I started this past week on Monday (13-May) at the variety trial at Chickasha, OK, where wheat was mostly full kernel watery to milky. Stripe rust was the most prevalent foliar disease, but overall was not extremely heavy in the variety trial. Septoria/Stagonospora was a close second to stripe rust, and actually was more widespread than stripe rust but for the most part was only on the lower and mid leaves. Leaf rust also was present, but overall seemed less than stripe rust. From Chickasha, I moved to Tipton, OK in southwestern OK where the wheat was mostly about soft dough. Leaves here were quickly turning and showed a combination of stripe rust, leaf rust, and Septoria/Stagonospora. However, varieties and lines with good resistance stood out. On Tuesday (14-May), I was at the field day near El Reno in central OK (25 miles west and a bit south of OKC). Wheat here was at the end of flowering to full kernel-watery. Overall diseases were light with Septoria/Stagonospora on lower and mid leaves and some stripe and leaf rust on upper leaves. Powdery mildew also was present, but mostly only on certain varieties. Next, a demonstration was visited near Minco, OK (about 20 miles west). This demo was planted quite late (early December), and was mostly at flowering. The foliar disease situation was basically the same, that is, some stripe and leaf rust along with some powdery mildew and Septoria/Stagonospora.
Finally, there may be some additional diseases to watch for this year given the extended cool and wet spring. This includes several diseases, but primarily bacterial streak (black chaff) and Fusarium head blight (head scab). Dr. John Fenderson (Technical Product Manager; Bayer Crop Science-WestBred) indicated on 9-May that he observed major infections of bacterial streak across central Texas. Dr. Brett Carver (OSU Wheat Breeder) also indicated seeing symptoms consistent with bacterial streak at the field day near Okmulgee in eastern OK earlier this week. Symptoms of bacterial streak are somewhat similar to Septoria/Stagonospora, and could be overlooked if both are present. However, the head symptoms should be more discernable, and currently I have not seen symptoms such as this across central and western OK.
Fusarium head blight typically occurs in eastern/northeastern OK every year, and this spring has been favorable for this disease. Wheat heads will be totally or partially bleached and contain shriveled and often pinkish or salmon colored seed. To get more information on head scab, see OSU PSS-2145 (Fusarium Head Blight (Head Scab) of Wheat: Questions and Answers – available at http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-6307/PSS-2145...) and OSU PSS-2136 (Considerations when Rotating Wheat behind Corn – available at http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-5436/PSS-2136...). Another outstanding resource regarding Fusarium head blight is the “Fusarium Head Blight Prediction Center” at http://www.wheatscab.psu.edu/. At this site there are resources describing the disease as well an assessment tool that can be used to help predict when spraying is critical to help prevent Fusarium head blight.
--Bob Hunger, Extension Plant Pathologist, Oklahoma State University
For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu
For the latest news and updates from the U.S. Wheat & Barley Scab Initiative, go to https://www.scabusa.org