The wheat crop in Ohio is now at or just past Feekes 8 (flag leaf emergence), the growth stage at which we usually recommend fungicide application for foliar disease control. However, conditions have been fairly hot and dry over the last 7 to 10 days, slowing down the development of early-season diseases such as powdery mildew and Septoria. Septoria tritici leaf spot usually shows up first on the lower leaves as yellowish flecks that later develop into irregularly-shaped, brownish-gray lesions, with dark-brown to black spots in the center. The disease is usually spread from the lower to the upper leaves by rain splash; so, unless it rains and becomes cool (50 to 68oC) over the next week or so, Septoria leaf spot may not become a problem this year.
Cool temperatures and high relative humidity are also required for the development of Powdery Mildew, another early-season disease that so far is at very low levels this season. As it warms up, both Septoria and powdery mildew will become even less of a concern, but continue to monitor your crop over the next several days. Remember, if the variety is susceptible and conditions become favorable, a fungicide can be applied to prevent the diseases from reaching the flag leaf (the upper-most leaf of the plant) before grain-fill. Follow the link for fungicide options and also see the chart below.