Few DON Concerns with 2025 Ontario Corn Crop

There appears to be virtually no concern with elevated vomitoxin levels in this year’s Ontario corn crop. 

Released last week, the results of the annual Ontario corn ear mould and mycotoxin survey showed 98% of the total 231 samples taken from corn fields across the province tested below 0.5 parts per million for deoxynivalenol (DON). That compares to the 10-year average of 86% and makes 2025 one of the lowest DON level years of the past decade.    

Just 10% of the 2025 samples tested from 0.5 to below 2 ppm, and 2% from 2 to less than 5 ppm. Only a single sample came in at 5 ppm or higher. 

Last year, roughly three-quarters (76%) of the 261 total samples tested below 0.5 ppm. 

The 2 ppm level is generally considered the maximum threshold at which DON levels are not a significant quality or marketing concern. The much larger percentage of this year’s crop below that level indicates producers should not run into grade discounts, depending on the possibility of localized hotspots. As shown on the map below, the higher DON readings were found in the southwestern part of the province, including Oxford County. 

“Even with 98% of 2025 samples testing below 2 ppm, growers should still be vigilant, as they may have individual fields with elevated DON,” the survey report said   

One of the worst years for DON levels in the Ontario corn crop was 2018. In that year, just one-third of the samples tested below 0.5 ppm, while 25% were at 5 ppm or above. A significant portion of the 2018 crop turned out to be virtually unmarketable, costing producers millions of dollars in lost sales. Farmers experienced another difficult year for DON in 2016, when less than half of the samples tested at 0.5 ppm or below.