Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
Vol. 12, No. 21
Jun 6, 2013
Wheat Disease Update
Bob Hunger, Extension Wheat Pathologist
Not a lot to add since the last report and this is likely the last one from Oklahoma unless something out of the ordinary occurs. Wheat is being harvested in southwestern OK. I’ve heard reports that ranged from “about 180 bu from 50 some acres” up to around 30 bu/acre. Wheat around Stillwater is typically at medium dough with very little green leaf tissue left in the leaves. Stems are still mostly green but also beginning to fade. All of the wheat I looked at on Monday had 3 plump kernels/mesh.
A field day last Thursday (30-May) in Pawnee County (30 miles northwest of Stillwater) revealed a trial and surrounding field with severe leaf spot. Isolations from 3 varieties all yielded Pyrenophora (tan spot) and Septoria/Stagonospora with tan spot (Pyrenophora) more common than the other two. The wheat was approaching dough, so I don’t think there will be a huge yield hit – especially given the moisture and cool spell we have been having. I have only rarely seen tan spot and the leaf spot diseases in general this severe in Oklahoma.
Dr. Ned Tisserat (Wheat Pathologist, Colorado State University) confirmed our suspected diagnosis of bacterial streak/black chaff in the variety trial at Chickasha (about 40 miles southwest of Oklahoma City). [See: http://entoplp.okstate.edu/pddl/2013/PA12-17.pdf] Symptoms were widespread and quite severe across all varieties, but similar symptoms due to leaf spots, drought, and freeze also contributed to the overall burnt appearance to the trial.
Finally, Bryan Vincent (crop consultant – north central OK) sent in photos of isolated spots in a wheat field in Kay County (just south of Kansas in north central OK). Although no sample was submitted, the photos and description of the situation definitely indicated this to be take all.