Wet conditions have stalled corn and soybean planting but may be ramping up the risk of foliar disease in wheat.
Ohio’s wheat crop is either at or past Feeke’s Growth Stage 10 (boot) and now is the time to scout fields if you have not already. Foliar diseases like Septoria leaf spot and powdery mildew thrive in cool, wet conditions and can potentially reduce grain yield and quality by damaging the flag leaf. When scouting for Septoria leaf spot, look for irregular brown blotches that may become bleached in appearance and contain small, blackish dots (fungal fruiting bodies). The main sign of powdery mildew is fluffy, whiteish-gray powdery growth (called pustules) on the leaf surface and lower stem. As the pustules age they will become covered with black dots on the surface.
As temperatures increase this week, keep an eye out for other potential foliar diseases such as Stagonospora leaf blotch and leaf rust. Stagonospora leaf blotch symptoms develop when temperatures are between 68- and 81-degrees Fahrenheit and typically appear as brown, lens-shaped lesions surrounded by yellow halos. Leaf rust also prefers warmer temperatures coupled with rainy, humid conditions and can be diagnosed by its round, orangish-red pustules scattered across the leaf surface.
If disease is present and conditions remain favorable for further disease development, consider a fungicide application between Feekes Stages 8 through 10 to prevent disease from reaching the flag leaf. Fungicide options can be found at https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-wheat-diseases.
Once wheat reaches flowering, Fusarium head blight or head scab becomes the main concern. Risk for head scab infection and deoxynivalenol (DON) contamination is greatest when wet, humid conditions coincide with flowering. To estimate the risk of infection in your area, utilize the Fusarium Risk Assessment Tool just prior to flowering. It is available at http://www.wheatscab.psu.edu/ If a susceptible variety is planted and the risk of FHB is moderate to high, consider a fungicide application of Prosaro, Caramba, Proline, or Miravis Ace at Feekes Growth Stage 10.5.1 (early flowering, Figure 3) or within the first 4 day after Feekes 10.5.1.