By Pierce Paul, Extension Plant Pathologist, The Ohio State University
Due largely to rainfall, high relative humidity, and warmer temperatures over the last several days, the risk for head scab is now moderate across most of the state of Ohio, and high across the south. The risk is low in NW Ohio. This would be the time to consider applying a fungicide to control head scab and reduce the risk of grain contamination with mycotoxins as fields reach anthesis in the northern third of the state. Even fields in the lower half of the state that flowered 5 to 7 days ago could benefit from a fungicide application. Most of the recommended fungicides for FHB management provide similar levels of FHB and vomitoxin suppression when applied between early anthesis (Feekes 10.5.1) and early grain-fill (up to six day after early anthesis).
The recommended, and most effective, fungicides for scab and vomitoxin control are Miravis Ace, Prosaro, Caramba, Proline, Sphaerex, and Prosaro Pro. These products provide comparable levels of scab and vomitoxin suppression when applied at early anthesis or shortly thereafter. Applications made to wheat at early or full head emergence (between Feekes 10.3 and 10.5) may also suppress scab (compared to no fungicide at all), but tend to be considerably less effective against vomitoxin. Several of these fungicides are also very effective against leaf diseases, which are also on the increase in some areas. Please read product labels carefully before making an application, in particular, pay close attention to the preharvest intervals.