Breaking down DON, drought and the 2018 corn season

A review of the corn season in Ontario and Manitoba and answers to 10 grower-submitted questions.
Top Crop Manager
Monday, 17 December 2018
By Top Crop Manager
Giberella (far left) is the corn ear mould responsible for DON.
Giberella (far left) is the corn ear mould responsible for DON. Photo courtesy of Ben Rosser.
From drought-like conditions in Manitoba to DON challenges in Ontario corn, Top Crop Manager tackled the highlights of the season in its Corn Season in Review webinar. Ben Rosser, corn specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and Morgan Cott, field agronomist with the Manitoba Corn Growers Association provided summaries of the corn season and answered producers' questions. 

Manitoba
Conditions in Manitoba have been dry over the last two years and 2018 was no different, Cott told webinar attendees. The province received half the normal amount of precipitation expected and conditions were extremely dry, resulting in earlier-than-average planting. “It was dry and warm and pretty much gravy going into planting season,” Cott said. However, the dry conditions persisted resulting in low soil moisture levels and poor seed-soil contact. There was a lot of variation, even within a field, and Manitoba corn experienced uneven germination and emergence. However, the dry conditions meant weeds were slow to emerge, and overall, the crop looked good. The tasseling stage came seven to 10 days ahead of normal, and during the VT and R1 stages – when corn requires the most water – Manitoba got “pure heat.”

By mid-August, drought symptoms in corn were obvious. Stalks were weakening and lodging eventually occurred continuing throughout September. Grain corn reached physiological maturity ahead of normal and silage corn yields were average to above average. As of late November, 205,489 acres were reported harvested, representing 54 per cent of all the acres planted in the province. Around 243 acres were reported as unharvested; 2,988 acres reported as overwintered acres and 7,717 acres reported as alternate-uses. However, Cott noted this harvest data was only two-thirds complete as of Dec. 12 and a fuller picture could be painted at the end of December. Despite a lackluster year for corn, the provincial grain corn history shows an overall trend of increasing yield and acreage in Manitoba over the past decade.

Ontario
The province generally had a very dry start, with the exception of the far south in Essex and Kent counties. June saw some rainfall, but large parts of Ontario didn't experience lots of moisture until August. Most of the province was above normal in crop heat units. There were variable planting conditions throughout the province, and around mid-May, many areas were ranging from 50 per cent to nearly complete in planting. Planting was delayed until the end of May and beginning of June for some areas with heavier soil and frequent rains. Rosser shared the results from OMAFRA’s Pre-Sidedress Nitrate Test (PSNT) survey, which showed that generally, soil nitrate levels were trending above average. When conditions are warm and dry, this is normally good for mineralization.

Western bean cutworm, a previously increasing issue in Ontario, was an anomaly in 2018 with less pest pressure and lower-than-normal trap counts. Rosser explained there could be more than one reason for this. First, peak moth flight was after corn had already tasseled. Generally moths try to avoid laying eggs in fields that have tasseled and go on to look for other late planted fields or bean fields. While it’s still speculative, Rosser also said that there has been some talk about natural enemies like ladybugs starting to pick up on the Western bean cutworm larvae.

Ontario saw fairly low disease pressure, but the challenge came later in the season with ear mould issues. Late rains in late July and August brought a lot of humidity to the corn canopy, which held moisture and was conducive to mould growth. Since 2011, OMAFRA has been conducting its Grain Corn Ear Mould and DON survey but Rosser noted, “this year things were definitely elevated." Just under 20 per cent of grower samples tested over five parts per million (ppm) for mycotoxins such as DON, a vomitoxin that is harmful when fed to livestock. When compared to longer-term averages, the amount was larger than what is typically seen, but Rosser explained 2018 was similar to 2006, Ontario's last high-testing year. London and the Middlesex County area were hot spots for ear mould, but high samples were found elsewhere too.

