trials on 125 acres was more than Faurschou expected. He estimates the time commitment was four to five times as much as he would have needed to plant and harvest a conventional field of corn.

However, now he has answers and advice based on science rather than experience and educated guesswork.

“There’s been a lot of discussion about planting corn with an air drill versus a planter. As for a replicated comparison in row spacing, with results for a planter versus air drill, I’ve never heard of that,” Faurschou says. “My theory was that there are benefits for an air drill in narrow spacing and benefits for a planter in wider row spacing, but there’s not a lot [of research] done on row spacing in corn in this part of the world.”

Now, according to Heppner, there is proven evidence that a planter will return more corn than an air drill and that row spacing returns more corn at 15 or 7.5 inches than it does at 30 inches.

Due to the explosion of soybean acres in Manitoba, many farms now have a 15-inch row crop planter in addition to an air drill. It was assumed – but not proven – that lifting every second seed run on the soybean planter would be the best practice for planting corn.

Still, many farms are equipped with only an air drill. Faurschou’s trials show that if the farm has an air drill with 7.5-inch spacing, simply putting a seed block on every second run can convert it for seeding 15-inch corn rows.

One caution with this, he notes, is that the Salford air drill used in these trials is a double-disc opener. Most air drills probably have only a single disc opener.

“With a single disc, you may not have the same depth control, so the results might be different,” he says.

After studying his results, Faurschou believes the evidence points to Manitoba corn being “happiest” on 15-inch spacing between rows and between plants. In this set of trials, that spacing allowed for the optimum use of available sunlight, moisture and nutrients and consistently produced the highest dry bushel yield.

The results give Faurschou some pretty clear-cut answers for anyone with questions about row spacing.

“For my customers, if they are going to plant corn with an air drill, I’m going to recommend 15 inches. If they’re going to buy a planter to use for corn and soybeans, I’m going to recommend that they buy a 15-inch planter for both,” he says.

There’s also an economy-of-scale factor. On 15-inch rows, Darren says the average yield advantage was 6.6 bu/ac in favour of the planter; the least difference was four bushels an acre.

Using the conservative numbers, Faurschou suggests the four-bushel yield advantage on $4 corn is almost enough to justify buying a planter if it’s time to replace or upgrade an air drill.

But, there’s more to consider.

“If you’re growing just a quarter of corn and you have an air drill that can do 15-inch spacing, that’s probably the way you should go,” he says. “If you have 1,000 acres of corn, then it would almost justify buying a planter.”

In all this, caution remains a good idea. Another trial conducted in another year and under different growing conditions might produce different results.

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Figuring out precisely how much nitrogen fertilizer Ontario farmers should apply to their grain corn is tricky business. For starters, nitrate – the form of nitrogen (N) in the soil that is readily available to plants – is highly mobile and susceptible to being leached away by rainfall. Therefore, the spring soil nitrate test that’s standard in Western Canada is not always useful in Eastern Canada, where rainfall tends to be heavier.
David Morris is not only secretary to the Ontario Corn Committee (OCC), which conducts the province’s annual hybrid corn performance trials. He’s also the committee’s “corporate memory,” having been involved for about 40 years.
Breeders continue to focus on early maturing hybrids and bring a variety of stacked traits to western Canadian corn growers. Seed companies have supplied Top Crop Manager with the following information on the new corn hybrids for 2017. Growers are advised to check local performance trials to help in variety selection. The listing is by ascending crop heat units (CHU).
Researchers in Penn State's College of Agricultural Sciences have received a $7 million grant from the U.S. Department of Energy's Advanced Research Projects Agency-Energy, or ARPA-E, to design a low-cost, integrated system that can identify and screen for high-yielding, deeper-rooted crops.

The interdisciplinary team, led by Jonathan Lynch, distinguished professor of plant nutrition, will combine a suite of technologies designed to identify phenotypes and genes related to desirable root traits, with the goal of enhancing the breeding of crop varieties better adapted for nitrogen and water acquisition and carbon sequestration.

The project is part of ARPA-E's Rhizosphere Observations Optimizing Terrestrial Sequestration, or ROOTS, program, which is aimed at developing crops that enable a 50 percent increase in carbon deposition depth and accumulation, while also reducing nitrous oxide emissions by 50 percent and increasing water productivity by 25 percent.

