This past week I had phone conversations with two individuals from southwestern OK. Both indicated they are starting to see a bit more rust (primarily leaf rust) across southwestern OK, and with wheat approaching heading they are considering making arrangements to spray.
Also early this past week, Robert Calhoun (Senior Agriculturalist, Plant & Soil Sciences, OkSU) found stripe rust at the Experiment Station located in north-central OK near Lahoma. Robert indicated the incidence of stripe rust was extremely low. Today (Friday, 19-Apr) I looked at wheat west of Stillwater to Hennessey (about 50 miles) and then north to Waukomis (about 20 miles). Wheat along this route and around Stillwater is between growth stages 9-10 (flag leaf fully emerged to boot stage). I didn’t see rust anywhere I stopped. I did see some tan spot in one field that had obvious wheat residue, and moderate powdery mildew on lower leaves in one field. By far the most common “find” was aphids – mostly bird cherry-oat, but also some greenbug. I observed some associated spots that I suspect are barley yellow dwarf, but these “spots” were fairly scattered and not numerous. Brian Olson (Senior Agriculturalist; OkSU) spent Friday morning spraying at the station near Lahoma and indicated he did not find any rust and that heads were not yet in the boot.
In summary, foliar diseases are still at low incidence across Oklahoma but there is the indication that leaf rust is increasing across southern OK. Given the present and short-term forecast for temperature and moisture, I expect leaf rust to increase. These conditions also are favorable for stripe rust and powdery mildew, but the seeming sparseness of these two foliar diseases at this point in time indicates that in a typical year we are more at risk from leaf rust than we are from stripe rust or powdery mildew.
--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