Map: Survey Shows Low DON Levels in 2024 Ontario Corn Crop

An annual survey conducted by the province suggests few vomitoxin concerns with this year’s Ontario corn crop. 

Released this week, the results of the Ontario corn ear mould and mycotoxin survey showed more than three-quarters (76%) of the 261 total samples tested below 0.5 parts per million for deoxynivalenol (DON). Last year, only 41% of the samples tested below 0.5 ppm. At the other end of the scale, none of this year’s samples tested above 5 ppm, compared to 5% in 2023. 

All told, 94% of the 2024 samples tested at 2 ppm or lower, versus 77% last year and the 10-year average of 86%. 

The 2 ppm level is generally considered the maximum threshold at which DON levels are not a significant quality or marketing concern. The larger percentage of this year’s crop below that level indicates producers should not run into grade discounts, depending on the local severity of the problem. 

As the map below shows, the bulk of this year’s more elevated DON levels (between 2 and 5 ppm) showed up in pockets in the southwestern part of the province, including Middlesex, Oxford, and Elgin counties, although some cases in eastern Ontario were also identified. 

Farmers should evaluate their crops and consider harvesting and drying higher risk fields before infections worsen, the report said. Ear moulds and mycotoxins occur every year in Ontario and fields need to be assessed individually, it added.    

“Even with 94% of 2024 samples testing below 2 ppm, growers should still be vigilant, as they may have individual fields with elevated DON.”  

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.