“Not all ear moulds are created equal, especially from the mycotoxin perspective,” Rosser explained. Some ear moulds produce mycotoxins and some don’t. Rosser broke down four ear moulds and what they produce:
  • Gibberella: The mould of main concern in Ontario and where DON comes from. This mould also produces Zearalenone and T2. It is a cooler moderate temperature disease and responds well to wetter conditions.
  • Penicillium/Trichoderma: This mould does not produce DON but does produce ochratoxins, which are a storage mycotoxin issue rather than a field mycotoxin issue.
  • Diplodia: This mould does not currently have known mycotoxin issues.
  • Fusarium: This is a different Fusarium mould than what Gibberella is and can produce fumonisin. Fumonisin is not an issue from a livestock feeding perspective but can be a potential carcinogen. From a grain handling and safety perspective, it’s important to take precautions such as wearing dust masks, washing hands after handling corn and reducing exposure. This mould thrives in hot dry weather and is more common in the United States Corn Belt.
Despite DON challenges, excellent yields were reported in many areas. The drawn out harvest as a result of wet and snowy conditions also presented challenges.

Questions
Are there any new solutions to preventing mycotoxins that are becoming a problem? - Bayfield, Ont.
Ben: Yes, I wouldn’t say new solutions but certainly there are a lot of management strategies. I would say weather is probably the biggest factor in terms of mycotoxin issues, that’s one thing that’s out of our control, but the next one is hybrid selection. There are no truly resistant hybrids out there, but there’s certainly a lot of variability in tolerance or susceptibility. So trying to choose a hybrid that’s more tolerant would go a long way.

There are some management options in terms of fungicides. There are two products that are registered to suppress ear moulds: Proline and Caramba. Both are triazole fungicides and the application timing is very important if you’re going that route. What you’re looking for is to try and protect those silks. In order to reduce silk infection, the optimum timing is when the silks have fully emerged from the ear but they haven’t started to change colour and dry up yet. If you go when silks are just starting to emerge, you might not get good silk coverage on the silks that haven’t emerged yet. If you go too late, the silks have already started to dry up or change colour. It might be too late and your mould is already established, so ideally fresh green silks that have fully emerged from the ear is the optimal timing for fungicides. Particularly Gibberella is what we’re going after, the ear mould hijacks the reproductive process, so just like how pollen will land on those silks and fertilize the kernels, the spores from the mould will also land on the silks, it will grow down to the tip of the ear, establish there and then start to spread down the ear. So really we’re trying to protect those silks to prevent the hijacking from the ear mould.

Another strategy is planting multiple hybrids. There have been cases with some growers who had one hybrid across a large amount of their acreage, and in some cases those individual hybrids turned out to be very bad. So maybe selecting multiple hybrids to spread out some of that risk, from a hybrid or genetics perspective, would be one more defensive play against ear moulds and mycotoxins.

2. Has there been any data about the effectiveness of these fungicides, Proline and Caramba, to reduce DON levels?
Ben: Yes, there was a bunch of work done at Ridgetown College (the University of Guelph Ridgetown Campus). Art Schaafsma and Dave Hooker had done a fair amount of work looking at those [fungicides] for ear moulds. So there definitely is data out there, and I think some of that work helped those products become registered for suppression for ear moulds. There definitely is data that can be dug up if someone is looking for it.

Editor’s note: Several of Art Schaafsma and Dave Hooker’s DON/corn studies are available through ResearchGate, such as the “Effect of Bt-Corn Hybrids on DON Content in Grain at Harvest” and the “Effect of Prothioconazole Application Timing on Fusarium Mycotoxin Content in Maize Grain.”

