This week, wheat is heading or will begin to head in fields across Ohio, particularly in southern and early-planted fields. In fact, in some southern fields, the crop was at full head emergence (Feekes 10.5) at the end of last week (May 15-17) and will likely reach the flowering growth stage this week. This is the time to begin thinking about head scab and its management with fungicide. Heads are most susceptible to the scab fungus during flowering and infection is favored by warm, wet or humid conditions. Although, we have had frequent rainfall over the last few weeks and conditions have been fairly humid, most of the scab-favorable moisture occurred before flowering. In addition, temperatures have been cool across most of the state. This will likely reduce the risk of head scab. As indicated by the scab risk tool (www.wheatscab.psu.edu), for wheat flowering today (May 19), the risk of scab is low, and will likely continue to be low during most of this week. However, most of our crop will reach anthesis (flowering) within the next two weeks, during which time temperatures are likely to increase. This could increase the risk for scab, particularly if it continues to rain. Continue to use the scab prediction tool to monitor disease risk as the crop approaches this critical growth stage.
Source : osu.edu