The ROOTS program website explains that while advances in technology have resulted in a tenfold increase in crop productivity over the past century, soil quality has declined, leading to a soil carbon debt equivalent to 65 parts per million of atmospheric carbon dioxide. This soil carbon debt increases the need for costly nitrogen fertilizer, which has become the primary source of emissions of nitrous oxide, a greenhouse gas. The soil carbon debt also impacts crop water use, increasing susceptibility to drought stress, which threatens future productivity.

Given the scale of domestic and global agriculture, there is tremendous potential to reverse these trends by harnessing the photosynthetic bridge between atmospheric carbon, plants, microbes and soil. Advanced root systems that increase soil organic matter can improve soil structure, fertilizer use efficiency, water productivity, crop yield and climate resilience, while mitigating topsoil erosion – all of which provide near-term and sustained economic value. | READ MORE
Douglas Cook at New York University and colleagues from the University of Nebraska are using special microphones to listen to corn plants in order to determine what leads to wind-induced corn stalk failure. It turns out, the sounds stalks make just before failure are very similar to the sounds made when breaking. "We now think that plant growth involves millions of tiny breakage events, and that these breakage events trigger the plant to rush to 'repair' the broken regions. By continuously breaking and repairing, the plant is able to grow taller and taller," says Cook. It's an idea that mimics the science behind how human muslces are built: Muscles are strengthened when tiny microtears are repaired after lifting weights. Although most of the work is still in the early stages, this marriage of mechanical engineering and plant science and the information gathered so far can help plant breeders design optimal, strong plants. | READ MORE 
Cool but dry conditions prevailed for the start of the corn growing season as May transitioned from a cooler than average April. May remained dry, with few precipitation events to delay planting. A few localized pockets in southern Ontario were the exception, which received regular rainfall during the first half of the month. Planting started in earnest in many areas during the middle to end of the first week of May and progressed quickly once started. Planting conditions were generally good, although some growers on heavier textured soils reported that slow drying of subsoils were holding off early planting until ground conditions were more fit. Planting was nearing completion in many areas by the end of the following week (May 14), but continued on some heavier textured soils as well as those areas that had been receiving rainfall. Statistics Canada estimated that 2.0 million acres of grain corn and 0.250 million acres of silage corn were planted in Ontario in 2016.

While lingering cool soil temperatures slowed development of the earliest planted corn, emergence was generally good for most fields. With the lack of rainfall in May, corn that had been planted when parts of fields were not quite fit or had not been fully planted into moisture may have struggled to emerge or emerged late. While generally minor overall, this resulted in variability in some fields. Some growers on heavier soils reported emergence issues following the cool weather and rainfall of May 14-15th. A small amount of replanting was reported to have occurred.

The annual OMAFRA Pre-Sidedress-Nitrate-Test (PSNT) survey was conducted at the V3-V4 stage on June 6-7th. With an overall average soil nitrate concentration of 11.2 ppm, levels were average to slightly higher than average. Given the lack of rainfall and low potential for soil saturation during May and June, nitrate losses from leaching or denitrification were unlikely. Below average precipitation in June maintained a wide window for weed control and sidedress nitrogen applications. With the exception of some moisture stress appearing on soils with poor water holding capacity in the drier parts of the province, the corn crop generally looked good and uniform through the end of June.

While some parts of the province received rain in July, many areas continued to be below normal, particularly the Bruce-Grey, Niagara and Central Ontario regions. Fields or parts of fields in these regions were beginning to show signs of moisture stress as corn leaves would wrap. There were some concerns as corn entered the moisture-sensitive tassel and pollination stages during the hot and dry conditions around the week of July 18. Some localized areas received thunderstorm related precipitation around this period.

During grain fill, there were reports of “tip-back” where several rows on the cob tips failed to pollinate and silks remained green. Warm temperatures continued to push crop development. As corn continued the grain filling process, significant rainfall events started to occur during August, with monthly precipitation totals ranging between 100-200 per cent of normal for large portions of the province. Despite this, leaf diseases, where present, typically remained at low levels. Between timely planting and above average heat unit accumulation, there were few concerns about crop maturity as August came to a close.

Silage harvest started in earnest in many areas during the week of September 12, with the exception of some early harvesting of moisture stressed crops. September remained generally dry, which resulted in good silage harvest conditions. Some reported whole plant moisture being drier than what had been anticipated at the start of harvest. Yields were reported to be below average in areas with little rainfall and on soils with poor water holding capacity, while yields in other areas were reported to be average. Lab analysis results suggested vomitoxin levels in silage were higher than normal. 

