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Strobilurin Fungicides Increase DON Levels in Wheat, Reduce Quality Small adjustment to conventional fungicide practice can reduce DON levels, increasing grain quality and profitability Twenty years ago terms such as vomitoxin or DON were unfamiliar to wheat producers, grain elevator personnel and wheat millers. However in 1993, widespread infestation of the mycotoxin deoxynivalenol (DON) occurred in grain produced in eastern North Dakota and western Minnesota, resulting in significant losses. Since then, DON has hit virtually every U.S. wheat-growing region. DON is a toxic substance produced by the fungus that causes a disease in wheat and barley known as Fusarium head blight, or “scab.” Because DON could pose a health risk if consumed in high amounts, the Food and Drug Administration (FDA) has set guidelines for maximum DON levels allowed in wheat products for human consumption and livestock feed. (Figure 1).

The application of a strobilurin fungicide around the wheat growth stage of Feekes 8.0 is intended to protect the flag leaf from foliar diseases. Scab isn’t a threat until the wheat reaches flowering, Feekes 10.51. But it can take as little as a few days for wheat plants to grow from one stage to the next. “A grower may apply a strobilurin fungicide to manage disease of the flag leaf when his wheat is at Feekes 8 or 9,” Myers explained. “Shortly thereafter, his wheat could be at Feekes 10.51—critical timing for scab prevention. That strobilurin, though, is ineffective when it comes to scab and could even increase mycotoxin levels. The grower has to decide if he’s ready to invest in the labor and fungicide to make another pass through his field to manage scab and protect grain quality.” Myers further explained the answer doesn’t have to be complicated.

Millers can set their own ppm requirements as long as the resulting product satisfies FDA guidelines. But they may pay a premium price for grain that already meets FDA guidelines, as it will require less processing to achieve an end product that meets regulatory thresholds.

“If growers can resist that urge to make a strobilurin application and wait just a few days to apply a product such as Prosaro fungicide,” Myers said, “they get all of the foliar disease control they expect from a strobilurin fungicide—along with scab control.”

The best way for growers to manage and even reduce DON levels in their grain is through the application of a fungicide. But growers need to remember that timing is key and not all fungicides are created equal.

Universities conducting wheat research are emphatic that strobilurin fungicides are not effective against scab, while field trials show that Prosaro® effectively controls scab and ultimately reduces DON levels in grain. (Figure 2).

“Growers might think the best way to fight fungal disease is to apply a strobilurin chemistry at flag leaf stage,” said Randy Myers, Ph.D., fungicides product manager for Bayer CropScience. “But they might not realize strobilurin fungicides do not have activity against scab. In fact, strobilurins applied at the wrong time can increase DON levels.”

Prosaro does more than help a grower manage DON levels—it also increases his yield. (Figure 3). This combination of protecting the plant from disease and helping maximize yield potential means a grower can get a premium price for his grain, thus further increasing his profits.

Figure 1



1 ppm

Finished wheat products, such as flour, bran and germ that potentially may be consumed by humans.

5 ppm

Grains and grain byproducts destined for swine, providing that these ingredients do not exceed 20 percent of the diet.

5 ppm

Grains and grain byproducts destined for all other animals, providing that these ingredients do not exceed 40% of the diet.

10 ppm

Grains and grain byproducts destined for ruminating beef and feedlot cattle older than 4 months and for poultry, providing that these ingredients do not exceed 50 percent of the diet. Figure 3

Figure 2

don level reduction with prosaro

Prosaro Increases Yield (Bu/A)

4.00 3.50

DON (ppm)



Results from 31 winter wheat trials conducted 2008-10 in IN and OH. Prosaro applied at Feekes growth stage 10.51.

89.3 Winter wheat



n=169 winter wheat trials conducted 2008-10 in OH, IN, KY, MO, MI, TN and IL. Prosaro applied at Feekes 10.51.




Spring wheat




n=28 spring wheat trials conducted 2008-10 in ND, SD and MN. Prosaro applied at Feekes 10.51.

0.50 0.00



Prosaro 6.5 fl oz/A

Bayer CropScience LP, 2 T.W. Alexander Drive, Research Triangle Park, NC 27709. Always read and follow label instructions. Bayer, the Bayer Cross and Prosaro are registered trademarks of Bayer. Prosaro is not registered in all states. For additional product information call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at CR0313PROSARA029V00R0




Prosaro 6.5 fl oz/A





2013 Prosaro® Fungicide - DON Reduction in Grain Crops  
2013 Prosaro® Fungicide - DON Reduction in Grain Crops  

Prosaro® does more than help growers manage DON levels—it also increases yield. This combination of protecting the plant from disease and he...