This article was written by Dr. Bob Hunger, Extension Wheat Pathologist
Department of Entomology & Plant Pathology
Oklahoma State University – 127 Noble Research Center
Powdery mildew (Figure 1) is showing up on lower leaves in fields and trials around Stillwater, and I have also had reports of powdery mildew on lower leaves from Extension Educators around the state. I also have seen ‘hot spots’ indicative of barley yellow dwarf (Figure 2) around Stillwater, but did not find any aphids associated with these spots. From Texas, Dr. Clark Neely(Small Grains and Oilseed Extension Specialist; Texas A&M AgriLife Extension) relayed to me on April 4 that, “Overall, I think we have avoided the stripe rust and what little was around is shutting down now. Leaf rust is around, but seems lighter than normal for the moment.” Across Oklahoma, wheat leaf and stripe rust still are largely absent, although a few “stripes” of stripe rust were found by Zack Meyer here at Stillwater this morning at an Extension Educators in-service training. This lack of the rusts in Oklahoma is supported by the recently implemented scouting program involving Oklahoma Extension Educators. This program asks county educators to look for and report weekly the occurrence of stripe rust, leaf rust, and/or powdery mildew they observe in commercial fields, variety trials, or variety demonstrations located in their counties. This information is reported by county educators from counties across southern Oklahoma to Heath Sanders (Area Extension Agronomy Specialist; southwest district), from counties across mid-Oklahoma to Zack Meyer (Extension Educator; Kingfisher County) and from counties across northern Oklahoma to Josh Bushong (Area Extension Agronomy Specialist; northwest district). The incidence and severity of these three wheat foliar diseases can then be more accurately summarized and disseminated to facilitate decisions related to applying a fungicide to help manage these diseases on susceptible varieties. For the week ending on April 5, observations reported from across southern and mid-Oklahoma (Jackson, Dewey, Washita, Blaine, and Kingfisher Counties) indicated no leaf or stripe rust and only one report of powdery mildew on lower and mid-leaves in Washita County. It is still a bit early for reports to come in from across northern Oklahoma. Thanks are extended to all the educators that participated in this pilot program, and I would encourage more participation to facilitate this reporting program.
Figure 1. Powdery mildew observed April 5 on lower leaves of wheat in trials around Stillwater, OK.
Figure 2. Likely barley yellow dwarf (BYD) “hot spot” observed on wheat in early April (top photo). As time proceeds, these hot spots will develop stronger symptoms of BYD including leaf discoloration ranging from yellowing (middle photo) to purpling in some varieties (bottom photo).