By Emmanuel Byamukama
Winter wheat is either at, or will soon be at, flag leaf. One field at Aurora Research farm had some wheat plants already at heading (Figure 1). Now is a good time to scout for foliar diseases and determine the need for flag leaf fungicide application. We have had a lot of moisture in the last seven days and these conditions may increase the risk for fungal disease development.
Figure 1. (Above) Winter wheat at Aurora Research Farm near Brookings beginning to head.
Winter wheat fields scouted last week had tan spot and Stagonospora/Septoria blotch beginning to develop in the lower canopy. Another disease that could develop is powdery mildew (Figure 2). All three diseases are promoted by dense canopy, wheat stubble, and extended leaf wetness. Rusts also have the potential to develop early this season. Both leaf and stripe rusts have been reported in Nebraska.
Figure 2. (Above) Powdery mildew on winter wheat. Powdery mildew will develop on lower leaves first because of prolonged leaf wetness and poor air circulation in the lower canopy.
If less than 50% disease incidence is seen on the second leaf below flag leaf, then fungicide application could be postponed while keeping an eye on weather and disease development till flowering. If wet weather is predicted around flowering, one triazole fungicide application can protect both the wheat heads from scab and the flag leaf from rusts and leaf spots.
Producers are encouraged to leave untreated stripe in the field in order to determine whether there was enough disease to warrant fungicide application. It may also help to point out if the fungicide type and dose worked as it was supposed to.
Source : SDSU