3. What are some future opportunities and concerns for growing corn in Western Canada? - Lacombe, Alta.
Morgan: In Manitoba, we’re so fortunate because we have this warm hub in southern Manitoba that seems to be extremely different from the rest of the Prairie provinces, or at least from what I know of. Moving out west as heat units or accumulation of heat units start to get a little smaller, the growing season gets shorter or a bit more variable from year to year, that question is more important on a year-to-year basis. So as the potential of corn moves west, we’re relying on these earlier hybrids that the seed companies are coming out with because that’s going to be a game changer. It becomes more of a question if those hybrids are going to be adapted to suit your area. So it’s going to be a lot of test running to see if what you’ve been provided with, will work. Have these hybrids been tested on different soil types and day lengths, and everything else we have to consider? If you are a producer from the west and thinking about getting into it, I recommend starting on a small acre basis and seeing how that goes for you. We do have some hybrid options to start with that are around the 70-day maturity or 2000 heat unit maturity, which is extremely low. The yield potential probably won’t be as great, so hopefully that builds over time, but it’s certainly a good starting point.

4. Are more volunteer corn issues expected in 2019 due to the late harvest and cold, wet conditions experienced in Ontario? - Waterford, Ont.
Ben: If you have delayed harvest, there’s been more lodging, you may be having ear drop that you wouldn’t have had with an earlier harvest. Again some of the ears or kernels going out, are, instead of it being warm enough like it would be earlier in the season; they could potentially germinate, freeze off, and die. Potentially that could be an issue as well. There are products registered for volunteer corn control, but yes, if harvest loss has been higher it could be something to watch for in 2019.

5. What are your tips for growing corn in a dry season and managing drought? - Vulcan, Alta.
Morgan: This question is a little bit heartbreaking to answer. It’s hard for me because after a couple of years of these drought conditions in Manitoba we’re seeing a complete depletion of soil moisture. It’s really hard to know what we’re going to get out of this winter, or the fall, so it really depends on what kind of moisture or precipitation we’re accumulating in this period and what’s going to be left or available for spring time. To be honest, if we were starting 2018 over again, or 2019 in very similar dry conditions, I’d be really hesitant as a corn producer to be putting all my original acres back into corn. I wouldn’t go all out, because there’s still a great chance that we get moisture during the season, but it’s such a gamble because we didn’t get any this year. We just missed every rain that seemed to be in the sky, it just shrivelled up into nothing, and corn can’t produce if it doesn’t get moisture. So if you’re really unsure going into the spring if there’s adequate moisture in the soil already, and if we will get enough in the following month to at least start a crop, I’d scale back on my acres just because we don’t know what might happen. Depleted and poor yields this year are the result of the drought, so it would only get worse going forward. We have gotten a lot of moisture this fall, but it’s not made up for everything that we have lost in the past couple months. Unless you have irrigation, I don’t really have tips for a drought, it’s a bummer you can’t control.

6. A lot of places dealt with snow, do you have suggestions for unworked fields this fall?
Morgan: There’s not much we do in the current time that would help with it, so just hope for an early spring.
Ben: It would depend on what your next crop is. Assuming it’s soybeans, response to tillage in soybeans could be pretty variable. I know if you talk to Horst Bohner, soybean specialist at OMAFRA, generally yield response tends to be fairly low but there are exceptions when it could be higher. So maybe if it’s a soybean situation, you could get away with it. If you are going back into corn, certainly corn-on-corn is more responsive to tillage. But there’s no option at all this fall for you, your options in spring might depend on your soil type in terms of what you’re able to get away with next spring in terms of tillage.

7. How do we handle tillage on our fields this coming spring that have many ruts created from wet weather this fall from equipment? - Sarnia, Ont.
Ben: I think [if] the ruts are fairly shallow, and you just need a levelling out for equipment next spring. I know growers that get away with some lighter vertical tillage passes. If there’s really heavily rutted areas, or specific areas of the field like where wagons or trucks were coming out, maybe some of those local areas you could hit a little bit more with some vertical tillage machines. If there are heavy ruts across the whole field, then maybe you are stuck doing heavier tillage or more primary tillage to try and remove those ruts if you’re still able to get in this fall.

