Wheat Fungicides Face Off Against DON and Damaging Scab

Small adjustments to fungicide practices can make a big difference

The Danger of DON

Twenty years ago DON was a term unfamiliar to most wheat producers, grain elevator personnel and wheat millers. Mycotoxin deoxynivalenol (DON) is a toxic substance produced by the fungus that causes a disease in wheat and barley known as Fusarium head blight, or "scab." In 1993 widespread infestation of 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.



In 1993 widespread infestation of 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.



FDA Guidelines for DON

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). Millers can set their own ppm requirements as long as the resulting product satisfies FDA guidelines.


Awned WheatDON and Fungicides

The best way for growers to manage and even reduce DON levels in their grain is through the application of a fungicide. But timing is key, and not all fungicides are created equal. “Growers might think the best way to fight fungal disease is to apply a strobilurin chemistry at flag leaf stage, but they might not realize strobilurin fungicides do not have activity against scab,” says Randy Myers, Ph.D., fungicide product manager for  Crop Science. “Strobilurin fungicides should not be used after flag leaf emergence if scab is a threat. Doing so may increase DON levels in the grain.”





“Strobilurin fungicides should not be used after flag leaf emergence if scab is a threat. Doing so may increase DON levels in the grain.”
– Randy Myers, Ph.D., fungicide product manager




The Problem with Strobilurin

Strobilurin fungicide is typically applied at wheat growth stage Feekes 8.0 to protect the flag leaf from foliar diseases. Scab isn't a threat until wheat reaches flowering, at Feekes 10.51. But it can take as little as a few days for wheat plants to grow from one stage to the other. “A grower may apply a strobilurin fungicide to manage disease of the flag leaf when his wheat is at Feekes 8 or 9,” Myers explains. “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.”



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



Disease and Scab Control with Prosaro®

Myers explains that the answer doesn't have to be complicated. “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 also points out, “they get all of the foliar disease control they expect from a strobilurin fungicide—along with scab control.” Universities conducting wheat research are emphatic that strobilurin fungicides are not effective against scab, while field trials show that Prosaro controls scab and reduces DON levels in grain. (Figure 2). Prosaro does more than help a grower manage DON levels—it also increases his yield (Figure 3), and helping maximize yield potential means a grower can get a premium price for his grain, further increasing his profits.


Works Cited

  • Results from 31 winter wheat trials conducted 2008-10 in IN and OH. Prosaro applied at Feekes growth stage 10.51. (charts and graphs from original advertorial)

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