The annual OMAFRA grain corn vomitoxin survey was conducted from September 23 to 30th. The survey indicated elevated vomitoxin levels with 26 per cent of samples testing above two ppm. Long-term averages for this category run between five and 10 per cent, suggesting some extra monitoring for grain management and feeding may have been required in 2016. Risks may have been elevated from the wet and humid conditions that persisted from August to early September. Poorer pollination of ear tips which resulted in silks remaining green and husk tips that tended to remain tight may have also contributed to this. Western bean cutworm feeding that opened husks for mould establishment was prevalent in many areas as well. The incidence of samples testing higher for vomitoxin decreased east of Toronto.

As the growing season came to a close, heat unit accumulation ranged from average to 100-200 Crop Heat Units (CHU) higher than normal. Coupled with dry weather, corn harvest started early with some combining beginning as early as the last week of September. Harvest started in earnest around October 15, and progressed quickly as dry conditions prevailed for most of the province, resulting in a wide harvest window. Most growers reported moisture levels lower than what was typical for the time of year, and excellent test weights. With the exception of some localized pockets where soybean harvest was delayed, harvest was wrapping up in most areas by the end of the first week of November. Many growers reported yields that were above expectations considering the hot, dry growing season, with the exception of those on soils with poor water holding capacity, or regions which received well below average precipitation. As of December 14, Agricorp corn yields have been reported on 78 per cent of insured acres with an average yield of 167 bu/ac. This compares well to the 10 year average yield of 167 bu/ac for those reported acres.

Researchers at the University of Missouri have determined the mechanisms corn plants use to combat the western corn rootworm.

The Ontario Corn Committee has released results from the 2016 Hybrid Corn Performance Trials. | READ MORE
Bt corn has been on the market in Canada for over a decade; last year, Bt corn hybrids were planted on 3.1 million acres across the country. 

The technology is incredibly, and increasingly, valuable to Eastern Canadian growers, where 2,035,000 of the total 2,295,000 acres of corn were planted to Bt hybrids in 2015. But the ever-present risk of the development of insect resistance to the technology is keeping the industry on its toes.

While resistance hasn’t yet developed in European corn borer (ECB) populations in North America, reduced susceptibility has been noted in some populations of corn rootworm, according to Jocelyn Smith, a research associate in field crop pest management at the University of Guelph’s Ridgetown Campus.

But resistance can be delayed with proper management. In Canada, stewardship of Bt technology takes the form of insect resistance management (IRM) plans, which chiefly involve maintaining refuges to delay the development of resistant insect populations. 

Stewardship also entails rotation of traits in the field, as well as the use of stacked traits.

“The most important thing we can do with this issue is educate growers more about the risks they’re taking if they continuously use traits for rootworm,” Smith says. “Their sheer numbers and biology give them advantage.”

This is a message familiar to Eastern Canadian corn producers, and they’ve taken it to heart. The Canadian Corn Pest Coalition (CCPC) – made up of academics (such as University of Guelph researchers), the Canadian Food Inspection Agency (CFIA), the provincial ministries of agriculture, and industry representatives – has been conducting surveys on insect resistance management compliance since the late 1990s. 

Until 2012, those surveys were conducted in alternating years with CFIA IRM compliance surveys, but that year, stewardship compliance rates were so high CFIA discontinued them unless “in future, industry practice shifts from using blended refuge.”

But the CCPC’s bi-annual survey continues. “The increase in compliance with refuge area requirements from 2013 to 2015 occurred in all three provinces and now stands at 91 per cent in Ontario, 90 per cent in Quebec and 91 per cent in Manitoba,” the 2015 report concluded.

According to the same report, compliance tended to be higher in the 35 to 44 age category, but lower among producers who believed stewardship requirements to be “only somewhat important.” In addition, the report indicates awareness of stewardship requirements has declined since 2013, particularly in Ontario; compliance was also lower among those who believed they did not understand requirements.

More education needed
Cindy Pearson, national manager of the CFIA’s Plant Biosafety Office, says the onus is on companies marketing Bt products to educate producers regarding the need for delaying resistance and how refuges work.

“IRM plans are the responsibility of the company to whom the Bt corn product has been authorized, and CFIA receives specific reports from companies that
detail their various activities on that front,” Pearson says.

