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Low level of DON in 2019 grain corn

Low level of DON in 2019 grain corn

Dry weather at the right time across much of Ontario prevented ear mould from developing

By Jackie Clark

Farmers harvesting grain corn this year are seeing significantly less ear mould than 2018, resulting in lower concentrations of harmful mycotoxins like DON (deoxynivalenol). This result can be attributed to weather conditions and selection of resistant hybrids, said Greg Stewart, the agronomy lead at Maziex.

 “The season-to-season difference is driven by rainfall and humidity right around pollination, silking, and early grain fill, where silks are susceptible to getting infected by ear mould spores,” he explained to

“Last year was the perfect storm in terms of frequent rainfall and high humidity. This year, at the end of July and early August, it was much drier.”

The high levels of ear mould and DON concentrations in 2018 made it easier for industry stakeholders to identify susceptible and resistant hybrids that fall.

“Seed companies and farmers were a little more attentive to hybrids that were more sensitive to mould and some of those hybrids didn’t get planted as broadly this year,” Stewart said.

“This year, things were so clean, so it’ll be more difficult” to observe hybrids with susceptibility or resilience to mould development, he said. Seed companies “have to move to some sort of artificial inoculation to test the hybrids,” he added. 

When selecting hybrids for next year, farmers will “have to rely on homework done by seed companies to evaluate how hybrids stack up,” Stewart said. Additionally, farmers may investigate fungicides that target ear moulds, he added.

But “the fact that (DON concentrations are) low, generally speaking, should not lead farmers to think there is zero diligence required,” he explained. “In some fields where there is western bean cutworm or bird damage to ears, we are seeing a bump up in mycotoxins. Growers would still want to be attentive.”

Overall, in this challenging harvest season, it is worth celebrating the lower risk of ear mould and the lower concentrations of mycotoxins. “Everyone is quite happy that it’s a year where the pressure was very low and most of their hybrids are clean,” Stewart said.

In total, 84 per cent of the 222 samples collected and tested had less than 0.50 ppm DON concentration in the survey completed by OMAFRA with Grain Farmers of Ontario and members of the Ontario Agri-Business Association. Only 33 per cent of samples had DON concentrations that low in 2018. Last year, 25 per cent of samples had DON concentrations greater than 5.00 ppm, and no samples were found at that level in 2019.

dimid_86\iStock/ Getty Images Plus photo


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