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Ontario Grain Farmer Magazine is the flagship publication of Grain Farmers of Ontario and a source of information for our province’s grain farmers. 

Is DON a concern?


CORN IS APPROACHING the pollination stage across the province. At this stage, we are reminded that the first infection of gibberella ear rot can occur if the viable silks are exposed to the right conditions. Weather at pollination becomes a critical key in the development of the gibberella ear mould and the production of DON toxins.


For the disease to develop, the three sides of the disease triangle (environment, pathogen, and host plant) must be present for the disease to establish. With DON production in corn, the host plant and site of entry is the corn silk channel, the pathogen gibberella, and the third side of the triangle is the environment/weather.

The environment/weather is the key variable. The highest infections of gibberella ear rot observed in labs, field trials, and farmer fields have been traced to when temperatures reach 27° C – 28° C with added humidity and moisture to keep the spores alive. If these weather conditions (moisture and temperature) continue, the development of gibberella and DON will be seen later through the ear development stage.

Farmers should keep an eye on the forecast as we approach the pollination period and be prepared to reduce the infection potential with a fungicide application that can help protect the plant and reduce the severity of the DON infection. 

Hot, dry weather will curtail gibberella infection and the potential of DON accumulation. In order to reduce losses due to DON, keep a close watch on all your fields and protect the highest at-risk fields (ones that pollinate in disease-favourable weather conditions) with a recommended fungicide for gibberella control. Speak with your agronomist about what fungicides are currently available. Publication 812: Field Crop Protection Guide 2021 (page 41) lists potential products that could be used. 

Marty Vermey is Grain Farmers of Ontario’s senior agronomist. Laura Ferrier is Grain Farmers of Ontario’s agronomist.


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