Down with DON: a clear corn crop

Toxin levels are lower this year thanks to weather and farmer and supplier vigilance

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The Ontario corn ear mould and mycotoxin survey showed levels are considerably lower than 2018 with 96 per cent of samples testing less than two parts per million of deoxynivalenol (DON).

OMAFRA field crop specialists, Grain Farmers of Ontario and members of the Ontario Agri-Business Association collaborated to complete the survey.

Why it matters: Farmers were hit hard by DON in fall of 2018, downgrading the quality of large amounts of the corn crop, placing them on high alert for this corn season.

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A total of 222 ear corn samples were collected from October 3 to 9, 2019 from across the province. Five consecutive ears were collected from four random locations throughout fields and placed in high-temperature driers immediately. Dry ears were shelled to create a sample, then coarsely ground and mixed for sub-sampling consistency. The sub samples were collected and finely ground for DON analysis by quantitative ELISA analysis at the University of Guelph, Ridgetown Campus mycotoxin lab.

The results showed 84 per cent of the samples had less than 0.50 ppm DON concentration, 12 per cent 0.50 to less than two ppm, four per cent two ppm to less than five and finally, zero per cent five ppm and greater.

These results are much lower than 2018, which showed 33 per cent less than 0.50 ppm, 27 per cent 0.50 to less than two ppm, 15 per cent two to less than five ppm and finally 25 per cent five ppm or greater.

2019 brought quite the challenge for corn growers across the province, with a wet spring and a dry summer. Thankfully as farmers head into corn harvest, the DON levels seem to be lower than usual, thus far.

For the few farmers within the Chatham area who have begun to harvest corn, (as of October 17), the levels for DON seemed to be running around one or just below one, says Bob Thirlwall, market development agronomist with DeKalb.

Thirlwall’s territory runs between Windsor and Simcoe and he has yet to see ear moulds that bring a concern.

Ben Rosser, corn specialist with OMAFRA, says he is seeing the same results.

“Visually, samples are much cleaner-looking than last year, especially in southwestern Ontario and more in line with what ear samples would normally look like, visually speaking,” he says.

Rosser says weather played the biggest role in what farmers are seeing in this year’s crop.

“I think one part of the weather story is that we didn’t have the widespread frequent rainfall and moisture in the corn crop from silking through grain fill in 2019, like we had in 2018,” he says.

Thirlwall says management also is a factor that helped with this outcome.

“I think it’s a combination (weather and management), weather has a big impact for sure, and this year, because of what we experienced a year ago, a lot of (farmers) were targeting their fungicide timing at silking and they were using the right fungicides — the triazoles,” he says.

Although, 96 per cent of the samples tested below two ppm, the lowest it’s been since 2013, growers still need to be vigilant. Corn ear moulds and mycotoxins occur every year within Ontario and farmers still need to assess fields individually.

“Have a look at the samples, peel back some husks and (watch for) that pink mould. That is the one that gives us the biggest concern, gibberella ear rot is what can produce the DON in our corn samples,” says Thirlwall.

Unfortunately, if farmers are presented with infected corn, it’s advised to adjust the combine allowing for infected, lighter kernels to be thrown out the back. This keeps them out of the sample and it’s best to evaluate the samples from that field at your local elevator.

“If you suspect you have some ear mould, it’s also a good idea to keep that (infected corn) separate in your bins if you can, it gives you an opportunity to manage any dirty corn after harvest and reduce your risk at the end user,” says Thirlwall.

Being prepared

DON will continue to be a concern for farmers when choosing their corn in the years to come. Starting with the variety when choosing your 2020 crop is where to start.

Seed companies are understanding this concern for farmers and beginning to incorporate it into their seed guides.

“In the DeKalb agronomic chart, in our seed guide, we have a tolerance rating to Gibberella Ear Rot, another agronomic detail to look at, once you have selected your hybrid maturity, then you can look and narrow down your hybrid choices using the Gibberella rating,” says Thirlwall.

As well, the Ontario Corn Committee has conducted inoculated DON trials for hybrid DON ratings across a range of hybrid maturities at Ridgetown and Ottawa.

Ben Rosser notes it as an additional resource for farmers and expects it to be released at near the end of November.

Collecting corn samples

It is important farmers collect a representative sample, as 90 per cent of variability associated with testing comes from incorrect sample collection, says Ben Rosser in a recent article on Field Crop News.

Taking a sample from the top of a storage bin, truck or combine is not accurate as mycotoxin is rarely distributed evenly within a load.

When taking samples from a bin, truck, V-box, or other stationary loads, a sample probe is recommended. Ten probe samples is recommended, five samples minimum, is recommended.

If dealing with a moving stream of grain, use a diverter or randomly collect cups full.

Whichever method of sampling, it is important that the sample be processed quickly – the longer the sample is around the greater the potential for inaccurate results.

About the author

Reporter

Jennifer lives on a farm in Cayuga, Ontario and has a lot of experience in the many aspects of agriculture.

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