The survey notes refuge-in-a-bag (RIB) hybrids, which contain the required percentage of refuge seed, resulted in significantly higher compliance rates after their market introduction several years ago. The market has also changed with the introduction of stacked hybrids with multiple Bt traits or modes of action against the insect pests.

“There are currently three traits available for corn rootworm control,” she says. “Where we have growers with long-term use of two of those traits on their own (not in a stacked product), we’ve started to
notice some shifts in susceptibility when we test those populations in the lab.”

This doesn’t necessarily mean producers can see resistance developing in the field, but it’s still a red flag.

“We need to focus on informing continuous corn growers that the three-year limit is important,” Smith says. “We may have had a situation where a grower has used a single trait for years and it’s compromised, so then when they use the stack there’s only one viable trait remaining against the pest.”

Smith also emphasizes monitoring as a key aspect of stewardship. “If you are growing corn on corn, scout your corn late in the season and if there’s less than one beetle per plant you might be able to get away without using transgenics,” she says. “You might be able to hold off on using some of the technology in the following year.”

Smith also recommends rotating management options — in other words, soil insecticides and Bt traits.

“And again in season, keep an eye on the pest situation in the crop. For ECB and rootworm, you need to monitor whether they are being controlled by the Bt hybrids or not. If they are not, you need to notify the CCPC and the trait provider,” she says.

As long as they use Bt technology, producers are on notice to use it well. Resistance is in nobody’s interest except the insects.

The OMAFRA field crops team conducted its annual vomitoxin survey to assess the presence of corn ear mould and grain vomitoxin in the 2016 corn crop. Vomitoxins can be produced by Gibberella and Fusarium ear moulds and can be disruptive when fed to livestock, particularly hogs.

A total of 121 samples were collected from southern to eastern Ontario from Sept. 23 to 30. In most cases, five consecutive ears were pulled from four random locations throughout a field. After recording pictures and rating ears for the presence of moulds and insect or bird feeding, samples were placed into driers as soon as possible after collection. Dry ears were shelled and mixed through a sample splitter, and delivered to SGS Agrifood Laboratories in Guelph for vomitoxin (DON) analysis.    

Results
Of the 121 samples collected:

  • 48 per cent (58) had a DON concentration of less than 0.5 ppm;
  • 26 per cent (31) had a DON concentration between 0.5 and 2.0 ppm;
  • 26 per cent (32) had a DON concentration of 2.0 ppm or greater

Visual mould symptoms were much more prevalent in the 2016 survey than what has been observed in recent years. Similarly, vomitoxin analysis revealed DON concentrations that were higher than surveys from the past couple of harvest seasons, with the most recent year of comparable results being 2011 (Table 1). These results suggest extra vigilance in monitoring and managing DON concentrations in corn may be required in 2016. While some samples with elevated levels of DON were present across most regions sampled, in general there appeared to be a greater incidence of elevated DON levels for samples collected from southwestern Ontario.

Table 1. Vomitoxin (DON) results from the past six OMAFRA vomitoxin surveys.

DON Concentration

2016

 2015

 2014

 2013

 2012

2011

< 0.50 ppm

48%

75%

  66%

84%

85%

75%

0.50 to <2.00 ppm

26%

20%

  25%

14%

11%




≥  2.00 ppm

26%

5%

9%

  2%

4%

24%


Feeding damage
Feeding on ears by pests, particularly western bean cutworm (WBC), incomplete pollination, and open ears present an opportunity for greater mould infestation. While visual mould symptoms were generally more severe where ear feeding from WBC was present, mould symptoms and elevated vomitoxin levels were also observed on some ears and samples with little or no feeding injury. While WBC feeding may predispose risk, monitoring will be important in a higher risk year such as 2016 whether or not WBC feeding was present.

Going forward
This survey does not fully capture all regions of the province, and results can vary locally from field to field depending on hybrid, planting date, insect feeding or fungicide practices. These results may not fully capture what is occurring in your fields, and therefore monitoring is recommended. If you suspect grain vomitoxins may be present, it is recommended to sample ears in a similar fashion as described above, hand shell, mix, and submit a grain sample as soon as possible after collection to one of the several labs in the province that test for vomitoxin.

