It’s time to start scouting your wheat for diseases if you haven’t already!

The wet, humid weather we’ve had in Tennessee can promote disease development  and as wheat approaches the flag leaf to boot growth stages (Feekes 9-10), scouting for disease is critical to determine if a fungicide application is necessary to protect yield.

The last leaf (flag leaf) to emerge from the whorl is very significant, because it makes up approximately 75 percent of the effective leaf area that contributes to grain fill. Hence, a diseased flag leaf equals yield loss.

To identify the flag leaf split the stem above the highest node. If no additional leaves and the head are found inside, than the flag leaf is confirmed.

To protect the flag leaf from disease timing is critical, because if a fungicide application is made too early, the flag leaf will not be protected and if too late, disease may develop to the point that a fungicide application would not be effective.

The decision to apply a fungicide to wheat should be based upon multiple factors including: 1) disease presence, 2) fertility and yield potential, 3) weather conditions and 4) cropping history.  

For example, a fungicide application would be warranted if:

• Disease is present;

• Nitrogen has been applied and the wheat has good yield potential;

• Weather conditions favor disease development (dependent on the disease, but most are favored by wet, humid conditions like we have had recently in Tennessee);

• Wheat has been planted in the field in the past year or two.