Stagonospora leafspot on wheat
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Leaf spots abound on wheat across the state this season. A few weeks ago, it started dominating the leaf area to the point that it rendered some flag and #2 leaves incapable of providing much help to grain heads.
The two diseases that cause what is referred to as leaf spot are Septoria tritici and Stagonospora nodorum. In cooler seasons, Septoria is the major player; whereas in warmer seasons, such as this one, Stagonospora rules. What is troubling about Stagonospora is that it can readily move to the head causing glume blotch if wet weather persists. Glume blotch can lead to shrunken kernels and lowered test weights.
In 2008, Stagonosora leaf spot was common in the Thumb region. Conventional fungicides in a replicated trial gave a 7 bu/ac advantage when applied at flag leaf emergence and 4 bu/ac when applied at heading. This season, the disease is more severe (and widespread) and fungicide usage may prove even more advantageous, especially where glume blotch comes into play.
Of course, where there is one foliar disease there is often others. This season, some fields are hosting a moderate level of powdery mildew or rust along with the Stagonospora.