When ear rot is present, the following harvest, storage and feeding precautions are advisable (Adapted from OMAFRA Pub 811, Agronomy Guide for Field Crops):
  • Harvest as early as possible especially susceptible hybrids.
  • If insect or bird damage is evident, harvest outside damaged rows separately. Keep and handle the grain from these rows separately.
  • Adjust harvest equipment to minimize damage to corn, and to remove smaller end kernels or those that have been damaged from mould or insect feeding. Clean corn thoroughly to remove pieces of cob, small kernels and red dog.
  • Clean bins before storing new grain and cool the grain after drying. If possible, segregate corn based on vomitoxin content to help match end use.
  • Check stored grain often for temperature, wet spots, insects and mould growth.
  • Exercise caution when handling or feeding mouldy corn to livestock, especially to hogs. Pink or reddish moulds are particularly harmful. Test suspect samples for toxins. Work with a nutritionist to manage vomitoxin levels in feed. 
Acknowledgements
Appreciation to the Grain Farmers of Ontario and SGS Agrifood Laboratories in Guelph for their support of this survey and analysis, and to the OMAFRA field crops team, industry participants and growers that assisted in the co-ordination and collection of samples. 

As corn producers plan for harvest, they should be accessing their fields for stalk rot and ear moulds, reminds the OMAFRA Field Crop team. The distribution and prevalence of these diseases vary from year to year but they are present every year, especially when the crop is under stress (water stress, insect feeding, etc.). It goes without saying that this year was very stressful and in many cases, corn plants had to endure not one stress but multiple stresses and we are observing ear mould infections (Gibberella and Fusarium primarily) in many fields across the province. They range from light to significant levels therefore, in order to manage and minimize the effects of these ear rot diseases, it is critical to assess fields before harvest. Growers should assess fields each year, because these pre-harvest assessments can alert them to potential problems and provide time for livestock producers for example, to segregate, obtain alternative grain, or hold onto stored corn from the previous year.

Scouting practices are similar for all corn ear rots. Begin scouting fields at late dent stage to determine their presence and severity. When scouting, randomly select plants and pull back the husk to examine the entire ear. A quick method is to select 100 plants across the field (20 ears each from five different areas). For each ear, be sure to peel back the husks and examine the entire ear. Fields with 10 per cent of ears having significant mould growth should be harvested sooner than later.

Leaving diseased grain in the field allows the ear rot fungi to keep growing, which will increase the risk of mouldy grain and mycotoxin contamination. Most ear rot fungi continue to grow (and, if applicable, produce mycotoxins) until the grain has less than 15 per cent moisture. In severely infected fields, it may be worthwhile to harvest grain at higher moisture and then dry it to less than 15 per cent to minimize further mycotoxin accumulation.

Preventing ear rots and mould is difficult since weather conditions are critical to disease development. Although some tolerant hybrids are available, none have complete resistance. Crop rotation can reduce the incidence of Diplodia ear rot. Cultural practices have been shown to have limited success in preventing ear and kernel rots. Minimize these diseases through timely harvest and proper drying and storage.

When ear rot is present, the following storage and feeding precautions are advisable:

  • Harvest as early as possible.
  • If bird damage is evident, harvest outside damaged rows separately. Keep and handle the grain from these rows separately.
  • Adjust harvest equipment to minimize damage to corn. Clean corn thoroughly to remove pieces of cob, small kernels and red dog.
  • Cool the grain after drying.
  • Clean bins before storing new grain.
  • Check stored grain often for temperature, wet spots, insects and mould growth.
  • Control storage insects.
  • Exercise caution in feeding mouldy corn to livestock, especially to hogs. Pink or reddish moulds are particularly harmful. Suspect samples should be tested for toxins.
It is critical to identify ear rots in the field because many of the fungi responsible for these diseases produce toxic chemicals (known as mycotoxins), which can harm livestock and humans. Grain that has been contaminated with mycotoxins can be difficult to market and may be docked in price. Management begins with proper identification so how can a grower tell the difference between these ear moulds.

Gibberella ear rot: The most common and important ear mould in Ontario is Gibberella zeae which is the sexual reproductive stage of Fusarium graminearium. This fungus not only infects corn, but also small grains such as wheat, and can survive on soybean roots. In most cases, Gibberella begins at the ear tip and works its way down the ear. Also, the husks from infected ears are often tightly adhered to the ear. Although the fungus can produce a white-coloured mould, which makes it difficult to tell apart from Fusarium kernel rot, the two can be distinguished easily when Gibberella produces its characteristic red or pink colour mould. Infection begins through the silk channel and thus, in most cases starts at the ear tip and works its way down the ear. In severe cases, most of the ear may be covered with mould growth. Corn silks are most susceptible two to 10 days after initiation. Warm and wet weather during this period is ideal for infection.

