Wheat Nearing Critical Growth Stage, Growers Can Use Scab Forecasting System to Determine if Fungicides Are Needed


WOOSTER, Ohio – Wheat in Ohio is nearing the critical flowering growth stage, and with rainfall and drastic temperature changes forecast for the next few days, some growers are concerned about disease development, according to a wheat expert from Ohio State University’s College of Food, Agricultural, and Environmental Sciences.

While wet, humid conditions during flowering can lead to head scab development, the forecast for cooler temperatures over the next several days should help to slow down this disease, said Pierce Paul, an Ohio State University Extension wheat researcher.

At this point, much of Ohio’s wheat is in good shape and likely to continue flowering during the last week of May, which is the critical stage when people are concerned about disease development, said Paul, who is also a plant pathologist with the Ohio Agricultural Research and Development Center.

OSU Extension and OARDC are the outreach and research arms, respectively, of the college.

“While head scab does not develop every year, wet, humid weather during flowering can contribute to its development in some areas this season,” he said. “Therefore, to control this disease, growers need to apply either Prosaro or Caramba fungicides at flowering.

“Fungicides are most effective against scab and vomitoxin when applied at flowering. Earlier applications will provide adequate control of Septoria and Powdery mildew, but will not control scab.”

To assess the risk for scab and determine whether a fungicide application at flowering is warranted for scab control, growers should use the Wheat Scab forecasting system, http://www.wheatscab.psu.edu, which is up and running and available for use in Ohio, Paul said.

Frequent rainfall always puts the crop at risk for head scab development and vomitoxin contamination of the grain, but these will only become a concern if it continues to rain during flowering and temperatures increase, he said.

“This is because the wheat plant is most susceptible to scab during flowering, and the scab fungus infects and causes the most damage when warm, wet or humid weather coincides with flowering,” Paul said. “The cooler conditions forecasted to occur over the next few days can slow the disease down and is good for grain development.

“But growers should also keep their eye on the scab forecasting system, which is still the best way to forecast risk in their area. If the forecasting system indicates that the risk is moderate to high, then you should apply the fungicide.”

To use the system, growers need to select wheat type (winter) and their flowering date, which is the day when anthers are first seen sticking out of the heads. Color patterns across Ohio and neighboring states will then indicate the level of risk in the region for the flowering date selected, he said.

Red indicates a high risk, followed by yellow for moderate risk and green for low risk, Paul said. 

Tracy Turner
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Pierce Paul