Additional Authors: Marian Luis and Maira Duffeck
Wheat is now between boot and anthesis (flowering) across the state. In most of the fields that we have visited over the last two weeks, the crop looks excellent, with very little or no disease symptoms on the flag leaf or even the two leaves below the flag leaf. In southern Ohio where the crop is at anthesis or will reach anthesis this week, the risk for head scab is very low (http://www.wheatscab.psu.edu/). This is largely because of the cool weather conditions we have experienced over the last several days. Head scab and most of our economically important diseases usually develop best under warm, wet, or humid conditions. Cool conditions have prevented or slowed down the development of diseases such as Stagonospora leaf and glume blotch.
However, as conditions warm up and wheat in the central and northern portions of the state reach anthesis over the next two weeks, the risk for head scab will likely increase, and with it comes the risk of grain contamination with vomitoxin. The fact that several corn fields across the state were affected be Gibberella ear rot last season could increase the risk for head scab and vomitoxin in wheat, especially if the variety is susceptible and conditions become warm and stay wet during and shortly after anthesis. Remember, Gibberella ear rot and head scab are caused by the same fungus. Even if wheat is planted into a field that did not have Gibberella ear rot last year, spores can still be blown in from fields with infested corn stubble and infect heads in wheat fields.
Priority should be given to a fungicide application program for head scab and vomitoxin control. Fungicides such a Prosaro, Caramba, and Miravis Ace as most effective against head scab and vomitoxin when applied at or shortly after anthesis. In addition, applying these fungicides at anthesis (flowering) will also provide very good control of late-season diseases such Stagonospora and rust. In a year such a this during which early-season conditions were not favorable for foliar disease development, a single application of Prosaro, Caramba, or Miravis Ace at anthesis should be sufficient to suppress head scab and vomitoxin and control foliar diseases. However, the opposite is not true. Applying these fungicides at or before heading will not provide adequate control of head scab and vomitoxin.