Fusarium kernel rot: Unlike Gibberella, Fusarium infected kernels are often scattered around the cob amongst healthy looking kernels or on kernels that have been damaged by corn borer or bird feeding for example. Fusarium infection produces a white to pink or salmon-coloured mould. A "white streaking" or "star-bursting" can be seen on the infected kernel surface. Although many Fusarium species may be responsible for these symptoms, the primary species we are concerned about in Ontario is Fusarium verticillioides (formerly Fusarium moniliforme). Fusarium survives in corn debris. The significance of this fungus is that it produces a toxin called fumonisin that has been shown to cause cancer in humans. The environmental conditions that favour disease development are warm, wet weather, two to three weeks after silking.

Diplodia ear rot: The characteristic ear symptom of Stenocarpella maydis and S. macrospora infection is a white mould that begins at the base of the ear and will eventually cover and rot the entire ear. Mould growth can also occur on the outer husk which has small black bumps (pycnidia) embedded in the mould. These reproductive structures are where new spores are produced. Pycnidia (the small, black, spore-producing structures of the fungus) overwinter on corn residue and are the source of infection for the subsequent corn crop. Dry weather before silking, immediately followed by wet conditions, favour Diplodia infection.

Penicillium ear rot: Penicillium rot (Penicillium oxalicum) produces a light blue-green powdery mould which grows between the kernels and cob/husk surface. Infected kernels could become bleached or streaked. Penicillium ear rot can be a serious problem if corn is stored at high moisture levels (greater than 18 per cent).

Table 1.  Common ear rots and moulds that occur in Ontario and the primary mycotoxins they produce.

Ear Rot

Mycotoxin
produced
Favourable environment

Signs and symptoms
Aspergillus Aflatoxin Hot, dry Olive green spores on ear
Fusarium Fumonisin

Moderate to warm temperatures during silking, 

wet periods prior to harvest

White to purple mold, scattered across ear;
Starburst pattern in kernels
Gibberella Deoxynivalenol (vomitoxin) and zearalenone Cool, wet weather Pink to white mycelial growth
Diplodia None currently known in U.S. and Canada Moderate temperatures and wet during silking White mycelial growth on ear and husk; black pycnidia in cob
Penicillium Ochratoxin (only some species) Wet, humid conditions post grain-fill Blue-gray fungal spores
Nigrospora None Damaged corn Black spores, grey mycelia, shredding cob
Cladosporium None Wet weather near harvest Dark-green to black kernels
Trichoderma T-2 (only some species) Damaged corn Blue-green spores growing in and on kernels; may cause sprouting


More information can be found in OMAFRA’s Field Crop Agronomy Guide – Publication 811, or Crop Protection Network Publication “Corn Management Disease Series – Ear Rots” at CropProtectionNetwork.org.
Sept. 14, 2016 - At a critical stage of development this growing season, corn and soybean plants didn’t get one essential ingredient for growth – moisture.

The dry, hot summer, with drought-like conditions that persisted well into August, will reduce yields for both crops, says Henry Van Ankum, chair of the board of the Grain Farmers of Ontario.

He has a large-scale corn, soybean, and wheat farm of his own near Alma, north of Guelph.

While it is the case that certain pockets of land in the Guelph area will yield better than others, and that conditions in the fields are variable, it is safe to say that this will not be a banner year for growers, Van Ankum indicated.

“It’s really variable, depending on your soil type,” he said. “But certainly on your gravely soils around Guelph, it was definitely too dry at a critical period, when the corn was tasseling and the cob was pollinating. There won’t be a fully formed cob on some of that corn.” | READ MORE.
Sept. 3, 2016 - “If we grow successfully here, then the dairy farmers can feed (it) to the animals and then that way they can get more milk,” said Mumtaz Cheema, and agronomist at Grenfell Campus, Memorial University of Newfoundland in Corner Brook.

Friday, Cheema and four students working on the project visited the corn plots they are growing at the Forestry and Agrifoods Agency’s Western Agriculture Center and Research Station in Pynn’s Brook.

The project, in its second year, involves the study of five silage varieties of corn, a crop that provides high energy for dairy cows.

“The objective is to find a good variety that can be successfully grown here,” said Cheema, standing in front of row after row of tall corn stalks.

The research is also to determine which varieties have the capability to get more nutrients from the soil. | READ MORE.
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