So far only the usual suspects of powdery mildew (when it was still cool) and now Septoria have been reported in Tennessee wheat.
Most wheat is at or has passed flag leaf, and with such low levels of disease present and stripe rust only confirmed in Texas and Louisiana to date, the next timing to consider fungicide application is bloom to protect from Fusarium Head Blight/head scab. While Miravis Ace can be applied at heading to provide protection from head scab, the best protection again mycotoxin levels at harvest are applying a non-QoI/non-strobie fungicide at beginning bloom. Products that contain a QoI/strobulirin can increase mycotoxin levels and should not be applied at heading or later.
Short descriptions of fungal wheat diseases which include conditions for disease development, symptoms and specific management options can be found along with images in the Fungal Wheat Disease Identification publication (https://extension.tennessee.edu/publications/Documents/W662.pdf) and at guide.utcrops.com (mobile friendly site). General disease scouting time line and guidance on timing of fungicide can be found in the UT Extension Wheat Disease Management publication (https://extension.tennessee.edu/publications/Documents/W663.pdf).
It’s best to first identify the disease you’re trying to management and then choose the best fungicide for the job. The wheat fungicide efficacy table, that university wheat pathologists across the nation contribute to, is a good source to match fungicide efficacy to specific diseases. Each state will have its own version of the table, here is the TN Wheat Fungicide Efficacy publication (https://extension.tennessee.edu/publications/Documents/W341.pdf) and the generic national one can be found at the Crop Protection Network.