8. Can you address the variability of trial results in a lack of moisture year like this one? What does a lack of moisture mean for trials? - Carman, Man.
Morgan: We were concerned about the results of our Manitoba Corn Committee trials, but it also goes for any trials around, and how you take those results and make something out of them. Where it's a very dry year or a very wet year, it adds greater variation to your data and makes it a little bit more unreliable. In the end, as someone who is analyzing that data, it just gives you instability with the level of data that you get, and so it’s hard to put out to the public as something reliable. Now if it’s consistent data, we want everybody to take it and run with it, because dry here is dry everywhere, and even if the yields are poorer or the moisture is poorer, that’s still great information. [But] when we see the differences between the ranges and we get more stats on it, then we have to omit the data because it’s not useful to a producer. We have to compare it to other situations and what we would do in that situation, and in this year we had to omit some of our trials because of the poor coefficient of variance, because it wasn’t reliable for people.

9. How many years is recommended before returning to corn or wheat after a high DON-level field? Is a two-year soy potentially a good idea? - St. Isidore, Ont.
Ben: Risks could be elevated a little bit because we have more residue out there, but I don’t think inoculum is typically a limiting factor when it comes to ear moulds or Fusarium head blight in Ontario. It really comes down to when you get those right environmental conditions. I think in a lot of fields that inoculum load is there, so I wouldn’t necessarily recommend trying to avoid a rotation as a management strategy. There is a bit of elevated risk but I’m not sure that [avoiding a rotation] would necessarily reduce things a lot, especially when there are rotational benefits from a yield and soil health resiliency perspective as well and nutrient cycling that have been shown with some of the rotation trials in the province. I wouldn’t necessarily go that route to try and reduce [DON risk]; I think there are other options and other tools that could be used from a management perspective.

10. As we go forward with higher-yielding crops and corn specifically, are there any major or minor nutrient application trends (either nutrient(s) or placement) do you see making a major impact on not only corn yield but corn quality? - Goderich, Ont.
Ben: Continue to watch your standard fertility, don’t forget about that or leave that on the table if you are going to change some other things. I think there are lots of questions about sulphur because our atmospheric deposition is decreasing, but yields are continuing to increase so maybe that’s one to watch. There have been a number of soil and crop trials, and some OMAFRA trials done in the past couple of years, where it’s still kind of a hit-or-miss and in some years there is a response. There are some growers that see a benefit to it, and others who do not. Beyond that I don’t have any major comments on trends, it’s still basic agronomy from a nutrient perspective.

Morgan: The biggest thing we’re trying to do in Manitoba is apply topping up methods with our nitrogen in crop, and that would just be an early top up around V6 or so. Some growers use drop nozzles and some are knifing it in, but some growers are adopting the Y-drops and the 4R strategies (right source, right rate, right time, right place) . . . especially because you can do that more than once instead of going in early, so that’s pretty exciting and I think the growers that are doing [Y-drops] are quite happy with it. So definitely more and more topping up in our acres. We’re also in the process of updating our nitrogen requirements for corn and we’re pretty excited to see what data [John Heard] comes up with because it’s a game changer because if we’re looking at possible 150-200 per bushel yields in good years, that’s a lot more or a lot less fertilizer that you need to be putting down depending on what kind of soils you’re on.

Editor's note: The responses to attendee questions have been edited and condensed for clarity. The full recording of the Corn Season in Review webinar will be made available here.

There are two webinars left in Top Crop Manager’s webinar series. On Jan. 16, Brian Beres, with AAFC Lethbridge, and Graham Collier, from the University of Alberta, will discuss their research showing that spring wheat can go in the ground earlier than traditionally recommended. On Feb. 6, Gary Peng from Agriculture and Agri-Food Canada Saskatoon, will present new information regarding blackleg management and control strategies in canola. The Early Seeding Dates for Spring Wheat webinar has been approved for one CCA-CEU in Crop Management and the New Strategies for Blackleg Management webinar has been approved for one CCA-CEU in Integrated Pest Management.

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