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Ont. DON levels close to average

Ont. DON levels close to average

Only one out of 245 samples had more than five parts per million of the mycotoxin 

By Jackie Clark
Staff Writer

Field crop specialists from the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) collected 245 ear corn samples from across the province of Ontario, and found DON (deoxynivalenol) mycotoxin levels in 2020 are close to the long-term average.

OMAFRA representatives conduct this survey annually in the fall, collaborating with Grain Farmers of Ontario and the Ontario Agri Business Association. This year, 89 per cent of the samples tested less than two parts per million (ppm) for DON, a low level, which is similar to average results from the last ten years.

This year’s results are “certainly not (like) 2018 where there were fairly significant issues, especially in the southwest part of the province, a lot higher levels than we normally see,” Ben Rosser, the corn specialist for OMAFRA, told

2020 DON levels were “a little bit higher than what we saw last year, but I think last year was probably one of the cleanest years we’ve ever seen in the ten years of doing our DON survey,” he added. “Like most years, there’s usually some DON somewhere. Some areas got the right combination of weather to allow (mould) to establish, and stayed wet to continue to grow.”

The crop experts identified some samples with elevated DON, but nothing abnormally high, Rosser said. “We only had one sample that was above five ppm.… There was a smattering across the province” of samples between two and five ppm.

The timing of moisture over the growing season may be the reason for these results.

Similar to 2018, from planting to silking, most of the province experienced fairly dry weather, Rosser explained. “Once we got to silking and tasselling timing, the taps really started to turn on for large parts of the province – which is great from a corn yield perspective because that’s when (corn is) most susceptible to drought stress.”

However, “that’s also when we get the initiation of infection for ear moulds. When you have fresh silks out in the field, spores can land on those silks and establish infection on those ears,” he added.

Moisture allowed for some moulds to establish, but drier weather toward the end of summer likely kept DON levels from getting too high, he said.

Because very few fields had DON present in 2019, farmers and agronomists may have had a difficult time picking out hybrids with resistance to mould, or identifying those that are susceptible.

“I think this year where we’re kind of average, there’s maybe enough data that some of those hybrids that are known to be more susceptible to ear moulds, even in a year like this, would probably show up more,” Rosser said.

Farmers can scout fields “to see what visual mould levels look like. If you have the ability to actually test different varieties … that would give you an idea too,” he explained. “If you’re in an area that has hardly anything high testing, that’ll be a little tougher.”

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